Aural devices, aural systems and methods relating to same

Abstract

A personal acoustic device with passive noise blocking or noise attenuation characteristics for use in high noise environments or for acoustic isolation from an external environment allowing for continuous sound blocking without any power or additional infrastructure. Passive systems have limited ways to fail versus active systems such as active noise cancellation with their complexity that can fail unexpectedly or are unavailable when power is absent. The device comprises an outer cup with an inner cup connected by one or more elements for at least one of locating, retaining and limiting motion of the inner cup with respect to the outer cup, wherein the inner cup fits over a user's car.

Description

AURAL DEVICES, AURAL SYSTEMS AND METHODS RELATING TO SAMEFIELD OF THE INVENTION

[0001] This patent application relates to personal acoustic devices and more particularly to personal acoustic devices with noise blocking or noise attenuation characteristics and more particularly to designs and methods of implementing passive personal acoustic devices with noise blocking or noise attenuation characteristics discretely or with active augmentation or with additional acoustic elements.BACKGROUND OF THE INVENTION

[0002] Aural health is important to individuals as oral communication is a major means of communication between individuals or in other contexts such as enjoying audiovisual content. Significant effort has been expended in developing headphones with improved ergonomics, improved audio reproduction etc. However, these developments do not address the provision of improved protection for a user’s ear drum in high noise environments or providing acoustic isolation for the user from the external environment if they wish to concentrate, sleep etc. Further, recent developments have focused on active noise cancellation increasing the complexity of headphones which only offer benefit whilst they have power and do not provide good acoustic isolation, particularly at higher frequencies.

[0003] Accordingly, it would be beneficial to provide users with improved passive acoustic attenuation which provides superior hearing protection for high noise environments (e.g. factories, construction sites, airports, concerts, shooting ranges, military contexts, racetracks etc.). Passive systems offer limited ways to fail while active systems are complex and can fail unexpectedly. Accordingly, passive acoustic attenuation provides standalone devices which do not require electricity or any infrastructure and can block sound non-stop without interruption.

[0004] Additionally, improved passive acoustic attenuation devices can also provide users with means for enhanced concentration for working or studying, especially in distraction heavy environments (e.g. cubicles, trading floors, coffee shops etc.) as well as superior sound isolation to avoid human sleep disturbances etc.

[0005] Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to mitigate limitations within the prior art relating to personal acoustic devices and more particularly to personal acoustic devices with noise blocking or noise attenuation characteristics and more particularly to designs and methods of implementing passive personal acoustic devices with noise blocking or noise attenuation characteristics discretely or with active augmentation or with additional acoustic elements.

[0007] In accordance with an embodiment of the invention there is provided a personal acoustic device comprising:an outer cup having a defined geometry and an opening;an inner cup having another defined geometry and another opening where a portion of the inner cup is disposed within the outer cup; andone or more elements at least one of locating, retaining and limiting motion of the inner cup with respect to the outer cup; whereinthe inner cup fits over a defined portion of the user’s ear.

[0008] In accordance with an embodiment of the invention there is provided a headset for a user comprising:a band for fitting to a portion of a user comprising a personal acoustic device for attenuating sound to an ear of the user over a frequency range of interest; whereinthe personal acoustic device comprises:an outer cup having a defined geometry and an opening;an inner cup having another defined geometry and another opening where a portion of the inner cup is disposed within the outer cup; andone or more elements at least one of locating, retaining and limiting motion of the inner cup with respect to the outer cup; andthe inner cup fits over a defined portion of the user’s ear.

[0009] Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:

[0011] Figure 1 depicts an exemplary wireless portable electronic device supporting communications to a network and other electrical devices according to and supporting embodiments of the invention;

[0012] Figure 2 depicts bands of frequencies associated with typical human hearing;

[0013] Figure 3 depicts a plot of sound transmission loss (STL) versus frequency for a generic sound barrier and an inset of a simplified STL versus frequency plot for the generic sound barrier;

[0014] Figure 4 depicts simplified STL versus frequency plots with respect to the effect of material stiffness on the STL and shifting the resonant frequency of a sound barrier;

[0015] Figure 5 depicts simplified STL versus frequency plots with respect to the effect of material stiffness on the STL and shifting the resonant frequency of a sound barrier;

[0016] Figure 6 depicts a simplified STL versus frequency plot outlining the design methodology of increasing mass and reducing resonant frequency for increased STL for aural devices according to embodiments of the invention;

[0017] Figure 7 depicts STL versus frequency for mechanically dislocated walls with varying air gap for aural devices according to embodiments of the invention;

[0018] Figure 8 depicts design variations of multiple walls with equal total mass per unit area and total wall depth for aural devices according to embodiments of the invention;

[0019] Figure 9 depicts a profile of a rectangular ear cup, an ear cup geometry of an embodiment of the invention and prior art ear cup geometries of commercial headphones;

[0020] Figure 10 depicts schematics of varying ear sealing geometries for personal acoustic devices (PADs) according to embodiments of the invention;

[0021] Figure 11 depicts a schematic of an assembly and prototype image for a laminated PAD according to an embodiment of the invention;

[0022] Figure 12 depicts a design of PAD according to an embodiment of the invention;

[0023] Figure 13 depicts a design of a PAD according to an embodiment of the invention;

[0024] Figure 14 depicts a photograph of a headset employing a pair of PADs according to an embodiment of the invention;

[0025] Figure 15 depicts a detailed view of the constantly varying angled / beveled edge of a PAD according to an embodiment of the invention;

[0026] Figure 16 depicts a cross-section of a PAD according to an embodiment of the invention showing a silicone gasket attachment means;

[0027] Figure 17 depicts a PAD according to an embodiment of the invention depicting an offset in positioning of an attachment for a headband;

[0028] Figure 18 depicts cross-section and partial three-dimensional perspective views of a PAD employing a membrane in association with a cup according to an embodiment of the invention;

[0029] Figure 19 depicts a cross-section view of a PAD employing a membrane stack in association with a cup according to an embodiment of the invention;

[0030] Figures 20 and 21 depicts headsets employing PADs according to embodiments of the invention without and with silicone covers over shaped collars profiled to fit against the wearer’s head;

[0031] Figure 22 depicts an outer cup of a PAD according to an embodiment of the invention showing the shaped collar profiled to fit against the wearer’s head;

[0032] Figure 23 depicts a shaped collar profiled to fit against the wearer’s head forming part of an inner cup of a PAD according to an embodiment of the invention;

[0033] Figure 24 depicts acoustic spectra for a PAD according to an embodiment of the invention with and without a liner on the inner surface of the inner cup;

[0034] Figures 25 to 28 and depict alternate geometries for inner, outer, or inner and outer cups for PADs according to embodiments of the invention;

[0035] Figures 29 and 30 depict cup cross-sections of cups for PADs according to embodiments of the invention;

[0036] Figures 31 and 32 depict collar geometries according to embodiments of the invention;

[0037] Figures 33 and 34 depict perspective cross-sectional views of PADs according to embodiments of the invention;

[0038] Figures 35 and 36 depict perspective and cross-sectional views of a PAD according to embodiments of the invention; and

[0039] Figure 37 depicts the performance of a PAD according to an embodiment of the invention relative to the performance of two commercial devices;

[0040] Figure 38 depicts the performance of PAD elements and a PAD according to embodiments of the invention and a commercial noise protector;

[0041] Figure 39 depicts exemplary sealing methods exploiting skins around an outer foam element of a PAD according to an embodiment of the invention; and

[0042] Figure 40 depicts an exemplary silicone arm seal according to an embodiment of the invention.DETAILED DESCRIPTION

[0043] The present invention is directed to personal acoustic devices and more particularly to personal acoustic devices with noise blocking or noise attenuation characteristics and more particularly to designs and methods of implementing passive personal acoustic devices with noise blocking or noise attenuation characteristics discretely or with active augmentation or with additional acoustic elements.

[0044] The ensuing description provides representative embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the embodiment(s) will provide those skilled in the art with an enabling description for implementing an embodiment or embodiments of the invention. It being understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope as set forth in the appended claims. Accordingly, an embodiment is an example or implementation of the inventions and not the sole implementation. Various appearances of “one embodiment,” “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments. Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention can also be implemented in a single embodiment or any combination of embodiments.

[0045] Reference in the specification to “one embodiment”, “an embodiment”, “some embodiments” or “other embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment, but not necessarily all embodiments, of the inventions. The phraseology and terminology employed herein is not to be constmed as limiting but is for descriptive purpose only. It is to be understood that where the claims or specification refer to “a” or “an” element, such reference is not to be constmed as there being only one of that element. It is to be understood that where the specification states that a component feature, stmcture, or characteristic “may”, “might”, “can” or “could” be included, that particular component, feature, stmcture, or characteristic is not required to be included.

[0046] Reference to terms such as “left”, “right”, “top”, “bottom”, “front” and “back” are intended for use in respect to the orientation of the particular feature, stmcture, or element within the figures depicting embodiments of the invention. It would be evident that suchdirectional terminology with respect to the actual use of a device has no specific meaning as the device may be employed in a multiplicity of orientations by the user or users.

[0047] Reference to terms “including”, “comprising”, “consisting” and grammatical variants thereof do not preclude the addition of one or more components, features, steps, integers or groups thereof and that the terms are not to be construed as specifying components, features, steps or integers. Likewise, the phrase “consisting essentially of’, and grammatical variants thereof, when used herein is not to be constmed as excluding additional components, steps, features integers or groups thereof but rather that the additional features, integers, steps, components or groups thereof do not materially alter the basic and novel characteristics of the claimed composition, device or method. If the specification or claims refer to “an additional” element, that does not preclude there being more than one of the additional element.

[0048] A “fluid” as used herein refers to a liquid, a gas, a mixture of liquids or a mixture of gases.

[0049] A “wireless standard” as used herein and throughout this disclosure, refer to, but is not limited to, a standard for transmitting signals and / or data through electromagnetic radiation which may be optical, radio-frequency (RF) or microwave although typically RF wireless systems and techniques dominate. A wireless standard may be defined globally, nationally, or specific to an equipment manufacturer or set of equipment manufacturers. Dominant wireless standards at present include, but are not limited to IEEE 802.11, IEEE 802.15, IEEE 802.16, IEEE 802.20, UMTS, GSM 850, GSM 900, GSM 1800, GSM 1900, GPRS, ITU-R 5.138, ITU-R 5.150, ITU-R 5.280, IMT-1000, Bluetooth, Wi-Fi, Ultra-Wideband and WiMAX. Some standards may be a conglomeration of sub-standards such as IEEE 802.11 which may refer to, but is not limited to, IEEE 802.1a, IEEE 802.11b, IEEE 802.11g, or IEEE 802.1 In as well as others under the IEEE 802.11 umbrella.

[0050] A “wired standard” as used herein and throughout this disclosure, generally refer to, but is not limited to, a standard for transmitting signals and / or data through an electrical cable discretely or in combination with another signal. Such wired standards may include, but are not limited to, digital subscriber loop (DSL), Dial-Up (exploiting the public switched telephone network (PSTN) to establish a connection to an Internet service provider (ISP)), Data Over Cable Service Interface Specification (DOCSIS), Ethernet, Gigabit home networking (G.hn), Integrated Services Digital Network (ISDN), Multimedia over Coax Alliance (MoCA), and Power Line Communication (PLC, wherein data is overlaid to AC / DC power supply). In some embodiments a “wired standard” may refer to, but is not limited to, exploiting an optical cable and optical interfaces such as within Passive Optical Networks (PONs) for example.

[0051] A “sensor” as used herein may refer to, but is not limited to, a transducer providing an electrical output generated in dependence upon a magnitude of a measure and selected from the group comprising, but is not limited to, environmental sensors, medical sensors, biological sensors, chemical sensors, ambient environment sensors, position sensors, motion sensors, thermal sensors, infrared sensors, visible sensors, RFID sensors, and medical testing and diagnosis devices.

[0052] A “portable electronic device” (PED) as used herein and throughout this disclosure, refers to a wireless device used for communications and other applications that requires a battery or other independent form of energy for power. This includes devices, but is not limited to, such as a cellular telephone, smartphone, personal digital assistant (PDA), portable computer, pager, portable multimedia player, portable gaming console, laptop computer, tablet computer, a wearable device and an electronic reader.

[0053] A “fixed electronic device” (FED) as used herein and throughout this disclosure, refers to a wireless and / or wired device used for communications and other applications that requires connection to a fixed interface to obtain power. This includes, but is not limited to, a laptop computer, a personal computer, a computer server, a kiosk, a gaming console, a digital set-top box, an analog set-top box, an Internet enabled appliance, an Internet enabled television, and a multimedia player.

[0054] A “user” as used herein may refer to, but is not limited to, an individual or group of individuals. This includes, but is not limited to, private individuals, employees of organizations and / or enterprises, members of community organizations, members of charity organizations, men and women. In its broadest sense the user may further include, but not be limited to, software systems, mechanical systems, robotic systems, android systems, etc. that may be characterised by an ability to exploit one or more embodiments of the invention.

[0055] A “polymer” as used herein may refer to, but is not limited to, is a large molecule, or macromolecule, composed of many repeated subunits. Such polymers may be natural and synthetic and typically created via polymerization of multiple monomers. Polymers through their large molecular mass may provide unique physical properties, including toughness, viscoelasticity, and a tendency to form glasses and semi-crystalline structures rather than crystals.

[0056] A “polyester” as used herein, and throughout this disclosure, refers to a category of polymers that contain the ester functional group in their main chain. This includes, but is not limited to polyesters which are naturally occurring chemicals as well as synthetics through step-growth polymerization, for example. Polyesters may be biodegradable or not. Polyestersmay be a thermoplastic or thermoset or resins cured by hardeners. Polyesters may be aliphatic, semi-aromatic or aromatic. Polyesters may include, but not be limited to, those exploiting polyglycolide, polylactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polyethylene adipate (PEA), polybutylene succinate (PBS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), and polyethylene naphthalate (PEN).

[0057] A “thermoplastic” or “thermosoftening plastic” as used herein and throughout this disclosure, refers to a category of polymers that become pliable or moldable above a specific temperature and solidify upon cooling. Thermoplastics may include, but not be limited, polycarbonate (PC), polyether sulfone (PES), polyether ether ketone (PEEK), polyethylene (PE), polypropylene (PP), poly vinyl chloride (PVC), polytetrafluoroethylene (PTFE), polyimide (PI), polyphenylsulfone (PPSU), polychlorotrifluoroethene (PCTFE or PTFCE), fluorinated ethylene propylene (FEP), acrylonitrile butadiene styrene (ABS) and perfluoro alkoxy alkane (PFA).

[0058] An “aramid” as used herein, and throughout this disclosure, refers to an aromatic polyamide. Aramids are a class of materials fibers in which the chain molecules are highly oriented along the fiber axis, so the strength of the chemical bond may be exploited. Examples include, but are not limited to fibers distributed under brand names such as Kevlar™, Technora™, Twaron™, Heracron™, Nomex™, Innegra S™ and Vectran™ as well as nylon and ultra-high molecular weight polyethylene.

[0059] A “silicone” as used herein, and throughout this disclosure, refers to a polymer that includes any inert, synthetic compound made up of repeating units of siloxane.

[0060] An “elastomeric” material or “elastomer” as used herein, and throughout this disclosure, refers to a material, generally a polymer, with viscoelasticity. Elastomers may include, but not be limited to, unsaturated rubbers such as polyisoprene, butyl rubber, ethylene propylene rubber, silicone rubber, fluorosilicone rubber, fluoroelastomers, perfluoroelastomers, and thermoplastic elastomers.

[0061] The term “flexible,” as used herein, refers to the ability of a body that is capable of being bent or flexed and refers to the ability of a body that has been subjected to an external force to return to its original size and / or shape once the external force has been removed or reduced to below a particular level. Something that is flexible may be, for example, resilient or malleable. A “flexible” material, such as a rubber for example, may be characterised by a low Young’s modulus.

[0062] The term “resilient,” as used herein, refers to the ability of a body that has been subjected to an external force to recover, or substantially recover, its original size and / or shape, following deformation. The term “malleable,” as used herein, refers to the ability of a body that has been subjected to an external force to deform and maintain, or substantially maintain, the deformed size and / or shape. Accordingly, a malleable material supports plastic deformation. A resilient material, such as polytetrafluorethylene for example, may be characterised by a moderate Young’s modulus. A rigid material, for example steel, may be characterised by a high Young’s modulus but may under appropriate conditions undergo plastic deformation.

[0063] A “personal acoustic device” (PAD) as used herein, and throughout this disclosure, refers to a device which fits into, on or over an ear of a user in order to attenuate the propagating of acoustic signals in the external environment to the user’s ear. A PAD may be a passive device and provide functionality similar to that of ear protectors or ear defenders or it may incorporate active elements such as a loudspeaker or loudspeakers, active noise cancelling etc. and provide functionality similar to that of over-the-ear or on-ear headphones or in-the-ear earphones (also known as earbuds). A PAD may provide passive PAD functionality until powered on wherein it may provide active PAD functionality to augment or complement its passive PAD functionality.

[0064] A “cup” as used herein, and throughout this disclosure, refers to a three-dimensional object with a defined geometry which has an opening and encloses a region. An “inner cup” as used herein, and throughout this disclosure, refers to a cup which is disposed within another cup. An “outer cup” as used herein, and throughout this disclosure, refers to a cup which is disposed externally to one or more other cups such that the outer cup is the outermost cup of the two or more cups. A “set of cups” as used herein, and throughout this disclosure, refers to an outer cup within which are disposed one or more inner cups.

[0065] A “collar” as used herein, and throughout this disclosure, refers to a region of a cup that extends towards the body of the user from a body of the cup.

[0066] A “wall” or “sound barrier” as used herein, and throughout this disclosure, refers to a surface or surfaces disposed within a path of an acoustic signal, e.g. from the external environment towards an ear of a personal acoustic device wearer according to embodiments of the invention. Accordingly, each of the inner cup and the outer cup form walls of a personal acoustic device according to an embodiment of the invention. A wall may be formed from a single layer of a material or it may be formed from multiple layers of a material such as in a laminate.

[0067] A “stiffness driven wall” as used herein, and throughout this disclosure, refers to a wall where a frequency or frequencies of interest of acoustic signals impinging upon the wall is within a stiffness region of the wall. This region of a wall is described and depicted in Figure 3.

[0068] A “mass driven wall” as used herein, and throughout this disclosure, refers to a wall where a frequency or frequencies of interest of acoustic signals impinging upon the wall is within the mass region of the wall. This region of a wall is described and depicted in Figure 3.

[0069] Referring to Figure 1 there is depicted a Portable Electronic Device (Portable Device) 104 and network access point 107 supporting AIAL-SAP features according to embodiments of the invention. Portable Device 104 may include additional elements beyond those described and depicted or it may comprise a subset of the elements described. Also depicted within the Portable Device 104 is a protocol architecture as part of a simplified functional diagram of a System 100 that includes a Portable Device 104, an Access Point (AP) 106 and one or more Network Devices 107, such as communication servers, streaming media servers, and routers for example such as first to third Servers 190A to 190C respectively. Network Devices 107 may be coupled to AP 106 via any combination of networks, wired, wireless and / or optical communication links. Network Devices 107 are coupled to Network 100 and therein Social Networks (SOCNETS) 165, first and second Service Providers 170A and 170B respectively, first and second Third Party Service Providers 170C and 170D respectively, a User 170E, first and second Enterprises 175A and 175B respectively, first and second Organizations 175C and 175D respectively, and a Government Entity 175E.

[0070] The Portable Device 104 includes one or more processors 110 and a memory 112 coupled to processor(s) 110. AP 106 also includes one or more processors 111 and a memory 113 coupled to processor(s) 110. A non-exhaustive list of examples for any of processors 110 and 111 includes a central processing unit (CPU), a digital signal processor (DSP), a reduced instruction set computer (RISC), a complex instruction set computer (CISC) and the like. Furthermore, any of processors 110 and 111 may be part of application specific integrated circuits (ASICs) or may be a part of application specific standard products (ASSPs). A non-exhaustive list of examples for memories 112 and 113 includes any combination of the following semiconductor devices such as registers, latches, ROM, EEPROM, flash memory devices, non-volatile random access memory devices (NVRAM), SDRAM, DRAM, double data rate (DDR) memory devices, SRAM, universal serial bus (USB) removable memory, and the like.

[0071] Portable Device 104 may include an audio input element 114, for example a microphone, and an audio output element 116, for example, a speaker, coupled to any of processors 110. Portable Device 104 may include a video input element 118, for example, a video camera or camera, and a video output element 120, for example an LCD display, coupled to any of processors 110. Portable Device 104 also includes a keyboard 115 and touchpad 117 which may for example be a physical keyboard and touchpad allowing the user to enter content or select functions within one of more applications 122. Alternatively, the keyboard 115 and touchpad 117 may be predetermined regions of a touch sensitive element forming part of the display within the Portable Device 104. The one or more applications 122 that are typically stored in memory 112 and are executable by any combination of processors 110. Portable Device 104 also includes accelerometer 160 providing three-dimensional motion input to the process 110 and GPS 162 which provides geographical location information to processor 110.

[0072] Portable Device 104 includes a protocol stack 124 and AP 106 includes a communication stack 125. Within system 100 protocol stack 124 is shown as IEEE 802.11 protocol stack but alternatively may exploit other protocol stacks such as an Internet Engineering Task Force (IETF) multimedia protocol stack for example. Likewise, AP stack 125 exploits a protocol stack but is not expanded for clarity. Elements of protocol stack 124 and AP stack 125 may be implemented in any combination of software, firmware and / or hardware. Protocol stack 124 includes an IEEE 802.11 -compatible PHY module 126 that is coupled to one or more Front-End Tx / Rx & Antenna 128, an IEEE 802.11 -compatible MAC module 130 coupled to an IEEE 802.2-compatible LLC module 132. Protocol stack 124 includes a network layer IP module 134, a transport layer User Datagram Protocol (UDP) module 136 and a transport layer Transmission Control Protocol (TCP) module 138.

[0073] Protocol stack 124 also includes a session layer Real Time Transport Protocol (RTP) module 140, a Session Announcement Protocol (SAP) module 142, a Session Initiation Protocol (SIP) module 144 and a Real Time Streaming Protocol (RTSP) module 146. Protocol stack 124 includes a presentation layer media negotiation module 148, a call control module 150, one or more audio codecs 152 and one or more video codecs 154. Applications 122 may be able to create maintain and / or terminate communication sessions with any of devices 107 by way of AP 106. Typically, applications 122 may activate any of the SAP, SIP, RTSP, media negotiation and call control modules for that purpose. Typically, information may propagate from the SAP, SIP, RTSP, media negotiation and call control modules to PHY module 126 through TCP module 138, IP module 134, LLC module 132 and MAC module 130.

[0074] It would be apparent to one skilled in the art that elements of the Portable Device 104 may also be implemented within the AP 106 including but not limited to one or more elements of the protocol stack 124, including for example an IEEE 802.11 -compatible PHY module, an IEEE 802.11 -compatible MAC module, and an IEEE 802.2-compatible LLC module 132. The AP 106 may additionally include a network layer IP module, a transport layer User Datagram Protocol (UDP) module and a transport layer Transmission Control Protocol (TCP) module as well as a session layer Real Time Transport Protocol (RTP) module, a Session Announcement Protocol (SAP) module, a Session Initiation Protocol (SIP) module and a Real Time Streaming Protocol (RTSP) module, media negotiation module, and a call control module. Portable and fixed electronic devices represented by Portable Device 104 may include one or more additional wireless or wired interfaces in addition to the depicted IEEE 802.11 interface which may be selected from the group comprising IEEE 802.15, IEEE 802.16, IEEE 802.20, UMTS, GSM 850, GSM 900, GSM 1800, GSM 1900, GPRS, ITU-R 5.138, ITU-R 5.150, ITU-R 5.280, IMT-1000, DSL, Dial-Up, DOCSIS, Ethernet, G.hn, ISDN, MoCA, PON, and Power line communication (PLC).

[0075] Also depicted in Figure 1 are Electronic Devices (EDs) 1000 according to embodiments of the invention such as described and depicted below in respect of Figures 2 to XXX or other PEDs and / or FEDs as known in the art. As depicted in Figure 1 an ED 1000 may communicate directly to the Network 100 whilst other EDs 1000 may communicate to the Network 100 via the Network Device 107, Access Point 106, and Portable Device 104. Some EDs 1000 may communicate with other EDs 1000 directly and some EDs 1000 may only communicate with the Portable Device 104. Within Figure 1 the EDs 1000 coupled to the Network 100 and Network Device 107 communicate via wired interfaces. The EDs 1000 coupled with the Access Point 106 and Portable Device 104 communicate via wireless interfaces. Each ED 1000 may communicate to another electronic device, e.g. Access Point 106, Portable Device 104 and Network Device 107, or a network, e.g. Network 100. Each ED 1000 may support one or more wireless or wired interfaces including those, for example, selected from the group comprising IEEE 802.11, IEEE 802.15, IEEE 802.16, IEEE 802.20, UMTS, GSM 850, GSM 900, GSM 1800, GSM 1900, GPRS, ITU-R 5.138, ITU-R 5.150, ITU-R 5.280, IMT-1000, DSL, Dial-Up, DOCSIS, Ethernet, G.hn, ISDN, MoCA, PON, and Power line communication (PLC).

[0076] Accordingly, Figure 1 depicts an Portable Device 104, e.g. a PED, wherein one or more parties including, but not limited to, a user, users, an enterprise, enterprises, third party provider, third party providers, wares provider, wares providers, financial registry, financialregistries, financial provider, and financial providers may engage in one or more financial transactions relating to an activity including, but not limited to, e-business, peer to peer (P2P), consumer to business (C2B), business to business (B2B), consumer to consumer (C2C), business to Government (B2G), consumer to government (C2G), physical to digital (P2D), and digital to digital (D2D) activities via the Network 100 using the electronic device or within either the AP 106 or Network Device 107 wherein details of the transaction are then coupled to / from the Network 100 and stored within / retrieved from remote servers or other data sources.

[0077] Optionally, rather than wired and. / or wireless communication interfaces devices may exploit other communication interfaces such as optical communication interfaces and / or satellite communications interfaces. Optical communications interfaces may support Ethernet, Gigabit Ethernet, SONET, Synchronous Digital Hierarchy (SDH) etc. Accordingly, the first and second user groups 100A and 100B may, according to their particular communications interfaces communicate to the Network 100 through one or more wireless communications standards such as, for example, IEEE 802.11, IEEE 802.15, IEEE 802.16, IEEE 802.20, UMTS, GSM 850, GSM 900, GSM 1800, GSM 1900, GPRS, ITU-R 5.138, ITU-R 5.150, ITU-R 5.280, and IMT-1000. It would be evident to one skilled in the art that many portable and fixed electronic devices may support multiple wireless protocols simultaneously, such that for example a user may employ GSM services such as telephony and SMS and Wi-Fi / WiMAX data transmission, VOIP and Internet access. Accordingly, a Portable Device 104 may form associations either Eds 1000, AP 106m, Network Device 107 or other Portable Devices 104 through standards such as IEEE 802.15 and Bluetooth as well in an ad-hoc manner using one or more wired and / or wireless communication formats.

[0078] Accordingly, it would be beneficial to provide users with improved passive acoustic attenuation which provides superior hearing protection for high noise environments (e.g. factories, construction sites, airports, concerts, shooting ranges, military contexts, racetracks etc.). Passive systems offer limited ways to fail while active systems are complex and can fail unexpectedly. Accordingly, passive acoustic attenuation provides standalone devices which do not require electricity or any infrastructure and can block sound non-stop without interruption.

[0079] Additionally, improved passive acoustic attenuation devices can also provide users with means for enhanced concentration for working or studying, especially in distraction heavy environments (e.g. cubicles, trading floors, coffee shops etc.) as well as superior sound isolation to avoid human sleep disturbances etc.

[0080] Accordingly, it would be beneficial to provide users with improved passive acoustic attenuation which provides superior hearing protection for high noise environments (e.g.factories, construction sites, airports, concerts, shooting ranges, military contexts, racetracks etc.). Passive systems offer limited ways to fail while active systems are complex and can fail unexpectedly. Accordingly, passive acoustic attenuation provides standalone devices which do not require electricity or any infrastructure and can block sound non-stop without interruption. As such the improved passive acoustic attenuation devices can also provide users with means for enhanced concentration for working or studying, especially in distraction heavy environments (e.g. cubicles, trading floors, coffee shops etc.) as well as superior sound isolation to avoid human sleep disturbances etc.

[0081] Whilst the following description is made with respect to the full spectrum of human hearing, which is generally considered to range from approximately 20 Hz to approximately 20 kHz, it would be evident that the concepts, principles and designs presented below may be applied to either providing an aural device for use by a human user over or outside a portion of the human spectrum of hearing or they may be applied to providing hearing aural devices for non-human users over frequency ranges which may overlap with a portion of the human hearing range or may extend to higher frequencies or lower frequencies or not overlap the human hearing spectrum at all.

[0082] Within the following description the design of the personal acoustic devices has been driven by a number of constraints, there being mass (or weight), form (or ergonomic), aesthetic and economical constraints. However, it would be evident that the concepts, principles and designs presented below may be applied to provide personal acoustic devices to users with different constraints in terms of mass, aesthetics and economics or may have fewer constraints or other additional constraints.

[0083] With respect to the mass constraint the overall headset, which may be for a pair of personal acoustic devices (PADs), as referred to by the inventor where a PAD fits into, on or over the ear of the user with associated head support / mounting should not exceed a defined total mass, otherwise it will be uncomfortable for the user to wear. Optionally, the mass of the PAD may be defined in dependence upon an aspect of the user or an aspect of the mounting of the PAD(s). For example, the mass of a PAD being supported by a band across the top of the user’s head may be higher than that for a PAD which is being supported by a support around the back of the user’s head. This is referred to as the “mass budget.” With respect to the aesthetic constraint the overall headset has been considered as having a similar aesthetic look as a conventional pair of headphones or ear protectors for example so that the user does not feel self-conscious or embarrassed to wear them around others. Accordingly, the PADs and overall headset may not be too large or irregularly shaped etc. although embodiments of theinvention may be for deliberate aesthetic differentiation for example. This is referred to as the “form constraint.” With respect to the economic constraint the headset should be compatible with low cost manufacturing so that it may be sold at a price that is accessible to the mass market. This is referred to as the “economical budget.”

[0084] Referring to Figure 2 there is depicted a frequency spectrum of “normal” human hearing which extends from approximately 20 Hz to approximately 20 kHz which can comprise sub-regions which are typically defined as:• Bass: approximately 20 Hz to approximately 150 Hz• Upper Bass: approximately 150 Hz to approximately 300 kHz • Mid-Range: approximately 300 Hz to approximately 2.5 kHz • Upper Mid-Range: approximately 2.5 kHz to approximately 5 kHz• High End: approximately 5 kHz to approximately 20 kHz

[0085] Below 20 Hz acoustic signals are referred to as sub-sonic and above 20 kHz as supersonic.

[0086] As a sound wave (sound) travels from one medium to another, some of the sound is transmitted and the rest of the sound is reflected where the greater the difference in specific acoustic impedance between the two mediums (specific acoustic impedance of a medium being defined as the density of a medium in kg / m3multiplied by the speed of sound in the medium in m / s), the more sound is reflected. Equation (1) below describes the relationship between the specific acoustic impedances of two sequential media and the resulting fraction of incident wave energy that is reflected where R is the reflection coefficient (fraction of the incident wave intensity that is reflected, unitless), Z1 is the specific acoustic impedance of the medium (Medium 1) within which the sound is initially traveling and Z2 is the specific acoustic impedance of the other medium (Medium 2) the sound will travel in once it crosses the boundary between Medium 1 and Medium 2.

[0087] R=0 would mean that all of the sound was transmitted with no reflection whilst R=1 would mean that all of the sound was reflected with no transmission. In the context of a sound attenuating headset, the objective is to achieve the greatest reflection possible for the sound propagating from the surrounding environment to the user’s ear and therein the sound reaching the ear canal / ear drum etc. which means that a design goal for a PAD providing high quality sound isolation for the user would target achieving a high R value, the closer to 1 the better.

[0088] The sound we wish to reflect (or otherwise block from reaching the user’s ear) starts out in the surrounding air which has a generally speaking low specific acoustic impedance value (Zl) and may be considered a constant, although it will vary slightly with pressure, altitude, temperature and humidity. To achieve a high degree of reflection, mathematically we would desire this sound to be met with a second medium (a portion of the headset) that has a different specific acoustic impedance value (either an extremely low or extremely high value for Z2). In practice a greater specific acoustic impedance mismatch may be established while trying to maximize rather than minimize the value of Z2. This is because there are very few materials that have a specific acoustic impedance value less than that of air. However, the design concepts presented here can support a PAD formed from a material with a low specific acoustic impedance.

[0089] Whilst the designs are described and presented with respect to the PADs and associated headset being upon a user’s head within air it would be evident that within other embodiments of the invention the surrounding fluid may be a fluid other than air, such as water for example. Accordingly, the specific acoustic impedance Zl changes and a different value for Z2 will be required to achieve the same R value at any given medium change interface.

[0090] Osmium, iridium, tungsten, and rhenium are among the materials with the highest specific acoustic impedance values on Earth being roughly between 98,000,000 and 130,000,000 kg / s / m2relative to that of dry air at atmospheric pressure and 25 °C which is considered to be 385 kg / s / m2. Within this specification the inventor employs kg / s / m2rather than the rayl which is the unit of specific acoustic impedance where 1 rayl = 1 kg / s / m2. However, constructing a PAD for a headset shell out of a solid piece of one of these materials may be prohibitively expensive due to a combination of raw material costs and processing costs. However, that does not preclude such embodiments within the scope of the invention as other cost points of PADs may be acceptable to some users and ongoing developments in manufacturing, such as three-dimensional (3D) printing with tungsten and tungsten carbide for example is progressing such that it may be economical to make the cups out of an extremely high specific acoustic impedance material like tungsten or tungsten carbide. The inventor also notes that 3D printing of stainless steel is now feasible as a manufacturing methodology for PADs according to embodiments of the invention.

[0091] In contrast, iron, steel, and stainless steel have the highest specific acoustic impedance values among common manufacturing materials at roughly 46,000,000 kg / s / m2. Although all three of these options have similar specific acoustic impedance values the inventor below describes and depicts PAD designs employing stainless steel as it does not requireadditional processing or surface treatments to provide corrosion resistance allowing the outer cup of the PAD to maintain external visible surfaces which may be aesthetically pleasing to users and help reduce manufacturing costs. However, it would be evident that iron, steel and varying grades of stainless steel may be employed without departing from the level of corrosion resistance required with surface treatments, coatings, coverings etc.

[0092] Optionally, within embodiments of the invention a cup may be formed with one or more coatings employing one or more high specific acoustic impedance materials which are formed through methods as known in the art. For example, tungsten could be coated to an internal and / or external surface of a cup formed from a material with a lower specific acoustic impedance. This may, for example, be via spray coating, vapor deposition, plating etc. It would be evident in Equation (1) that the R value does not depend on the thickness of a medium and accordingly a design with a coating of a high specific acoustic impedance material upon a material with lower specific acoustic impedance allows for improved performance at a different cost point compared to a design solely employing the high specific acoustic impedance material.

[0093] Since stainless steel has a high specific acoustic impedance value among economical building materials and has the added benefit of having good corrosion resistance at standard indoor temperatures and humidities, it may be concluded that stainless steel may be used as a material for the prototype headsets developed by the inventor. For cross-reference the specific acoustic impedances of acrylonitrile butadiene styrene (ABS), polycarbonate, nylon, polyethylene and polyvinyl chloride (PVC) are approximately 2,400,000 kg / s / m2, 2,800,000 kg / s / m2, 3,150,000 kg / s / m2, 2,350,000 kg / s / m2and 3,250,000 kg / s / m2respectively. These are common plastics employed in prior art passive ear defenders and accordingly are less than approximately 7.5 % of the specific acoustic impedance of stainless steel.

[0094] Impedance matching is well known in the electronic circuit design industry and can also apply to acoustics. With impedance matching the transmitted acoustic signal increases, i.e. a reduction in the sound transmission loss (STL) by introducing a gradual transition from one (e.g. low) specific acoustic impedance to another (e.g. high) specific acoustic impedance. In the context of a sound attenuating headset, this means that adding a material with a specific acoustic impedance between that of stainless steel and air (e.g., paint, powder coating, etc.) between these two mediums is generally inadvisable and may even be detrimental to the STL as the other material or materials are more than likely to have a specific acoustic impedance value between that of air and stainless steel and act as an impedance matching layer to reduce the STL. For example, iron oxide on an iron body of a PAD will have a different specificacoustic impedance value than iron and therefore could possibly produce a noticeable decrease in STL performance. However, other factors such as aesthetics may impact this decision. For example, within this context a layer of corrosion may be detrimental from the performance perspective as well as from an aesthetic viewpoint such that a protective coating with defined characteristics is preferred to the performance and visual degradations from corrosion. A coating may also be employed for improved aesthetic reasons (e.g. a different colour) despite the impedance matching risk to STL performance.

[0095] Referring to Figure 3 there is depicted a Plot 300A of sound transmission loss (STL) versus frequency for a generic sound barrier and Inset 300B which depicts a simplified STL versus frequency plot. These being for a generic solid and non-porous wall / sound barrier where the vertical axis is STL in dB and the horizontal axis is the frequency of sound in Hz. Within the following description of PADs then the designs described and depicted are for the full spectrum of human hearing, namely from approximately 20 Hz to approximately 20 kHz, although it would be evident that the concepts presented may be adjusted for sub-ranges of the full spectrum, e.g. the bass or upper bass ranges or the mid-range and upper mid-range. However, it would also be evident that the concepts presented may also be adjusted for ranges outside of the normal hearing range of a human.

[0096] As depicted the Plot 300A comprises a series of regions identified as Stiffness Region 300C, Resonance Region 300D, Mass Region 300E and Coincidence Region 300F. Within Mass Region 300E as with a greater specific acoustic impedance mismatch, increasing mass can improve sound attenuation performance. Accordingly, if we consider the wall as a single solid object, it makes intuitive sense that higher total wall mass means greater inertia, and therefore a higher resistance to being set into motion by a given sound wave. A wall with greater mass will therefore have greater STL in the mass region. It is further evident from Mass Region 300E in Plot 300A that sound waves with increasing frequency experience higher STL, while lower sound wave frequencies experience lower STL.

[0097] Within the Resonance Region 300D in Plot 300A then if the sound wave in question has a frequency that is equal to or close to a wall's resonant frequency (or a positive multiple thereof), it follows that the wall can get greatly excited and have a lower STL than the mass law would predict (the mass law will be described by Equation (3) later on in this document). This behavior is captured by the multiple dips in the Resonance Region 300D associated with multiple resonant frequencies which start at the 1stResonant Frequency 320. The dotted line represents the Mass Law Extension 310 and accordingly in the Resonance Region 300D the curve dips below and goes above this line. The Resonance Region 300D is where the poorestsound attenuating performance is generally observed as the barrier is resonating in this region. The addition of a damping material will help transform the kinetic energy (movement) of the wall into heat and therefore move the STL to be closer to what the mass law would predict. An example of damping in this context is installing a thick mastic / tar-like substance to a side of the wall. The addition of a damping substance causes more sound wave energy to get absorbed in the resonance region. For example, a damping substance may include a natural rubber, a silicone of defined durometer, a synthetic rubber, an elastomeric material, a foam, a plastic, a mass loaded vinyl, an elastomer or a viscoelastic polymer for example.

[0098] Within the Coincidence Region 300F, similar to portions of the Resonance Region 300D , the STL values observed are lower than the Mass Law Extension 310 would predict. In this case, rather than modes of the wall's resonant frequencies being the cause of lower STL values, it is due to the interaction between the wavelength of the sound wave and the wavelength of the bending waves of the wall. When these wavelengths are equal this causes high transmission and the STL dip evident within the Coincidence Region 300F that has its minimum at the Critical Frequency 330. Frequencies around the Critical Frequency 330 attenuate less than the mass law would predict although more than at the critical frequency as the wavelength of the sound wave and the wavelength of the bending waves of the wall increasingly differ. The addition of a damping material can also increase sound wave energy absorption in this region.

[0099] Within the Coincidence Region 300F there is the Critical Frequency 330 which may be estimated using Equation (2) where fcis the critical frequency , A is the critical frequency constant for a medium (Hz- mm) and t is the wall thickness (mm). For example, a 1.2mm (0.047”) thick wall of steel (A = 12,700 Hz- mm) will have a critical frequency of approximately 10,583 Hz. In this case, the STL effects of coincidence are unlikely to be seen in approximately the first half of the human hearing range. By changing the material used and the wall thickness you can adjust the critical frequency to be higher or lower than this. This is one way that a designer can adjust the STL at various frequency ranges. For example, the critical frequency could be placed in the human speech frequency range so that voices are heard more easily.fc = (2)

[0100] In the context of a STL-frequency plot, the Stiffness Region 300C covers sound frequencies below the 1stResonant Frequency 320, and therefore sound waves with larger wavelengths, where the effect of the sound wave on the wall begins to approximate that of a static pressure wherein the less the wall flexes due to its stiffness, the less the air molecules onthe other side of the wall are set into motion, resulting in increased STL. Accordingly, in the Stiffness Region 300C a greater stiffness results in higher STL values and a greater total mass does not have as much of an effect.

[0101] Inset 300B in Figure 3 depicts a generic curve from Plot 300A of Figure 3 and assumes no resonance or coincidence effects and has the shape of a “V” with increasing STL values on either side of the first resonant frequency, f2. If a frequency of interest,is below the first resonant frequency f2then the STL is driven by stiffness and so the inventor refers to this as a “Stiffness Driven Wall”. If the frequency of interest,3, is above the first resonant frequency f2then the STL is driven by mass and so the inventor refers to this as a “Mass Driven Wall”.

[0102] Accordingly, as STL values are higher with lower frequencies in the stiffness region, regardless of whether the frequency of interest is above or below the resonant frequency the corresponding STL may be improved by raising the resonant frequency. The result is that the frequency of interest resides in the stiffness region. As depicted in first Plot 400A in Figure 4, increasing the resonant frequency from410to430results in the STL value at the frequency of interest / 42o increasing from its original STL value 470A to the Stiffness Driven Wall STL value 470B. Similarly, as depicted in second Plot 400B in Figure 4, if the original first resonant frequency / 430is above the frequency interest440then increasing the first resonant frequency to the increased first resonant frequency460similarly results in the STL value being increased from its original value 480A to the increased Stiffness Driven Wall STL value 480B.

[0103] In contrast, referring to Figure 5 in first Plot 500A when reducing the first resonant frequency from its initial value f520which is below the frequency of interest f530to a lower first resonant frequency510then the STL value does not increase between its original STL value 570A and the Mass Driven Wall STL value 570B. In the second Plot 500B where the frequency of interest f550is below the initial resonant frequency560then reducing the resonant frequency to f54Oresults in the STL value being shifted from its original STL value 580A to a lower Mass Driven Wall STL value 580B. So, in either scenario, lowering the first resonant frequency offers no STL advantage in this simplified analysis that sets aside resonance and coincidence effects. Thus, regardless if a frequency of interest is above or below the resonant frequency the corresponding STL may be improved by raising the resonant frequency. Accordingly, a Stiffness Driven Wall may be employed over a Mass Driven Wall, although Mass Driven Walls may be used within embodiments of the invention.

[0104] If a Mass Driven Wall was to be employed then its STL value may be improved by increasing the mass of the wall as much as possible while making the first resonant frequency as low as possible. The latter results in the greatest range of frequencies being subject to an increase in STL due to the increased mass of the wall. This being depicted in Figure 6 where the frequency of interest630is above the initial resonant frequency620then increasing the mass and lowering the first resonant frequency to610the STL increases from its original value 640A to an increased STL value 640B with the increased mass of the Mass Driven Wall. In this case, lowering the first resonant frequency did not increase STL at the frequency of interest but it did increase the range of frequencies being subject to an increase in the STL value due to the increased mass of the wall.

[0105] Stiffness Driven Walls: In designing a sound barrier that has its performance driven by stiffness, the wall should have a high first resonant frequency so that all or a significant portion of the frequency range of interest is below the resonant frequency and hence in the Stiffness Region 300C in Plot 300A in Figure 3. In order to increase the first resonant frequency of a solid wall, you can increase its stiffness or decrease its mass. To maximize the first resonant frequency, the objective is to make the wall as stiff as possible per unit of mass. Examples of how to achieve this include geometry, wall thickness and material selection.

[0106] Certain geometries lend themselves to higher stiffness given the same total mass. Bridge design is a testament to how very high stiffness may be achieved with limited materials (mass) through the use of an intelligent geometry. Additional mechanical features such as ribs, braces, stiffeners, and gussets can increase the stiffness of a given shape. A shape with high stiffness per unit of mass for forces that come from any direction like sound does is the sphere because it uniformly distributes the stresses from these forces across its surface. Accordingly, the inventor has based prototype designs upon mimicking a sphere's geometry as much as possible for a high stiffness. With respect to wall thickness it is known that a cantilevered beam which is taller is one that is more resistant to bending (higher stiffness) than a thinner beam. In fact, for a beam with a constant rectangular shaped cross section, the stiffness goes by the cube of the height, so a doubling in beam height results in an eightfold increase in stiffness. Similarly, for a given wall geometry a higher wall thickness will result in higher stiffness. However, in practice significant measurable improvements in STL are only found up to a certain wall thickness / stiffness. For example, for a 115mm / 4.5” outer diameter hemispherical outer cup the Applicant has measured increased STL as the wall thickness was increased from 0.6mm and 0.8mm to 1.0mm (0.023” and 0.031” to 0.039”) but did not measure further significant increases in STL with 1.2mm and 1.5mm (0.047” and 0.060”) wall thicknesses.Accordingly, given the mass budget it may make sense to employ a wall thickness that is sufficient, but not unnecessarily high.

[0107] With respect to material selection, it is known that certain materials are inherently stiffer than others. The Young’ s modulus value of a material is the ratio of tensile stress divided by strain (deformation) in the elastic (linear) region of the stress-strain curve, and is a common property for quantifying the stiffness of materials. More relevant in this context is a material's specific Young’s modulus, which is the Young’s modulus value divided by the material's density. A wall made of a material with a greater specific Young’s modulus is one that provides increased stiffness for a given total mass allocation assuming the same geometry. Therefore, within embodiments of the invention the PADs may utilize a material or materials with high specific Young’s modulus. The addition of a reinforcement material such as glass fibers, aramid fibers, metal fibers within a thermoplastic, for example, in order to increase the material’s stiffness without significant weight. Whilst diamond and some ceramics such as alumina have extremely high specific Young’s modulus values these would be expensive materials both per se and via the more expensive manufacturing methods required. However, amongst common materials, iron, steel, and stainless steel have similar and high specific Young’s modulus values. Accordingly, based upon these considerations and those outlined above stainless steel with its high specific Young’ s modulus value provides a suitable candidate material for a stiffness driven wall of a PAD according to an embodiment of the invention.

[0108] Mass Driven Walls: In designing a sound barrier that has its performance driven by mass then the wall should have a low first resonant frequency so that all or a significant portion of the frequency range of interest is above the first resonant frequency and hence in the Mass Region 300E of Plot 300A in Figure 3. In order to decrease the first resonant frequency of a solid wall typical techniques are to decrease its stiffness and / or increase its mass. Accordingly, the design goal for a mass driven wall is to minimize the magnitude of the first resonant frequency by making the wall as “limp” or low stiffness as possible with the most mass possible while staying within the mass budget. One example of how to achieve this is what the inventor refers to as compositing.

[0109] Compositing can achieve low stiffness by using a high density powder as the filler within a “limp” matrix material such as silicone or an elastomer for example. In this case a silicone matrix or elastomer matrix greatly decreases the stiffness of the wall whilst the powder serves to increase the density of the wall. Of course one could achieve the same wall mass by simply using a thicker silicone or elastomer wall, but this would take up more space. If a high density filler is used within the silicone or elastomer for example, the same mass per unit areamay be achieved with a lower wall thickness. Thus it is possible to increase STL using a Mass Driven Wall, however the theory discussed in the 00122 and 00123 sections suggests that a Stiffness Driven Wall may also be employed. Therefore, the concept of a Mass Driven Wall can optionally be used, and compositing is a method that could be employed to provide a Mass Driven Wall instead of or in addition to one or more Stiffness Driven Walls.

[0110] The inventor uses the term multiplicity to refer to the phenomenon that having more than one of something may be useful. For example, having more batteries in series can provide more voltage to a lightbulb in an electric circuit. With respect to multiplicity it was noted above in the discussion on transmission loss regions of a wall / sound barrier that within the mass region, Mass Region 300E in Figure 3, higher frequencies experience greater STL than lower frequencies. The Mass Law in Equation (3) describes this relationship more formally where RS is the reduction in sound level transmitted in dB, f is the frequency of the sound wave in Hz and m is the mass per unit area of the wall in kg / m2. The inventor notes that Equation (3) is only valid within the mass region, e.g. Mass Region 300E in Figure 3.RS = 20log f * ni) — 48 (3)

[0111] Accordingly, in this region we can expect a sound level reduction of 6dB for every doubling of the mass per unit area of the wall. Therefore in theory one can achieve perfect sound insulation in the mass region with a barrier that has infinite thickness and / or density (infinite mass per unit area). In the context of a sound insulating PAD, the objective is to block as much sound as possible given the mass budget and aesthetic budget.

[0112] If we consider a mass per unit area of 3.9kg / m2(the equivalent mass per unit area of a 0.5mm thick wall of steel) at 2000 Hz, then Equation (3) predicts a STL of 30 dB. If we were to double the mass per unit area to 7.8kg / m2(the equivalent mass per unit area of a 1mm thick wall of steel) then Equation (3) would predict a STL of 36 dB. Given that humans have difficulty with detecting changes of l-3dB or so, although this may be significant in a noise protection context, then a difference of 6dB is an underwhelming result for having doubled the mass per unit area of the wall. However, what if instead of doubling the mass per unit area of one wall, a second identical wall was created and placed at a defined distance away from the first? Would we achieve 30 dB + 30 dB = 60 dB of STL with the same total mass per unit area amongst the two walls? The answer is not quite, but the STL difference will be substantially higher than 6 dB.

[0113] The reason having two walls in series does not always produce double the STL of a single wall is because the fluid that exists between these two walls acts as a spring, and thus the two walls are not fully dislocated from each other with a small fluid gap, e.g. a 5mm airgap. Assuming the fluid between the walls is air, then the air spring enables resonance (called mass-air-mass resonance) to occur at the frequency given by Equation (4) where fmamis the mass-air-mass resonant frequency in Hz, m1is the mass per unit area of the first wall in kg / m2, m2is mass per unit area of the second wall in kg / m2, and D is the distance between the inner surfaces of the walls in millimeters (aka “wall to wall distance”).>

[0114] Far below fmamthe pair of walls produce an STL that is equivalent to a single wall with a mass per unit area equal to the sum of m1and m2. Close to fmam^ the pair of walls usually produce an STL less than this. Far above fmam^ the pair of walls produce an STL that is much higher than the mass law would predict for a single wall with a mass per unit area equal to the sum of m1and m2. Figure 7 graphically demonstrates this behavior where first Line 710 is what the mass law predicts for a single steel wall that is 1mm thick whilst second Line 720 is the result for a pair of mechanically dislocated 0.5mm thick steel walls with an air gap of 5mm and absorbing material in between the walls. Third Line 730 represents the same construction as second Line 720 except that the 5mm (0.2”) air gap has been increased to 100mm (4”).

[0115] As such, if achieving maximum STL is desired for a pair of walls, the objective would be to get fmamas l°w aspossible so that the largest range of sound frequencies are impacted by the benefit of having two walls in series. If we analyze Equation (4), we can see that fmam may be decreased by increasing one or more of m1, m2and D.

[0116] However, can we improve things further by adding additional walls to provide an even higher STL? For small total wall depths D, which arises from the considerations of form factor, as depicted in Figure 9, and a given amount of total mass per unit area, arising from weight considerations of the product, then two walls usually outperform any other number of walls. This is because as the total mass per unit area is divided up amongst an increasing number of walls, the average mass per unit area and wall-to-wall distance goes down. One example of this for explanation purposes is depicted with first and second Images 800A and 800B where two and three walls have the same total depth D. The wall-wall distance drops from DAin first Image 800A with two walls to DBand Dc, where DBmay or may not equal Dc, for the instance of three walls in second Image 800B. Accordingly, the mass per unit area for an individual wall decreases and the average wall to wall distance goes down which, as evident from Equation (4) act to increase the average fmam and therefore decrease STL. If trying to maximize STL with large total wall depths (say on the order of several meters), it may makesense to use more than two walls because the effect of mass-air-mass resonance diminishes across large distances. On the scale of a headset PAD, two walls will outperform any other number of walls for a given amount of total mass per unit area and total wall depth. Therefore in the context of a sound attenuating headset PAD, two walls should be used while maximizing the distance between them although the inventor notes that the Inner Cup Effect as described within this specification adds nuances to this simplification. Greater mass per unit area values within the mass budget will also in theory improve STL thanks to increasing ml or m2 in Equation (4) although as noted above a certain minimum wall thickness may be employed where increased wall thickness does not yield increased STL or sufficiently increased STL to warrant the increased mass.

[0117] Accordingly, for a PAD two walls outperform 3 or more walls because there is greater dislocation (for a given total mass per unit area and total wall depth). Accordingly, since using just air as the intervening medium between the two walls can provide significant coupling between the walls, it would be evident that establishing a more rigid connection between the walls by any means such as placing braces or solid material between them will serve to put the STL performance at risk as it breaks the dislocation and links one wall to another either at their edges, at intermediate points etc. Therefore, the walls should be as dislocated as possible. It would be evident that a material such as an open celled low density foam may be placed between the walls to potentially increase sound absorption whilst still providing a meaningful dislocation between the walls.

[0118] As noted above with respect to wall material selection stainless steel offers benefits for use as the wall material. This is because among economical manufacturing materials it has high specific acoustic impedance and specific Young’s modulus, while being corrosion resistant which makes exposed surfaces aesthetically pleasing to users and eliminates any risks associated with corrosion induced acoustic impedance matching. Another beneficial characteristic of stainless steel is that it has a high density, which means the same mass per unit area may be achieved with a smaller wall thickness, allowing for a greater wall to wall distance within the form constraint. However, in this regard copper is also an option because it also offers economical manufacturing with a material that has -13% higher density than stainless steel, steel, and iron. Given that the wall thicknesses associated with maximizing out the form constraint and mass budget are on the order of 1mm in one context that the inventor has identified, a -13% increase in density in this example will only result in 0.23mm of additional wall to wall distance. This, however, is not sufficient in many instances to overcome copper'sinferior specific acoustic impedance and specific Young’s modulus values. In addition, copper can develop a patina which poses an impedance matching risk.

[0119] Based upon the analysis above the outer wall geometry of some embodiments of the invention mimics a spherical geometry as much as possible for a high stiffness per unit of mass. Given that one side of the PAD is the human head, the PAD is hemispherical or a close approximation to a hemisphere. In addition, the distance between the two walls of the PAD should be maximized as much as possible, whilst considering the Inner Cup Effect as described in this document, and accordingly the outermost headset cup should be as large as possible within the aesthetic constraint. It can also not look strange / irregular relative to common headphone / earmuff geometries in some circumstances although this may be employed in other instances for improved performance, brand differentiation etc., see for example the Tesla™ Cybertruck geometry relative to other vehicles.

[0120] In instances where a hemispherical geometry is not appropriate, e.g. there may be restrictions such as a “height” limit of the PAD along the side of the user’s head in the vertical axis or a “width” limit along the side of the user’s head in the horizontal axis, then an elliptical geometry or other geometry may be appropriate. Referring to Figure 9 there is depicted a Rectangular PAD 910 which may be an alternate geometry within embodiments of the invention but may appear strange to observers seeing such PADs on a user. Hemispherical PAD 930 represents the stiffest shape without reinforcing etc. with the same maximum dimension, H, along the side of the user’s head as Rectangular PAD 910. The depth, labeled in Figure 9 as Depth, of Rectangular PAD 910 is set equal to the depth of the Hemispherical PAD 930. Also depicted are Profiles 920 of twelve popular headphones sold commercially. Accordingly, the Hemispherical PAD 930 of height H and depth D provides a design which is consistent with profiles of commercial headphones and should therefore not appear unusual to other individuals seeing a headset with Hemispherical PADs 930. Within an embodiment of the invention H=115 mm (4.5”) and D = 63.5 mm (2.50”) although it would be evident that other designs may be employed where D = H / 2 and H be a different value or that D = H / X. Whilst not immediately evident in Figure 9 the Hemispherical PAD 930 is actually shifted away to the right by 6mm (0.25”) such that there is actually a small rectangular section at the opening adjacent to the user’s head. This arises from the minimum height of the “collar” part around the edge of the outer cup. This dimension cannot be zero as when this is made some material must be left so the part is still one solid piece with reasonable mechanical strength. Whilst embodiments of the invention have been described with hemispherical geometries itwould be evident that a wide range of other geometries may be employed without departing from the scope of the invention.

[0121] It is a common observation that a heavy door that usually offers excellent sound isolation in a home can let a great deal of sound through if only cracked open by a small amount. STL performance is greatly reduced by leaks, so in the context of a sound attenuating headset an effort should be made to establish an air-tight seal between the earcup(s) and the user’s head. This is further complicated by the geometry variations on each side of a user’s head, the variations in shape and size of each user, and the variations of bone, muscle, skin, fat and tissue in different regions around the ear. Accordingly, a soft material such as a closed-cell EPDM (ethylene propylene diene monomer) or polyurethane foam between the PAD and head (aka a gasket) may be employed within embodiments of the invention to accommodate this. Foam as a compressible gasket material is soft for good compliance to various head geometries but may not be ideal for STL purposes for a variety of reasons. These include, but are not limited to, low specific acoustic impedance, low density, and high porosity which provide complete or partial pathways (leaks) for sound to travel through.

[0122] An economical manufacturing gasket material that may be better suited for a sound attenuating headset is silicone or an elastomer. Silicone is readily available in a variety of different durometers so that a silicone may be selected that is soft, albeit possibly not as soft as polyurethane foam. Further, silicone is non-porous with a higher specific acoustic impedance and density than polyurethane foam. Specific acoustic impedance and density may be further increased with the addition of a filler to the silicone whilst maintaining the desired level of softness. An example of a filler that has the highest density and specific acoustic impedance among economical materials is powdered tungsten. As such, tungsten powder impregnated silicone is one example of a suitable gasket material as is copper powder impregnated silicone. A thermoplastic elastomer (TPE) is another example of an economic material that is available in a variety of durometers. Generally speaking, TPEs provide higher damping than silicone (often thought of as “springy”) which in theory is beneficial to STL because a material that is higher in damping is one that is better at converting physical movement (from a sound wave for example) into heat.

[0123] Material selection is not the only variable that will determine the STL performance of a gasket as the thickness of the gasket is another important consideration. Referring to Figure 10 there are depicted first and second Images 1000A and 1000B for a Hemispherical PAD 1010 with thin and thick Gaskets 1020 and 1030, respectively. Further, the thicker the gasket the higher the portion of the PAD that is not made of the STL double wall for example, thusreducing the STL of the PAD as a whole. Accordingly, the gasket should be as thin as possible whilst still having the compliance range necessary for sealing against a defined range of head geometry variations. For example, the defined range may be defined by one or more of sex, ethnicity and age for example.

[0124] In the preceding discussion on specific acoustic impedance it was shown that a larger difference in specific acoustic impedance between two subsequent mediums results in increased sound reflection. It was also shown that a material used for a PAD cup may have a high specific acoustic impedance and that one such material is stainless steel. The lowest specific acoustic impedance material that is typically practical for use is air. Also, since sound reflection occurs every time there is a change in medium, a greater total reflection may be achieved by increasing the number of times the medium changes back and forth from high specific acoustic impedance to low specific acoustic impedance. Thus, if a wall were to be made of a large number of stainless steel layers with air in between (aka a laminate), then high STL could occur. Therefore in the context of a sound attenuating headset, lamination of the walls of the PADs can provide an improvement in STL within certain frequency ranges. For example, the inventor has tested laminated, see Figure 11 for example, and solid cups wherein the laminated cups provided improved STL over the range approximately 20 Hz to 135 Hz but were worse from approximately 135 Hz to 1,000 Hz. Accordingly, a PAD may employ two stiff cups with no lamination as the 135 Hz - 1,000 Hz region is more important in some circumstances, as typical environmental sounds and voices are in this range, but another design may employ one or more laminated cups as the 20 Hz to 135 Hz region is important due to noise from machines etc. dominating the user’s environment. In addition, in certain circumstances the mass budget will allow the possibility of having laminated cups in addition to stiff cups. In this case it may make sense to have laminated cups located on one or both sides of any number of the stiff cups present.

[0125] The energy of a sound wave can only be reflected, transmitted, or absorbed as it travels. So far the emphasis has been on decreasing transmission by increasing reflection. Decreasing transmission can also be achieved by increasing absorption. One common way that sound energy is absorbed is through the use of a porous / fibrous material such as acoustic foam, fiberglass, and mineral wool. These materials are good sound absorbers because when a sound wave travels through one of these materials, the air molecules inside vibrate longitudinally and convert some of the sound wave energy into heat through a variety of mechanisms such as viscous drag due to the small and tortuous paths they reside in. Allowing sound waves to enterthe material is important because if the incident surface pores are clogged up with paint for example, more sound will be reflected and not absorbed.

[0126] An important aspect of porous-fibrous absorbers is that they require high thicknesses to be effective at low frequencies. When placed against a wall, porous-fibrous absorbers can only appreciably absorb sound frequencies that have a wavelength equal to or less than one quarter of the absorbing material thickness. For example, a 2.5cm thick sheet of polyurethane against a wall can only appreciably absorb sound frequencies that have a wavelength of 10cm (4”) or less. This corresponds to a sound frequency of 3430 Hz or higher. Given the space available within the aesthetic constraint of the PAD a porous-fibrous absorber is unlikely to be a primary driver of STL performance below 1000 Hz. However in the context of a sound attenuating PAD, porous-fibrous absorbers can still improve STL performance. For example, a porous-fibrous material such as melamine foam, acoustic insulation such as Thinsulate™ by 3M™, polyurethane foam for example, may be disposed between an inner cup and an outer cup, between inner cups, or inside the innermost cup.

[0127] Based upon the preceding analysis and review, a design guideline for a PAD with high STL may be:• Composed of two or more walls;• Have the walls as dislocated as possible; and• The distance between the two or more walls should be as high as possible although the Inner Cup Effect identified by the inventor also establishes that the inner cup cannot have an internal volume that is too low or be too close to the user’s ear drum.

[0128] For example, the outermost cup may be hemispherical over a significant portion with a diameter of 115mm (4.5”) such that the PAD approximates the largest outer geometry of popular headphone products and provides the stiffest shape per unit mass. However, as noted the geometries of the inner and outer cups may have different geometries and geometries other than hemispherical may be employed without departing from the scope of the invention. Where two or more walls are employed, their thicknesses may or may not be equal.

[0129] Where the PAD is designed with Stiffness Driven Walls then stainless steel presents a good material of choice as it:• has the highest specific acoustic impedance among economical manufacturing materials.• has the highest specific Young’s modulus among economical manufacturing materials leading to a greater stiffness per unit of mass.• has a high density among economical manufacturing materials, allowing for a greater wall to wall distance given the form factor and Inner Cup Effect constraints.

[0130] However, it would be evident that materials other than stainless steel may be used that offer high specific acoustic impedance, high specific Young’s modulus and a high density.

[0131] Further, the design thickness of the walls for improved STL with a Stiffness Driven Wall whilst staying within the mass budget should be as thick as possible unless as noted above the thickness reaches a point where increasing the wall thickness does not offer improved STL or sufficient improvement to justify the increased mass. In theory, increased wall thickness means a greater mass per unit area and therefore increased STL in the mass region, greater stiffness, which means increased STL in the stiffness region and a greater mass per unit area, which decreases the mass-air-mass resonant frequency and improves STL above this frequency.

[0132] A damping material could be applied to the Stiffness Driven Walls to eliminate some of the poor STL performance in the resonance and coincidence regions. Optionally, the Stiffness Driven Walls may be bare without coatings, paint etc. in order to avoid the risk of decreasing STL via impedance matching.

[0133] Where the PAD is designed with Mass Driven Walls then the design could exploit compositing or laminated walls with or without a porous-fibrous absorber between them, for example, for high frequency STL.

[0134] In either case a gasket material can be employed providing high specific acoustic impedance such as silicone, elastomer, TPE, or silicone / elastomer impregnated with an additive such as tungsten powder. The gasket may be as thin as possible while still having the compliance necessary for sealing against a given range of head geometry variations and variations in underlying structure of the head. In order to enable this, the edges of the walls should closely conform to the surface of a typical human head. As noted above the edges of one or both walls may be established in dependence upon a defined range of individuals whereby different edge profiles may be employed with different defined ranges where each range is established for one or more of age, ethnicity, sex, etc.

[0135] Within this section the inventor presents comments on the design rules based upon their experimental testing. With respect to the PAD being composed of two walls the inventor has observed that the addition of a third wall in between two existing walls can make things slightly better or worse without controlling for the total mass of cups used. In the scenario that adding the third wall makes STL worse, this leads us to the same conclusion that the theory does, namely 3 walls is not advisable. In the scenario that adding the third wall makes thingsbetter, for example, then this is conceivable because we are increasing the total mass used in the system (aka an increased mass budget). Whilst designs with three walls may be established with high STL the inventor considers that two walls provide for high STL with a design with appropriate economics as the walls will generally be the most expensive elements of many embodiments of the invention.

[0136] With respect to dislocation of the walls the inventor has noted that mechanically connecting the two walls, which they refer to as the outer cup and inner cup, results in poor STL performance. The inventor found that suspending the inner cup in “mid-air” with 4 elastic strings provided no additional STL performance when compared to having the inner cup rest on some low density polyurethane foam that touched both the inner and outer cups. Therefore, it is possible that there is a point at which additional dislocation provides little or no additional STL performance improvement. Accordingly, the design goal can be to achieve an adequate level of dislocation.

[0137] With respect to the distance between the walls being as high as possible then the inventor presents comments below for the outer and inner cups.

[0138] A larger outer cup improves STL performance significantly in all experiments. In experiments the inventor found that increasing the diameter of a cylindrical outer cup improved STL performance whilst maintaining an inferior air gap height-wise. Thus the STL performance is not just dependent on the smallest air gap present (what the inventor refers to as the “bottleneck” or limiting factor), it benefits from a larger air gap due to increasing the size of the outer cup surface in general.

[0139] Based upon the inventor’s experiments one may think that to establish the greatest air gap and therefore STL performance one should have the maximum size possible for the outer cup and the minimum size for the inner cup, with the inner cup being just large enough to seal around the ear canal of the user. However, the inventor has found that when the inner cup gets small enough with a given outer cup, STL performance drops. The inventor has coined this the “Inner Cup Effect”. A larger or smaller inner cup may be employed within embodiments of the invention to provide a different trade off in STL across different frequency ranges. For example, a PAD may be designed to block very low frequencies (e.g. 125 Hz) may employ a differently sized inner cup than a PAD intended to block higher frequencies (e.g. 1 kHz). A hypothesis for an explanation of the Inner Cup Effect is that just as a greater distance between walls can serve to reduce dislocation between them and increase STL, a greater distance between the inner cup and ear drum can also serve to reduce the dislocation between them and increase STL. Thus, with all else being equal an inner cup with a greater internalvolume can improve STL especially since it allows for more porous-fibrous material to be included inside the inner cup, however it is noted that this decreases the volume available to reside between cups. For every size of outer cup there is a corresponding optimal size for the inner cup that achieves a balance between the competing forces of increasing wall gap and trying to avoid the Inner Cup Effect for the frequency ranges of interest. A larger or smaller inner cup may be employed within embodiments of the invention to provide a different trade off in STL across frequencies. For example, a PAD intended to block very low frequencies (e.g. 125 Hz) may employ a different sized inner cup than a PAD intended to block higher frequencies (e.g. 1000 Hz).

[0140] Within experiments the inventor found a suitable design for the inner cup was that of a cylindrical steel round tube with a stainless steel flat circular disk sealing one end and that the inner height should be approximately half its inner diameter for optimal STL performance. It is interesting to note that given that the ear canal resides approximately in the center of the round tube, when the inner height is equal to half the inner diameter, the inner height is no longer the “bottleneck” in that it no longer causes the circular disk to be the surface that solely determines the surface that is closest in proximity to the ear canal. The Inner Cup Effect could appear to depend heavily on the minimum distance to a wall, and it could depend mainly on the internal volume of the inner cup. Given that the minimum diameter of a round tube that fully surrounds a significant proportion of human ears is around 70 mm (2.7”), the corresponding internal height could be around 35 mm (1.35”). In this example the hemispherical outer cup was 115mm (4.5”) in diameter with a wall thickness of approximately 1mm (0.040”) and the cylindrical shaped inner cup was 70mm (2.75”) in diameter with a wall thickness of 1.2mm (0.047”). The inventor has also tested inner cups of hemispherical geometry and cylindrical tube with a hemispherical end, see Figure 13 for example. It would be evident that the hemispherical end via its different geometry presents a different tradeoff between wall gap and the Inner Cup Effect. The initial measurements by the inventor indicate that an inner cup which is hemispherical performs worse than an inner cup formed from a round tube with a flat circular disk closing the end distal to the user’s ear for a frequency range of interest. This possibly suggests that the internal wall of the inner cup may be designed to not just decrease the minimum distances from the user’ s ear / ear drum location to the inner surfaces of the inner cup, but also to not concentrate internal sound reflections toward this location or even sending internal sound reflections away from this location to create more of an acoustic “dead spot” in this region. It may also indicate that an inner cup with a lower internal volume was not advantageous in the frequency range of interest.

[0141] In order to verify that stainless steel would be appropriate as a Stiffness Driven Wall material the inventor has tested PADs of identical geometry in steel and aluminum with steel showing superior performance through its higher density, stiffness, and specific acoustic impedance as predicted and discussed above. The inventor has also tested doubling the steel wall thickness of the inner and outer cups from 0.065” to 0.125” which yielded no or little STL improvement in a frequency range of interest. This agrees with the prediction of the mass law which predicts underwhelming STL results upon doubling the mass of a wall, and generally low STL at low frequencies. This doubling of mass also represents a roughly eightfold increase in stiffness which indicates that once a defined point has been reached then subsequent increases in stiffness can yield no additional performance benefit. In order to further test this the inventor installed a large amount of braces into an outer cup making it incredibly stiff but no significant measurable STL difference was found in a frequency range of interest. Further, this also indicates that some other wall materials, whilst having superior specific Young’s modulus value which can provide more stiffness per unit of mass, may not be as appropriate as additional stiffness may not be required. For example, although alumina has a higher specific Young’s modulus it has a lower density, lower specific acoustic impedance and is more expensive to manufacture with than stainless steel.

[0142] Within embodiments of the invention a damping material may be applied to the cup walls as this can provide an improvement in STL within and around the resonance and coincidence regions. If we consider the resonance region then this begins slightly before the first resonant frequency and on the basis that a damping material improves STL due to resonance effects above and around the first resonant frequency, which the inventor measured for one embodiment of the invention to be approximately 1000Hz and 290Hz for the inner and outer cups respectively, the effects of damping are expected to be present over a meaningful portion of the human hearing range. With respect to the coincidence region, which begins slightly before the critical frequency, then as discussed above a thicker wall results in a reduction in the frequency at which STL starts to be lower than the mass law would predict due to coincidence effects. If we assume that the thickest wall of stainless steel on the headset is 1.2 mm (0.047”) then Equation (2) above predicts that damping will improve STL due to coincidence effects above -10,500 Hz. Accordingly, in theory the effects of damping in the context of a sound attenuating headset are expected to be effective at a significant range of frequencies within the human hearing range. The inventor notes that in experimental testing, the addition of a damping material to cups was not shown to provide a significant improvement in STL, and impedance matching serves as a possible explanation.

[0143] Whilst the description above has stated that stainless steel cups may be bare, with no coatings, paint etc. the expectation is that thin surface protection coatings, surface decorative coatings etc. should not make a significant difference to the STL of a headset exploiting PADs designed according to the guidelines and designs outlined within this specification. However, it is evident that if the stainless steel is uncoated then the PADs offer better performance in theory. For example, a glass bead blast to the visible stainless steel surfaces is an economical way to provide a high-end finish to the outer surfaces etc.

[0144] Within the preceding description PADs according to embodiments of the invention may be implemented with limp walls generally intended to be mass driven rather than stiff cups and one mechanism to effectively providing a limp cup is through compositing.

[0145] According to the simplified theory discussed above a Mass Driven Wall has identical STL performance to a Stiffness Driven Wall above the resonant frequency but is worse below the resonant frequency, and therefore it appears that there is little reason to use a limp cup but a limp cup may be employed within other embodiments of the invention.

[0146] Accordingly, a design of a PAD targeting this design regime would be, for example, one employing a dense material, e.g. tungsten powder, within a matrix, for example a silicone or elastomer matrix. Such a loaded matrix allows this “limp” cup, as the inventor refers to it, to have a low resonant frequency, increasing the frequency range of the mass region in the STL-frequency curve, see first Image 300A in Figure 3. The filler gives the wall a higher mass per unit area, so the mass law provides an improvement in STL while consuming as little space as possible and / or providing an increased wall gap. Appropriate selection of the filler, for example tungsten, may also provide a STL performance enhancement where the material has a high specific acoustic impedance. However, it would be beneficial in many instances to provide a wall gap or soft material region between a limp cup and a stiff inner cup so that they are dislocated.

[0147] In embodiments of the invention a limp cup may be employed on the inner or outer surface of an inner cup rather than the outer cup as a higher mass per unit area may be achieved for a given total mass allocation of the PAD. If a limp cup is added to the outside an inner cup the wall gap will be consumed directly, whereas adding it to the inside of an inner cup would consume wall gap indirectly due to needing to accommodate the solid inner cup dimensions for the Inner Cup Effect. In either scenario, the design rationale is that the addition of a Mass Driven Wall could improve STL despite a decrease in wall gap.

[0148] The inventor also notes that a silicone matrix with a filler, such as tungsten powder or copper powder, may also be employed as a gasket material around the edges of an innerand / or outer cup. The gasket, with or without filler, is the portion of the PAD that contacts the user’s head to accommodate variations in user head profile, head dimensions etc. However, the gasket rather than being silicone may be another soft compliant material such as a natural rubber, latex, an artificial rubber, an elastomer, thermoplastic elastomer, or foam.

[0149] Within the preceding specification the concept of lamination was presented with respect to the formation of an inner and / or outer cups or being added to one or more sides of an inner or outer cup. Referring to first Image 1100A in Figure Il a method of forming prototype cups is presented although it would be evident to one of skill that other approaches may be employed without departing from the scope of the invention. Second Image 1100B in Figure 11 depicts prototype laminated Inner Cup 1150 and Outer Cup 1160. First Image 1100A depicts a cross-sectional diagram of a laminate cup before a force is applied on the perimeter for the duration of the epoxy curing.

[0150] The prototype laminated cups were made from two parts: a cylindrical shaped side wall and a circular shaped top. The side walls were made by taking a single long strip of 0.005” thick steel Shim Stock 1110 which was rolled into a tight coil. Two long strips of green Tape 1120 were used on these long steel strips to ensure that each layer of Shim Stock 1110 was largely separated by a thin layer of air. The ends of the coil were sealed with Epoxy 1130. The tops for these laminated cups were made by taking a number of circular cutouts from steel Shim Stock 1110, putting three short strips of Tape 1120 on each, and assembling them into a stack. Applying Epoxy 1130 to the appropriate areas and allowing it to cure while the apparatus is under pressure makes for a cup that is free of air leaks from the outside of the cup to the inside of the cup. The result is a structure where a sound traveling from the outside to inside of the cup encounters several medium changes from low to high specific acoustic impedance.

[0151] Experimentally the STL of these laminate cups was compared to solid steel cups with a wall thickness equal to the sum of all wall thicknesses in the laminated cups. Laminate cups were shown to be superior to solid steel cups from roughly 20 Hz to 135 Hz but were worse from 135 Hz to 1,000 Hz. The frequencies for which stiff cups are superior spans a larger range that also captures more of the frequencies contained in human speech. The fundamental frequency of a male voice (the lowest that it can go) is something like 100 Hz. The rest of the frequencies contained in human speech are therefore above 100 Hz. Since the human voice is one of the most common sounds that is desired to be eliminated, it stands that two stiff cups would provide improved performance in many circumstances although a laminated cup configuration may provide a different performance tradeoff in other products.

[0152] However, the addition of a laminate cup to the outside and / or inside of an outer or inner cup could certainly improve STL particularly at low frequencies. In this case it would be wise to add the laminate cup to the outside and / or inside of the inner cup to be more efficient with the mass budget, while controlling for internal dimensions of the inner cup to be mindful of the Inner Cup. It was also shown from experiments performed by the inventor that increasing the number and thickness of laminate layers results in higher STL and dividing the total laminate layers amongst both cups rather than dedicating them all to the inner cup results in approximately the same STL in a frequency range of interest.

[0153] Overall, laminates can provide effective increases in STL in a notoriously difficult frequency range (20 Hz to 135 Hz). It is interesting to note that such STL performance is achieved despite the extremely small wall to wall distances and wall thicknesses.

[0154] The inventor has found during experiments that filling the gap between the inner and outer cup with a porous-fibrous material decreased STL which they associated with making the cups less dislocated. Also, the addition of porous-fibrous material and / or felt to the inner or outer surfaces of the inner or outer cup did not improve the measured STL in a frequency range of interest with exception to adding felt and / or a porous -fibrous material to the inside of the inner cup. The improved STL obtained by adding a thin layer of felt or similar material to the inner surface of the inner cup was attributed to making the interior of the inner cup, “room”, that the ear is in less echoey without making the room too small which would allow the Inner Cup Effect to creep in. The improvement with felt was notable at high frequencies (3 kHz and higher). In addition to the use of felt, as noted earlier the addition of a porous -fibrous material to fill a large portion of the inner cup’s internal volume was shown to increase STL significantly.

[0155] Referring to Figures 12 and 13 there are depicted views of exemplary PADs according to embodiments of the invention which are intended to provide high STL using the theory and experimental results whilst remaining within the aesthetic constraint, mass budget, and economical constraint. Within these sealing mechanisms have been omitted for clarity. The inner cup in Figure 12 has a larger internal volume and a different internal surface compared to that of Figure 13, so these PADs may be expected to have different STL performance. Notably, the internal cup of Figure 13 points a large portion of the sound that is within the Inner Hemisphere 1340 towards the ear drum. In contrast the round tube (Inner Collar 1250 in Figure 12) and flat circular disk (Disk 1240 in Figure 12) in theory directs less sound at the ear drum which could contribute to the experimentally demonstrated improved performance alongside the inner cup internal volume increase. Within other embodiments of the invention the innercup whether made from one part or many, may be profiled or shaped to direct acoustic energy away from the user’s ear drum. This may include directing one or more acoustic absorbers within the inner region of the inner cup. A structure similar to an anechoic chamber with geometry intended to increase the amount of porous -fibrous material that sound travels through for high sound absorption may also be employed.

[0156] Referring to Figure 12, first Image 1200A depicts three-dimensional exploded assembly views of a design employing an inner cup with a flat circular disk whilst first Image 1300A in Figure 13 depicts three-dimensional exploded assembly views of a design employing an inner cup with a hemispherical end. Second and third Images 1200B and 1200C in Figure 12 depict cross-section and perspective views of the assembled PAD with a flat circular disk whilst second and third Images 1300B and 1300C in Figure 13 depict cross-section and perspective views of the assembled PAD with a hemispherical end to the inner cup.

[0157] As depicted in first Image 1200A the PAD comprises:• Outer Hemisphere 1210 of the outer cup;• Outer Collar 1220 of the outer cup;• Foam 1230 which is disposed between the outer cup and inner cup;• Disk 1240 of the inner cup; and• Inner Collar 1250 of the inner cup.

[0158] Exemplary dimensions, manufacturing process and material for these being given in Table 1 below.Table 1

[0159] As depicted in first Image 1300A the PAD comprises:• Outer Hemisphere 1310 of the outer cup;• Outer Collar 1320 of the outer cup;• Foam 1330 which is disposed between the outer cup and inner cup;• Inner Hemisphere 1340 of the inner cup; and• Inner Collar 1350 of the inner cup.

[0160] Exemplary dimensions, manufacturing process and material for these being given in Table 1 below.Table 2

[0161] Within the designs depicted in Figures 12 and 13 the outer and inner cups are each formed from two parts, for example, a collar and either a hemisphere or circular disk to close the end of the collar off. To avoid any sound leakage at the interface, these two parts would be attached to one another in an air-tight fashion although it may be beneficial to have a small diameter hole, e.g. 0.127 mm (0.005”), somewhere on the inner cup to provide pressure relief to the ear drum when the user is wearing and putting on the PAD.

[0162] Within embodiments of the invention the inner cup, comprising for example Inner Collar 1250 and Disk 1240 in Figure 12 or Inner Collar 1350 and Inner Hemisphere 1340 in Figure 13; is disposed within the outer cup, comprising Outer Hemisphere 1210 and Outer Collar 1220 in Figure 12 or Outer Hemisphere 1310 and Outer Collar 1320 in Figure 13, and its position within the outer cup may vary such that a portion of the outer cup is external to the inner cup. This portion may be zero or 100%. The dimensions given in Tables 1 and 2 are exemplary geometries and accordingly it would be evident that these may vary in other embodiments of the invention and may differ between different axes etc. For example, theposition of the inner cup may change as the PAD is worn by a user and their ear (where the PAD is an on-the-ear design) or a region of their body around their ear (where the PAD is an over the ear design) pushes the inner cup away as the outer cup moves and contacts their head.

[0163] Within embodiments of the invention the inner cup dimensions, defined by the lateral dimensions of the Inner Collar 1250 / 1350 may be defined such that the inner cup fits over the ear of a user or a defined portion of a population of users. Within other embodiments the lateral dimensions of the Inner Collar 1250 / 1350 may be defined such that the inner cup fits over a defined portion of the ear of a user or a defined portion of a population of users. The Inner Collar 1250 / 1350 may be symmetric (for example Inner Collar 1250 / 1350 is shown to be circular in an axis) or within other embodiments of the invention asymmetric in geometry.

[0164] Within embodiments of the invention such as described and depicted with respect to Figures 12 and 13, the outer cup geometry is described as hemispherical with a collar. However, it would be evident that the outer cup may be established with a spherical profile but rather than hemispherical (i.e. 50% of a sphere) the outer cup defines less than 50% of the sphere or more than 50% of the sphere.

[0165] Within another embodiment of the invention the inner surface of the cup may be spherical but the outer surface may be defined by another profile.

[0166] Within other embodiments of the invention at least one of the inner surface and the outer surface of the outer cup may be a defined portion of an ellipsoidal surface having a defined major axis and defined minor axis. Similarly, at least one of the inner surface and the outer surface of the inner cup may be a defined portion of another ellipsoidal surface having another defined major axis and another defined minor axis.

[0167] Within other embodiments of the invention, at least one of the inner surface and the outer surface of at least one of the outer cup and inner cup may be defined by one or more mathematical functions.

[0168] Within other embodiments of the invention at least one of the inner surface and the outer surface of at least one of the outer cup and inner cup may be defined by one geometrical shape or a combination of one or more geometrical shapes.

[0169] Figure 14 depicts an exemplary assembled headset with left and right PADs 1410 and 1420 respectively together with Supports 1440 and Headband 1430. Left and right being defined from the perspective of the user wearing the PADs. However, it would be evident that the Supports 1440 and Headband 1430 may be part of a common headband or disparate elements. The design of such Supports 1440 and Headband 1430 being known in the art may be of many different designs. Within some embodiments a single PAD may be employed.

[0170] In both scenarios shown in Figures 12 and 13, by default the foam pushes the inner cup outward away from the outer cup such that the inner cup is the first to make contact with the head when the headset is being put on. The pressure of the PAD against the user’s head may be established by elastic potential energy stored in a headband that thereby pushes the PAD towards the user’s head such that the foam compresses until both the inner and outer cups create a seal against the user’s head. Since polyurethane foam, which may be used in some embodiments of the invention, is easily compressible and low density, it offers adequate dislocation between the inner and outer cups. The foam is required to act as a spring in this context because the headband is only attached to the outside of the outer cup, and therefore it can only exert a direct sealing force on the outer cup. The foam serves as a way to apply the force necessary to get a seal against the head with the inner cup using the same elastic potential energy in the headband. This makes for a simple, robust, and inexpensive solution for achieving a seal on the inner cup.

[0171] Within embodiments of the invention the inner cup is “suspended” and retained within the outer cup by the foam at one end and the gasket at the other end which will be adjacent to the user’ s head. Optionally, other means of applying pressure other than from elastic deformation of a headband may be employed.

[0172] Referring to Figure 15 there is depicted an image of a Collar Edge 1520 of a Collar 1510 which may be achieved using laser cutting or laser tube cutting which has an everchanging angled / beveled Collar Edge 1520 for 360 degrees around the collar perimeter for greater compliance to the typical human head geometry.

[0173] Referring to Figure 16 there is depicted a cross-section of a PAD according to an embodiment of the invention with a silicone Gasket which comprises Head Engaging Surfaces 1610, which engage against the side of the user’s head and Membrane 1640 which seals the gap between the inner and outer cups from ingress of debris, dust etc.

[0174] The Head Engaging Surfaces 1610 at the edge(s) of the silicone Gasket are retained in position by an Adhesive, for example a commercial silicone adhesive Sil-Poxy, between a Gluing Feature 1630 which also forms part of the silicone Gasket and Tape 1650. Tape 1650 may be silicone tape, for example, of a defined width, e.g. 6mm (0.25”) wide. The adhesive adheres to the silicone Tape 1650 and silicone Gasket such that the silicone Gasket stays attached to the inner and outer cups.

[0175] The Head Sealing Surface 1610 is the feature that gets compressed between the user’s head and the collars to make a “seal.” It may have reduced thickness when the collar profiles conform to the shape of a typical human head.

[0176] Referring to Figure 17 there is depicted a PAD 1710 according to an embodiment of the invention as described with respect to Figure 16 where a Fitting 1720 provides for attachment of a headband to the PAD 1710. As evident the Fitting 1720 is positioned vertically offset from the axis of the PAD 1710 where this offset of the Mounting 1720 relative to the axis of the PAD 1710 creates a non-uniform distribution of pressure on the user’s head wherein more of the pressure is applied to the softer portions of the user’s head below their ear than to the harder portion above their ear which is primarily skull with little intervening tissue. Such a Mounting 1720 is depicted within Figure 20 with the Headband 2030 attached via Screws 2040.

[0177] Whilst the designs described and depicted are intended for PADs with high STL such that extended use may be provided without concerns over electrical power etc. it would be evident that the overall design may be combined with other prior art concepts such as Active Noise Canceling (ANC) wherein a loudspeaker within the inner cup would provide the appropriate acoustic signals to null the incoming environmental acoustic signals that do propagate through the high STL design of the inner and outer cups. These acoustic signals may be generated by analogue ANC circuits or digital ANC circuits, or both. Optionally, each side may be provided with different acoustic signals to reflect the differences in acoustic environment on either side of the user’s head. In order to establish the acoustic signals that should be nulled one or more microphones may be associated with the ANC circuit where each microphone of the one or more microphones may be internal to the PAD or external to the PAD. For example, one microphone may be disposed on the outer surface or body of the outer cup and another microphone on the inner surface or body of the inner cup. Optionally, a microphone may be disposed between an inner cup and an outer cup of a PAD, or between inner cups of a PAD.

[0178] The ANC circuits may also process the external sounds in an "awareness mode” wherein external sounds are processed prior to being provided to a loudspeaker of the PAD or an earbud of the user. This awareness mode may be halted when a loud sound is detected (e.g. a gunshot). Within embodiments of the invention processing may be implemented between the external microphone and internal loudspeaker such that the awareness mode, i.e. coupling external sound to the user, is triggered based upon detecting speech generally or a keyword spoken by an external user. Similarly, with processing coupled to an internal microphone the awareness mode may be triggered by the user speaking a particular keyword such that it is only turned on when required rather than if the user mumbles, coughs, hums or sings etc. Within other embodiments of the invention the awareness node may be configured by default, by the user or by software in execution upon a processor associated with the PAD such that is allexternal sounds or a specific category (or categories) of external sound such as alarms and / or speech for example. Optionally, the specific category (or categories) of external sound may be provided to the user at a lower level than that detected externally (e.g. partially muted), at the same level or at a higher level (e.g. raise the volume of an alarm only or raise the volume of the alarm).

[0179] Within other embodiments of the invention the loudspeaker may provide information or content to the user discreetly or in combination with active noise canceling. It would be evident that PADs may be combined with a commercial in ear loudspeaker, commonly referred to an ear-bud, such as Apple Airpod™ or Bose QuietComfort ™ earbuds for example. The PAD being worn over the earbud(s) once the user puts them on. In this manner the PAD can provide broadband noise suppression, and the user can employ the earbuds at a reasonable volume as they are not required to overcome the ambient noise. The earbuds can also employ ANC for even greater STL.

[0180] Within embodiments of the invention a PAD with a loudspeaker may provide what is referred to as “sound masking” wherein the loudspeaker plays white noise or specially formulated sound for example such that the intelligibility of speech is reduced significantly such that spoken acoustic signals reaching the user are masked making it easier for the user to focus. For example, a low complexity solution would be a battery powered speaker with an on - off button. When the button is on, a sound masking sound is played, and when it is off, no sound is played. Worn earbuds or a loudspeaker may also play sound masking to decrease speech intelligibility for example.

[0181] Within an embodiment of the invention the inner cup and / or outer cup may have one or more additional membranes disposed within it or on top of it either in designs for use without earbuds or designs for use with earbuds. A thin taut membrane provides high STL below its resonant frequency. Accordingly, within the context of a sound attenuating headset the one or more membranes may be disposed internal to the inner / outer cup or external to the inner / outer cup where the resonant frequency is established desirably at or above the upper frequency limit of the sound attenuating headset, e.g. at or above 20 kHz for a blocking PAD covering the full range of human hearing. A high resonant frequency membrane would employ a membrane which is very thin and low density to keep the membrane mass low, thin neighboring air cavities which entail low surrounding air mass, and high tension in the membrane so that it has high stiffness. The membrane may have a defined profile such that the distance of the membrane from the user’s aural canal varies.

[0182] Within an embodiment of the invention the membranes may be formed into a grid or a regular structure or irregular pattern, for example, such that the size / footprint of each individual membrane is reduced and its resonant frequency increased whilst covering a larger area within the PAD.

[0183] Figure 18 depicts Cross-Section 1800A and partial three-dimensional Perspective View 1800B of a personal acoustic device employing a membrane in association with a cup according to an embodiment of the invention. It would be evident that the design depicted is an example of how to form part of a personal acoustic device and that other design solutions may be implemented without departing from the scope of the invention. Further, whilst the description is with respect to a circular cup geometry the design concept may be applied to other non-circular geometries without departing from the scope of the invention. Whilst Figure 18 is depicted with a particular design for a cup it would be evident that the deployment of membranes could be internal, external, or both internal and external to a cup or a set of cups.

[0184] A Tube 1880 has a Flange 1850 disposed externally at an open end. A Circular Disk 1820A is disposed at the other distal end of the Tube 1880 either integral with the Tube 1880 or attached to the Tube 1880. Also disposed around the exterior of the Tube 1880 at the same end as the Circular Disk 1880 are first and second Upper Membrane Rings 1810A and 1810B above the Circular Disk 1820A and a Side Membrane Ring 1820B below the Circular Disk 1820A. An Upper Ring 1870 is disposed on the Circular Disk 1820A. An Upper Membrane 1890 has its periphery disposed between the first and second Upper Membrane Rings 1810A and 1810B and extends across the Upper Ring 1870.

[0185] The Ueft Side 1800C of Cross Section 1800A demonstrates mechanisms for tightening membranes, whilst the Right Side 1800D of Cross Section 1800A demonstrates mechanisms for holding onto the ends of membranes. The following description describes the elements of both. A Side Membrane 1830 has its upper edge disposed between the Circular Disk 1820A and Side Membrane Ring 1820B and its lower edge disposed between first and second Uower Membrane Rings 1840A and 1840B. A first Fitting 1860A pulls the first and second Upper Membrane Rings 1810A and 1810B down against the Circular Disk 1820A so that the Upper Membrane 1890 is taut whilst a second Fitting 1860B clamps the Side Membrane Ring 1820B against the Circular Disk 1820A to retain the upper edge of the Side Membrane 1830. A third Fitting 1860C pulls the first and second Uower Membrane Rings 1840A and 1840B down so that the Side Membrane 1830 is made taut. With a fourth Fitting 1860D the lower edge of the Side Membrane 1830 is retained between Lower Membrane Rings 1840A and 1840B. It would be evident from partial three-dimensional Perspective View 1800Bthat the Side Membrane 1830 and Upper Membrane 1890 are retained at multiple locations around the personal acoustic device elements depicted in Cross-Section 1800A and partial three-dimensional Perspective View 1800B. Rather than having one of each Fitting 1860A and 1860C as depicted in Left Side 1800C and 1860B and 1860D as depicted in Right Side 1800D, multiple instances are employed around the perimeter to ensure the membranes are taut across their entire surface areas.

[0186] Accordingly, the Upper Membrane 1890 is fitted externally to the closed end of the cup and the sides are externally fitted with the Side Membrane 1830. Within other embodiments of the invention rather than mechanically making the membrane(s) taut they may be formed from a material which contracts upon heating, such as polyolefin or polyvinyl chloride for example.

[0187] Within embodiments of the invention two or more membranes may be disposed in series such that the set of membranes provide high STL. This structure also results in low air mass between pairs of membranes as the membranes may be placed close together or formed in series with small air gaps. One option for the membrane is biaxially-oriented polyethylene terephthalate, commonly referred to as Mylar®, as it is a material that can withstand extremely high stresses with a low thickness. The membrane may be disposed over the outer edge of the inner cup or at a position defined within it to support compatibility with earbuds etc.

[0188] Referring to Figure 19 there is depicted a Cross-Section View 1900A of a personal acoustic device employing a membrane stack in association with a cup according to an embodiment of the invention using a similar mechanical configuration as described and depicted in Figure 18. However, the Upper Membrane 1690 in Figure 18 is replaced with Upper Membrane Stack 1910 and the Side Membrane 1630 in Figure 18 is replaced with Side Membrane Stack 1920. As depicted in View 1900B a membrane stack, such as Upper Membrane Stack 1910 and Side Membrane Stack 1920 comprises a number of Membranes 1950 with Spacers 1940 between them. Within an embodiment of the invention, as mentioned previously the Spacers 1940 may be designed to employ a variety of smaller membranes such as a grid or honeycomb structure for example which would increase the resonant frequency of the membranes.

[0189] The structures depicted within Figures 18 and 19 within embodiments of the invention may be viewed as representing an inner cup or outer cup of a PAD such that it is combined with another cup according to an embodiment of the invention to provide the other of the outer cup and inner cup. However, the membrane may be viewed as a cup itself such that within other embodiments of the invention it may be employed and dislocated in differentmanner compared to an outer cup and inner cup with foam between them. The membrane is dislocated in the sense that it can vibrate and resonate freely from the stiff cup. Accordingly, within other embodiments of the invention a single stiff cup with a membrane such as depicted in Figure 18 may be viewed as a dual cup system just like the standard stiff inner and outer cup setup with foam in between. Whilst the membranes in Figures 18 and 19 are depicted as having a lateral dimension equal to that of the overall stiff cup it would be evident that within other embodiments of the invention the membrane may be smaller than the overall cup such that it’s points of mechanical contact to the stiff cup are different. Such an example being depicted within Cross-Section 1900C wherein the Membrane 1940 is within the Outer Cup 1950 but the Membrane 1940 now comprises Inner Portion 1940A and Outer Portion 1940B that have different designs or materials such that the rigidity of each of the Inner Portion 1940A and Outer Portion 1940B are different. Accordingly, the Outer Portion 1940B may be of higher rigidity such that the Inner Portion 1940A acts as the Inner Cup in conjunction with the Outer Cup 1950. Within another embodiment both the Inner and Outer Cups may be membrane designs with different, similar or the same properties.

[0190] Now referring to Figures 20 and 21 there are depicted headsets employing personal acoustic devices according to embodiments of the invention without and with silicone covers over shaped collars profiled to fit against the wearer’s head. Each PAD, as depicted in Figure 20, comprises a Collar 2020 on the rim of the Hemispherical Outer Cup 2010 which is profiled according to a contour of the wearer’s head. The edge of this Collar 2020 being covered with a Cover 2110 which as depicted in Figure 21 extends along the external surface of the Collar 2020 and PAD but may only be around the edge of the Collar 2020. Also depicted in Figure 20 is the Headband 2030 which is attached to both Hemispherical Outer Cups 2010, one for the user’s left ear and the other for the user’s right ear, via Screws 2040 which engage with Mountings 1720 as depicted within Figure 17. The offset of this Mounting 1720 relative to the axis of the PAD, in conjunction with the typical sprung action of the headset attached to the PAD, creates a non-uniform distribution of pressure on the user’s head wherein increased pressure is applied to the softer portions of the user’s head below their ear than to the harder portion above their ear which is primarily skull with little intervening tissue.

[0191] Referring to Figure 22 there is depicted an outer cup of a personal acoustic device according to an embodiment of the invention showing the shaped Collar 2020 profiled to fit against the wearer’s head and the Hemispherical Outer Cup 2010. Within other embodiments of the invention the Collar 2020 and Hemispherical Outer Cup 2010 may be formed as single piece part. Now referring to Figure 23 there is depicted a shaped Collar 2020 profiled to fitagainst the wearer’s head forming part of an inner cup of a personal acoustic device according to an embodiment of the invention for attachment to a circular flat disk for example. One or more inner cups may also be formed as a single piece part.

[0192] Referring to Figure 24 there are depicted first and second Acoustic Spectra 2410 and 2420 for a personal acoustic device according to an embodiment of the invention with and without a liner on the inner surface of the inner cup of the PAD. The liner being a fibrous liner, for example felt formed from natural and / or synthetic fibers.

[0193] Within the description the geometry of inner and outer cups of a PAD have been described as being hemispherical. However, it would be evident that within other embodiments of the invention other geometries for the inner and / or outer cup may be employed. Examples of such alternate geometries being depicted in first and second Images 2500A and 2500B in Figure 25 and first to fourth Images 2600A to 2600D in Figure 26. An alternate geometry mimicking the profile of the human ear is depicted in first and second Images 2700A and 2700B in Figure 27. A non-hemispherical geometry attached to a collar, such as described and depicted in Figure 23, is depicted in first and second Images 2800A and 2800B in Figure 28. Non-resonant geometries may be employed for outer and / or inner cups.

[0194] Now referring to Figures 29 and 30 there are depicted cross-sections of cups for personal acoustic devices according to embodiments of the invention. In Figure 29 an outer cup of outer diameter 115 mm (4.5”) and wall thickness 0.8mm (0.032”) is depicted within which there are a series of seven inner cups each of wall thickness 0.127 mm (0.005”) which are separated by 0.127 mm (0.005”). These cups being for example steel or stainless steel. In Figure 30 an inner cup of outer diameter 70 mm (2.75”) and wall thickness 0.635mm (0.025”) is depicted beyond which there are a series of seven cups each of wall thickness 0.127 mm (0.005”) which are separated by 0.127 mm (0.005”). These cups being for example steel or stainless steel. Figure 29 and Figure 30 demonstrate that lamination may be added to the inner or outer surfaces of an inner or outer cup, which may be stiff.

[0195] Referring to Figures 31 and 32 there are depicted collar geometries according to embodiments of the invention. Figure 31 depicts Front View 3100 A, Rear View 3100B, Top View 3100C and Perspective View 3100D of a collar for an outer cup of outer diameter 115 mm (4.5”) and wall thickness 1.2mm (0.047”) where the collar is short relative to its diameter. In contrast Figure 32 depicts Front View 3200A, Rear View 3200B, Top View 3200C and Perspective View 3200D of a collar for an inner cup of outer diameter 70 mm (2.75”) and wall thickness 1.2mm (0.047”) where the collar is “long.”

[0196] Within the preceding description designs of PADs, see for example Figures 16 and 17, there has been presented a membrane disposed between an inner cup and outer cup at the side abutting the user’s head when the PAD is worn. The region between the inner cup and outer cup being filled with a fluid such as air. However, within other embodiments of the invention, the region between the cups may be a gas or gases at low pressure or extremely low pressure (which hereinafter will be referred to as “vacuum”) such that there is no medium between the inner cup and outer cup to acoustically couple them. Accordingly, referring to Figures 33 and 34 there is depicted perspective cross-sectional views of personal acoustic devices according to embodiments of the invention with a vacuum between cups. Within Figure 33 a Membrane 3330 seals the open region between edges of the Outer Cup 3310 and Inner Cup 3320. For example, the Outer Cup 3310 and Inner Cup 3320 may be stainless steel which are heated and pushed onto the Membrane 3330 which then seals against them as it melts from the hot edges of the Outer Cup 3310 and Inner Cup 3320. The membrane may also be attached to the cups mechanically with the use of high tension wrap or screws for example. Other elements of the PAD, such as described and depicted in Figures 16 and 17 for example, have been omitted for clarity. Within another embodiment of the invention the Inner Cup 3320 is “attached” to the Membrane 3330 prior to the Outer Cup 3310 being attached under vacuum.

[0197] Within Figure 34 a Membrane 3450 seals the open regions between the edges of the Outer Cup 3410 and Inner Cup 3440. However, in this design first and second Intermediate Cups 3420 and 3430 respectively are disposed between the Outer Cup 3410 and Inner Cup 3440. Other elements of the PAD, such as described and depicted in Figures 16 and 17 for example, have been omitted for clarity. Within an embodiment of the invention the Inner Cup 3440, second Intermediate Cup 3430 and first Intermediate Cup 3420 are “attached” to the Membrane 3330 prior to the Outer Cup 3410 being attached. The first and second Intermediate Cups 3420 and 3430 and Outer Cup 3410 being attached under vacuum. Within other embodiments of the invention rather than all the regions between sequential pairs of the Outer Cup 3410, first and second Intermediate Cups 3420 and 3430, and Inner Cup 3440 being under vacuum only a subset of these regions may be under vacuum such as between the first and second Intermediate Cups 3420 and 3430 for example.

[0198] The Membranes 3330 and 3450 in Figures 33 and 34 may be, for example, a silicone or a fiber reinforced silicone such that the elements mounted upon the membrane are mechanically decoupled (dislocated) whilst sealing the regions between the cups. Membrane 3450 may within other embodiments of the invention be multiple membranes such that the mechanical decoupling or dislocation between different cups varies. For example, a firstmembrane may be employed for the Outer Cup 3410 and first and second Intermediate Cups 3420 and 3430 with a second membrane between the second Intermediate Cup 3430 and Inner Cup 3440.

[0199] Referring to Figures 35 and 36 there are depicted perspective and 3D perspective cross-sectional views respectively of prototype PADs according to embodiments of the invention. Within this design an Outer Collar and Hemisphere form the outer cup, whilst an Inner Collar and Circular Disk form the inner cup. Each may be formed from a pair of pieceparts which are attached with a high quality seal such as via an epoxy or welding for example, although they may also be formed from a single piece-part instead for example via stamping or deep drawing for example. Outer and Inner Tracks are attached to the Collars with high quality sealed joints such that only small gaps exist between them for example. An epoxy or cyanoacrylate glue may fill these gaps or the gap may be closed via an interference fit for example. Another suitable method to seal one or both of these tracks to their respective collars is shown within the inset of Figure 35 described below, wherein a compressible O-ring within a groove or recess between the track and collar is compressed to create a seal, and is held in place with a snap-in feature or through compression / friction. These inner and outer tracks with their respective foams disposed on them provide a larger surface area of these foam elements which compress and create a seal against the head which has been experimentally shown by the inventor to improve performance. This suggests that a longer seal provides increased performance as this provides for each foam an improved likelihood of making a higher quality seal against the head when the PAD is positioned.

[0200] The inventor has also established experimentally that thinner / shorter Outer and Inner Foams improves performance although there is a tradeoff as these should also be thick / tall enough to seal against a defined variation in the profile of human heads allowing use by a wider subset of users. However, different track - foam combinations could be provided or offered allowing users to establish the best fit for their personal head profile or that customization may be undertaken for further improved performance by head profiling etc.

[0201] The addition of a porous-fibrous material such as melamine foam for example, a foam-like material consisting of a melamine-formaldehyde condensate, that fills the inner cup has experimentally been found to improve performance, as shown by the Acoustic Foam in Figure 36. Also as depicted in Figure 36 Finger Grips may be added for easier installation and removal of the headset by users for PAD designs without an exterior cosmetic casing. These Finger Grips may be separate parts that are held in place, for example by adhesive or threaded portions that are rotated into threads in the outer cup for example, or they may be part of theouter cup shape with no need for additional parts. The Compressible Foam, which may be polyurethane foam for example, provides the force necessary for ensuring that the inner cup seals against the head. In Figure 36 the Compressible Foam is tubular in shape such that a lower force is exerted on the head by the inner cup offering better dislocation between the inner cup and outer cup, whilst keeping the inner cup stable from moving side to side. Other geometries and other foams (or compressible materials) may be employed without departing from the scope of the invention.

[0202] The following describes sealing methods and concepts for an outer cup of a PAD according to an embodiment of the invention exploiting an additional skin over the Outer Foam, however these are also applicable to the inner cup of a PAD according to an embodiment of the invention, wherein reference is made to first and second Images 3900A and 3900B in Figure 39. Referring to first Image 3900A there is depicted schematically the addition of a simple Skin 3920 around the Outer Foam 3910 to help achieve better STL performance, improved aesthetics, and a barrier to dirt, grease etc. The Skin 3920 is depicted only in section at the end of the Outer Foam 3910 but would extend along the Outer Foam 3910. This Skin 3920 may be an elastomeric sheet with a silicone between it and the Outer Foam 3910 for example or it may be a elastomeric casing filled with another elastomeric material. Optionally, the Skin 3920 may extend down over the Outer Track 3930 and be either permanently attached or demountably attached to the Outer Foam 3910 where when demountably attached the Skin 3920 provides a low cost replaceable element.

[0203] Within second Image 3900B an Alternative Skin 3940 around the Outer Foam 3910 to help achieve better STL performance, improved aesthetics, and a barrier to dirt, grease etc. Alternative Skin 3940 is a thicker and heavier skin around the Outer Foam 3910 than Skin 3920 in first Image 3900A, which should provide improved STL performance due to providing a higher quality seal against the head, while being put under mechanical disadvantage to avoid taking significant force away from that which is needed to compress the Outer Foam 3910 to create a seal. Accordingly, Alternative Skin 3940 extends around the Outer Foam 3910 and engages against the Outer Track 3950 which may have features on its profile to engage against the Alternative Skin 3940. The Alternative Skin may be a thick elastomeric material or a thin elastomeric casing with another elastomeric material disposed within.

[0204] The inventors project from their experiments that, with everything else constant, an increased compression of the Outer Foam and / or Inner Foam produces a higher STL as typically reduces the density of the foam and accordingly decreases the surface area that sound can travel through (see Figure 10). Accordingly, a soft foam is preferred for the Outer Foamand Inner Foam elements of the PAD. One such EPDM foam being one that requires 4 psi for 50% compression and 3 psi for 25% compression, although an even softer foam may be employed. When this foam is compressed significantly, due to its density increasing and its inherently slow recovery, the material begins to approximate a solid. This offers a way to get at the STL benefits of having a gasket made out of a solid such as silicone for example, while also having the extremely compressible nature of a foam for sealing against a wide range of human head variation. The slow recovery of the foam is an indicator that it is very difficult for sound and air to penetrate this material. Even greater STL may be expected in the scenario where the foam is submerged in a liquid, sealed in by a foam skin for example. This would still allow the foam to compress significantly, whilst the remaining voids in the foam are filled with liquid rather than air, which has a higher density and specific acoustic impedance. Excess liquid would be displaced and pushed to the sides of the gasket, providing additional mass for sound to travel through. An easily stretchable and bendable skin may be employed in this context.

[0205] Accordingly, referring to Figure 35 the PAD according to an embodiment of the invention is depicted as comprising an Outer Hemisphere 3560 to which an Outer Collar 3550 is attached. Attached to the upper edge of the Outer Collar 3550 is an Outer Track 3540 which has Outer Foam 3530 disposed upon the upper surface of the Outer Track 3540.

[0206] Visible within the inner periphery of the Outer Foam 3530 is Inner Collar 3570 upon the upper edge of which is disposed an Inner Track 3510. Inner Foam 3520 is disposed upon the upper surface of the Inner Track 3510. The Inner Foam 3520 and Outer Foam 3530 are the surfaces of the PAD which engage against the user’s head and ear.

[0207] The profile of the Outer Collar 3550, Outer Track 3540 and Outer Foam 3530 on the right hand side of the PAD in Figure 35 has a profile which differs from that on the left hand side. This being a “dip” within profile to align with the cheek bone of a human user. Within other embodiments this “dip” may not be present.

[0208] Within the Inset within Figure 35 there is depicted a design of the retention of the Outer Track 3540 and Outer Foam 3530 onto the rim of the Outer Collar 3550 wherein a compressible O-ring 3580 is disposed between the top of the rim of the Outer Collar 3550 and the groove within the Outer Track 3540 and a Projection 3590 on the inside of the groove within the Outer Track 3540 engages with a groove on the wall of the Outer Collar 3550. In this manner the Outer Track 3540 is retained in position by friction and / or compression (between the Outer Track 3540 and Outer Collar 3550) and the projection wherein the Outer Track 3540 can be demountably attached and removed allowing replacement of the OuterTrack 3540 and Outer Foam 3550. A similar means may be employed to attached the Inner Track 3510 and Inner Foam 3520 to the Inner Collar 3570.

[0209] The internal construction of the PAD depicted in Figure 35 is evident within Figure 36 which presents a cross-sectional view. Accordingly, the Outer Hemisphere 3560 is visible with the Outer Collar 3550. These may be within embodiments of the invention formed from different materials which are joined together or be formed from the same material. Where they are formed from the same material whether the Outer Hemisphere 3560 and Outer Collar 3550 are formed as two piece-parts which are joined together or as a single piece-part will be a manufacturing process - cost based decision.

[0210] Attached around the rim of the Outer Collar 3550 is Outer Track 3540 which is depicted as comprising a slot on its lower side that engages the rim of the Outer Collar 3550 and a planar upper surface to which the Outer Foam 3530 is attached. The Outer Track 3540 within embodiments of the invention may be formed from a plastic to which a foam forming the Outer Foam 3530 is attached, for example via an adhesive. Alternatively, the Outer Foam 3530 may be a silicone, a rubber or other flexible material allowing the Outer Foam 3530 to conform or partly conform to the user’s head. The Outer Hemisphere 3560, Outer Collar 3550, Outer Track 3540 and Outer Foam 3530 form the outer cup of the PAD.

[0211] Disposed within the outer cup of the PAD is the inner cup. This comprises an Inner Collar 3570, which is closed at its lower end by Disk 3620 within which is disposed Acoustic Foam 3610, the Inner Foam 3520 and Inner Track 3520. Disposed between the Disk 3620 and the distal end of the Outer Hemisphere 3560 to the open end of the Inner Collar 3570 are Compressible Foam 3620 and first Retention Means 3640 which retains the Compressible Foam 3620 in position with respect to the Outer Hemisphere 3560. A second Retention Means 3650 retains the Disk 3620 in position against the other end of the Compressible Foam 3620 and thereby the other elements of the inner cup. Disposed on the exterior surface of the Outer Hemisphere 3560 are Finger Grips 3660 to aid holding or moving the PAD where no outer casing is disposed around the PAD.

[0212] It would be evident that the version of the PAD depicted in Figures 35 and 36 employs Collars that are 1.20 mm (approximately 0.047”) thick and a hemisphere and a circular disk that is approximately 1.0 mm (0.040”) thick. If both of these cups are stainless steel this results in a heavy headset. In order to decrease the mass of the PAD modifications may include, but not be limited, to making the outer cup out of thinner stainless steel, aluminum or a plastic as most of the mass comes from the outer cup. Embodiments using plastic may be simpler tomanufacture and less expensive. In these variants the inner cup may stay formed from stainless steel as it is smaller and contributes less to the overall mass of the headset.

[0213] Referring to Figure 37 there is depicted a plot of measured insertion loss versus frequency of a PAD according to an embodiment of the invention relative to two commercial headsets over the frequency range 100 Hz to 9,900 Hz. These measurements being performed on the inventor’s behalf by researchers at the National Research Centre (NRC) of Canada. The experimental set-up at NRC comprises an acoustic test fixture (GRAS 45CB Acoustic Test Fixture from GRAS Acoustics) which closely mimics a human as closely as possible, even being temperature controlled to 37°C the same as human skin.

[0214] First and second Plots 3710 and 3720 in Figure 37 respectively depict the insertion loss versus frequency of Apple™ Airpods™ with automatic noise cancelling (ANC) turned off and on wherein it is evident that the ANC primarily impacts performance below -1,700 Hz and actually slightly degrades performance between -1,700 Hz and 3,900 Hz. Third Plot 3730 depicts the performance of the 3M™ X5A earmuffs, considered one of the benchmarks for highest performing noise protection commercially available, where it is evident that these provide superior isolation relative to first and second Plots 3710 and 3720 respectively. Also depicted is the performance of a PAD according to an embodiment of the invention wherein below -800 Hz the performance is comparable to the 3M™ X5A in third Plot 3730 but above this provides improved isolation performance, typically in excess of 10 dB from -1, 500 Hz to 9,900 Hz.

[0215] Further developments may improve the low frequency performance of PADs according to embodiments of the invention or by adding ANC to the PAD with or without specific processing for these lower frequency components of exterior signals being attenuated. As evident with the large change between first and second Plots 3710 and 3720 with ANC off and on then these would indicate that the indicate that the addition of ANC to the exemplary PADs according to embodiments of the invention could significantly improve performance in the lower frequency region from approximately 1500Hz down. If a similar enhancement can be obtained then a PAD with ANC according to an embodiment of the invention would offer enhanced performance across the full frequency range from 100 Hz to 9,900 Hz against both commercial devices and would offer best in class performance for noise protection devices as well as far superior noise cancelling headphones.

[0216] Noise Reduction Rating (NRR) is a metric, common in the US for example, to evaluate hearing protection performance. It is calculated through human trial data at 9 frequencies, these being 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz, 3150Hz, 4000Hz, 6300Hz,and 8000Hz. High NRR scores are given to headsets with a high mean attenuation for each frequency tested and low standard deviation across the participants, meaning every participant demonstrates a similar mean attenuation to the other participants at each frequency. Because having a low standard deviation is critical to achieve a high NRR, the use of foam with its ability to accommodate large variations in head geometry is a suitable candidate for creating a seal against the head.

[0217] In practice and due to the nature of the NRR calculation, each of the 9 frequencies contribute unequally to the NRR. For example, assuming typical standard deviation values, the fourth Plot 3740 for a PAD according to an embodiment of the invention would have the performance at 125Hz, 250Hz, and 500Hz account for 67.2%, 4.9%, 24.8% of the contribution towards the NRR, respectively. The remaining 3.2% of the contribution to the NRR comes from the other 6 frequencies. Accordingly, to improve the NRR of a PAD according to an embodiment of the invention a primary focus is to improve the device’s performance at 125Hz and 500Hz, with the other frequencies having such high performance that they do not contribute significantly.

[0218] Figure 38 depicts the performance data collected for a variety of headsets at NRC. Accordingly, there are depicted first to fifth plots 3810 to 3850 comprising:• First Plot 3810 for an inner cup according to an embodiment of the invention only with standard foam gaskets sealing against the head of the dummy;• Second Plot 3820 for an outer cup according to an embodiment of the invention only with standard foam gaskets sealing against the head of the dummy;• Third Plot 3830 for combination of outer and inner cups according to embodiments of the invention with standard foam gaskets;• Fourth Plot 3840 for inner and outer cups according to embodiments of the invention with improved skin based sealing against the head of the dummy; and• Fifth Plot 3850 for commonly recognized highest performing commercially available hearing protection product (3M™ X5A).

[0219] Accordingly, if we review the results depicted in Figure 38 at 125Hz only, namely the leftmost point on the horizontal axis, then it is evident that for equivalent gaskets, having both the inner cup and an outer cup outperforms having either an inner cup or an outer cup only. For equivalent gaskets, the volume of the inner cup has little impact on the insertion loss but the addition of a higher quality seal via a skin on the foam improves the insertion loss significantly to approximately 20 dB. Accordingly, at 125Hz both inner and outer cups are desired alongside a high quality seal made possible with a skin on the gasket foam.

[0220] Now reviewing the results at 500 Hz then it is evident that for an increased volume of the innermost cup the insertion loss increases significantly. The volume of the individual cups shown from greatest to smallest are the prototype outer cup, the 3M™ X5A and the prototype inner cup. With equivalent gaskets, adding an outer cup on top of an inner cup makes only a small difference whilst the addition of a higher quality seal via a skin on the foam improves insertion loss. Accordingly, at 500Hz it would appear that an inner cup with a larger volume is desired alongside a high quality seal made possible with a skin on the gasket foam.

[0221] The underlying observation being that a larger inner cup would result in a superior NRR value is not surprising, as this is in line with the generic heuristic that with traditional single cup earmuffs, a greater cup volume is better for NRR performance as it lowers the resonant frequency of the inner cavity, creates a greater dislocation between the inner cup and the ear drum, allows for more porous fibrous material inside the inner cup etc. The volume of the inner cup could be increased via a number of ways including increasing its diameter, increasing its length, or by using a hemisphere rather than a circular disk at its end. The use of a hemisphere or hemisphere-like shape may make sense to employ in an inner or outer cup since it mimics a sphere, which provides the greatest volume possible with a given surface area.

[0222] Accordingly, further improvements in the results presented in Figure 38 for the prototype are projected by using higher quality seals through the use of a foam skin, for example, on both the outer cup and inner cup and by increasing the volume of its inner cup.

[0223] Whilst the measurements presented within Figures 37 and 38 were obtained with a standard acoustic dummy head such dummies do not exhibit “bone conduction” which occurs at approximately 2,000 Hz due to the underlying bones within the user’s skull. This phenomenon results in human skull conduction at approximately 2,000Hz which impacts audio device performance as at this frequency sound travels through the user’s forehead and skull, bypassing much of the design basis for hearing protection devices. As a result, the 2,000Hz performance for the NRR calculation makes a large contribution to the NRR overall, so this greatly limits how high of an NRR is possible.

[0224] Accordingly, skull conduction will result in sounds near and around 2,000Hz being conducted to the user’s aural canal regardless of what acoustic device is used. Accordingly, where a user is wearing a PAD to improve their concentration or help them sleep etc. and the PAD incorporates a loudspeaker then the PAD may generate white noise over a frequency range around 2,000 Hz to mask any external sound conducted to the user’s aural canal through bone conduction.

[0225] As noted above improving the sealing of the inner and outer cups against the head with thin Inner and Outer Foam respectively improves performance of the PAD. However, a tradeoff between thinner foam and adequate sealing across a defined population base exists. Further, the inventors noted that a moderate force is required to compress silicone if this is employed as these sealing elements even if it has a very low durometer (e.g. 00-10). Further, users generally want a headset with a low clamping force for comfort but a high quality seal has to be made across large variations in human head shape. However, a modified silicone structure may be employed as depicted in first Image 4000A in Figure 40 wherein a gasket that uses the same 00-10 silicone was made to “bend" rather than compress with an “arm” initially reaching out under a mechanical disadvantage. Whilst the initial design variant did not perform as well as the foam embodiments across all frequencies this design did perform better at 125Hz and 250Hz compared to the 3M™ X5A during NRR testing. Accordingly, variants of the design may provide enhanced performance comparable to those with foam or this design may support with variant PAD designs for a wider range of users or it may offer a lower cost PADs with reduced performance specifications. Such a variant being depicted in second Image 4000B wherein the silicone Gasket 4020 has Foam 4010 attached around it.

[0226] Within embodiments of the invention where a wireless earbud or hearing aid may be worn by the user wireless reception through the PAD may be poor. Accordingly, within embodiments of the invention an antenna pair may be provided, one internal to the PAD and another external to the PAD with interconnection such that wireless signals received by the external antenna are coupled to the internal antenna and therein to the wireless earbud / hearing aid.

[0227] Further, some earbuds / hearing aids have “stems: that extend parallel to the user’s head from the loudspeaker portion to house an antenna, electronics, battery etc. The design of PAD may establish a minimum inner dimension for the Inner Cup such that the Inner Cup does not contact the stem and dislodge the earbud / hearing aid. It would also be evident that the requirement to accommodate earbuds / hearing aids also establishes a minimum distance for the Acoustic Foam 3610 relative to the user’s head to accommodate the additional depth of the earbud / hearing aid.

[0228] Within the embodiments according to the embodiment of the invention a material such as silicone may be best for improved STL performance. However, this material is not that complaint and accordingly it is difficult to establish a design that struggles to achieve a quality seal against a wide range of human head variations. Accordingly, embodiments of the inventiondescribed within this specification employ a foam which whilst providing reduced STL performance provides an improved seal against a wider range of head geometries.

[0229] However, within other embodiments of the invention thermosetting material may be employed to form the gasket rather than a foam. Accordingly, a PAD may be sold or provided to a user with a gasket which can be heated and brought into contact with the user’s head wherein upon cooling it takes the shape of the user’s head. Depending upon the materials of the PAD the gasket may be heated whilst still attached such that no additional handling of the gasket prior to attachment and shaping is undertaken. Within another embodiment of the invention the gasket may be provided with a tab such that it can be heated and held without the user touching the gasket and attaching it to the PAD for shaping.

[0230] It would be evident that whilst the description above relates to discrete PADs and / or PADs forming part of headsets that PADs according to embodiments of the invention may be integrated into hard hats, military helmets, aviation helmets etc.

[0231] Within embodiments of the invention a PAD may be employed in conjunction with a pair of glasses, for example prescription glasses or sunglasses of the user or eye protection. Whilst for protection applications it may be appropriate to have eye protection that is attached to the PADs either side of the user’s head this does not work for prescription glasses or sunglasses. Accordingly, the design of the Outer Foam and / or Outer Track and possibly Outer Collar may be modified to provide increased space around the temple to proximal the user’s hear such that the PAD sits over the arm of the frame of the glasses. Other configurations including a “slit” in the outer cup foam where the glasses arm can slip through may be employed but increase complexity and potential user dissatisfaction as simply putting and taking of the PADs is now a little more complex.

[0232] Within embodiments of the invention described above where a porous-fibrous material is desired between the inner and outer cups for performance then it can be difficult to fill the complex volume between the cups with sheets of foam etc. Accordingly, within embodiments of the invention this material may be injected through a small opening in the outer cup so that the insulation fills this space as a liquid would. A membrane between the outer and inner cups may be employed to limit flow of the injected material past a defined point towards the opening between the inner and outer cups.

[0233] Within embodiments of the invention an inner cup or outer cup may comprise a micro-perforated panel where the holes offer significant STL at and around a certain frequency which may be a means of improving low frequency STL for example.

[0234] Whilst the inventor has established sound attenuating PADs without exploiting damping, other embodiments of the invention may employ damping structures to eliminate potential resonances or frequency dependent interactions in the inner and outer cups etc. For example, one design may exploit a matrix of strips in a spider-web like structure whilst another a sheet without openings or a sheet with a defined pattern of openings. This provides damping whilst consuming less of the mass budget and introducing less of an impedance matching risk to the STL performance since much of the surface area is left not covered with a damping material. Optionally, different thickness strips may be employed, for example 2.5mm and 1.27mm thick strips. A damping spray may also be employed.

[0235] Within embodiments of the invention the designs have been presented with respect to sound attenuating headsets employing PADs comprising an inner cup and outer cup, i.e. these provide two walls between the exterior environment and the user’s ear canal. However, it would be evident that within other embodiments of the invention that one or more additional walls may be employed. Where the one or more additional walls or cups are added within a given set of design constraints, e.g. with mass budget and aesthetic constraints the wall gap between walls will reduce and have an impact on the STL, generally reducing it. However, it would be evident that a third wall, cup or body may be for example deployed around the outer cup to change the visual profile of the individual PADs away from hemispherical, ellipsoidal etc. In this manner the third wall may be viewed as decorative and hence may be formed from other materials than the cups where the primary considerations are low weight, formable to desired geometry, etc. and offering different colours, surface finishes, marking etc.

[0236] Within embodiments of the invention the designs have been presented with respect to sound attenuating headsets employing PADs comprising an inner cup and outer cup, i.e. these provide two walls between the exterior environment and the user’s ear canal. However, within other embodiments of the invention, a PAD may comprise a single cup or wall which may comprise a solid wall, a laminated wall, stiffness driven wall, a mass driven wall, a membrane based wall or another wall or a combination of such wall according to embodiments of the invention as described and depicted within this specification. However, it would be evident that a further wall, cup or body may be deployed around this cup to change the visual profile of the individual PAD away from hemispherical, ellipsoidal etc. In this manner the further wall may be viewed as decorative and hence may be formed from other materials than the cup where the primary considerations are low weight, formable to desired geometry, etc. and offering different colours, surface finishes, marking etc.

[0237] Within embodiments of the invention the material for a cup may be a solid material, a laminated material or a matrix comprising one or more materials disposed within a body formed from one or more other materials.

[0238] Within embodiments of the invention the inner cup and outer cup may have walls that are non-parallel / non-equidistant. Further, within embodiments of the invention the inner cup may be centered with respect to the outer cup or it may be disposed in a non-symmetric relationship to the outer cup in one or more axes.

[0239] Within embodiments of the invention in addition to a dislocation between the inner cup and the outer cup there may also be a dislocation between a headband and the outer cup. Accordingly, the Mounting disclosed and discussed within Figures 17 and 20 may be modified to a soft / loose / dislocated connection between the headband and the outer cup. For example, soft TPE could be used as the dislocating element. Such variants would allow the outer cup to move freely as a body and absorb sound energy as it moves due to the sound waves propagating through it. A soft or dislocated connection may also allow the headband to free rotate in three axes. Further, within embodiments of the invention a headband may be employed that does not touch the user’s head at all allowing the headband to move freely and be dislocated from the head. Within other embodiments of the invention the headband may have a damping material added or may employ a cushion that touches the head which is formed from a material with high damping such as TPE for example.

[0240] Within embodiments of the invention a material employed as the solid material, part of a laminated material or within the matrix may comprise a metal. The metal can provide high specific acoustic impedance, high density and high specific Young’s modulus as these all can lead to high STL in the assembled PAD. The metal may, for example, be selected from the group comprising copper, lead, platinum, tungsten, molybdenum, titanium, aluminum, nickel, magnesium, zinc, tin, lead, iron, tantalum, ruthenium, chromium, cobalt, carbon, and vanadium.

[0241] Within embodiments of the invention a material employed as the solid material, part of a laminated material or within the matrix may comprise an alloy. The alloy can provide high specific acoustic impedance, high density and high specific Young’s modulus as these all can lead to high STL in the assembled PAD. The alloy may, for example, be selected from the group comprising Inconel™ (nickel-chrome alloys), steel, stainless steel, tungsten carbide, Monel™ (nickel-copper alloys), brass (copper-zinc alloys), bronze (copper-tin alloys) and manganese steel.

[0242] Within embodiments of the invention a material employed as the solid material, part of a laminated material or within the matrix may comprise a ceramic. The ceramic can provide high specific acoustic impedance, high density and high specific Young’s modulus as these all can lead to high STL in the assembled PAD. The ceramic may, for example, be selected from the group comprising alumina, silicon carbide, a glass, zirconia, titanium dioxide, boron nitride, silicon nitride, a porcelain, a glass ceramic and magnesium oxide.

[0243] Within embodiments of the invention a material employed as the solid material, part of a laminated material or within the matrix may comprise a polymer or plastic. The polymer or plastic can provide high specific acoustic impedance, high density and high specific Young’s modulus as these can all lead to high STL in the assembled PAD. The polymer or plastic may, for example be selected from the group comprising polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polytetrafluoroethylene (PTFE), a polyamide (e.g. nylon), polyurethane (PU), polyethylene terephthalate (PET), poly(methyl methacrylate) (PMMA, e.g. acrylic), ethylene-vinyl acetate (EVA), polyoxymethylene (POM), polyimide (PI), polylactic acid (PLA), a polyhydroxyalkanoate (PHA), polybutylene terephthalate (PBT), low density polyethylene (LDPE), high density polyethylene (HDPE), polyether ether ketone (PEEK) and EPDM rubber.

[0244] Within embodiments of the invention a material employed as the solid material, part of a laminated material or within the matrix may comprise a composite. The composite can provide high specific acoustic impedance, high density and high specific Young’s modulus as these can all lead to high STL in the assembled PAD. The composite may, for example, be selected from the group comprising carbon fiber, fiberglass, Kevlar™, concrete, plywood, a metal matrix composite, and a wood plastic composite.

[0245] Within embodiments of the invention a material employed as the solid material, part of a laminated material or within the matrix may comprise a natural material. The natural material can provide high specific acoustic impedance, high density and high specific Young’s modulus as these can all lead to high STL in the assembled PAD. The natural material may, for example, be selected from the group comprising a wood, a natural rubber and bamboo.

[0246] Within embodiments of the invention a material employed as the solid material, part of a laminated material or within the matrix may comprise a group 4 material. The group 4 material can provide high specific acoustic impedance, high density and high specific Young’s modulus as these can all lead to high STL in the assembled PAD. The group 4 material may, for example, be selected from the group comprising silicon, graphite and graphene.

[0247] Within the designs presented according to embodiments of the invention the inner and outer cups of the PAD are described as being “dislocated” by which the inventor means that the connection between the inner and outer cup (or any adjacent cups within a sequence of cups) are mechanically connected by elastic or low Young’s modulus materials so that there is only weak or low mechanical coupling from one cup to another. Within embodiments of the invention the inner cup may be supported by air or another fluid, i.e. it floats, or it may be suspended by elastic elements or magnetically floating as the outer cup and inner cup are permanently or electromagnetically magnetized with the same polarity.

[0248] Within embodiments of the invention as described with respect to Figures 12, 13 and 16 the space between cups is air except for Foam 1230 and Foam 1330 respectively and the Gasket of which Membrane 1640 connects between the cups. Within other embodiments of the invention this space between cups may be filled with a low density (for low mass contribution) material such as a foam, a low density or porous rubber or a porous fibrous material. This porous fibrous material may be mineral wool, rock wool, fiberglass matting (similar to fiberglass insulation) or jute fibers which may help with high frequency STL.

[0249] These form one subset of design options for dislocating one cup from another. These may include, but not be limited to, mechanical springs, pneumatic springs, or gas springs or leaf springs, elastic or low Young’s modulus linkages such as elasticated cords or bands -cables etc., shock absorbers such as hydraulic or pneumatic shocks and a low durometer silicone or TPE.

[0250] Optionally, an alternate suspension / dislocation approach for one cup with respect to another is to exploit magnetic elements as a portion of the cups such that an inner cup is magnetically “suspended” within another with a magnetic force, e.g. repulsion, or it can also be employed to resist motion of the inner cup away from the user’s head into the outer cup for example.

[0251] Optionally, an alternate suspension / dislocation approach for one cup with respect to another is to employ a balloon that fills the cavity between the pair of cups such that movement of the inner cup is cushioned by the balloon. Optionally, the balloon may be a plurality of balloons or a plurality of balloons in sheet form such as commonly known bubble wrap for example. Within other embodiments of the invention the balloons may be filled with air or with a fluid other than air such as helium, nitrogen, argon, a silicone oil, a perfluorocarbon (PFC), a mineral oil, water and glycerin for example.

[0252] Optionally, the fluid may be pressurized relative to atmospheric pressure, at atmospheric pressure or be below atmospheric pressure. Optionally, it may be at constant pressure or the pressure may be adjusted by a mechanical, electrical, or manual means.

[0253] Within embodiments of the invention the gasket around the inner cup may be profiled such that under a defined buildup of pressure a channel opens from the region around the user’ s ear to the exterior environment to relieve pressure around the user’s ear drum.

[0254] Apart from the consideration of active noise canceling and the potential inclusion of a loudspeaker in the discussion above with respect to sound protecting headsets, the above has been presented from the perspective of passive headsets. However, it would be evident that optionally additional elements including wireless interfaces, wired interfaces, sensors, microphones for communication etc. may be integrated into the headsets such that the headset can receive electronic data from or provide other electronic data to one or more external sources or recipients such as SOCNETS 165, first and second Service Providers 170A and 170B respectively, first and second Third Party Service Providers 170C and 170D respectively, a User 170E, first and second Enterprises 175A and 175B respectively, first and second Organizations 175C and 175D respectively, and a Government Entity 175E as depicted in Figure 1 where the wireless or wired interface of the headset connects to a Network 100.

[0255] With a PAD according to embodiments of the invention designed to provide high STL then it would be evident that if a user were employing such a PAD with an ear-bud that includes a microphone in conjunction with a loudspeaker that the microphone would not be able to pick up the user’s voice due to the inherent high STL of the PAD. Accordingly, one or more microphones externally disposed on the PAD may be employed to allow the user to record audio, make or receive a telephone call etc. Alternatively, a stand-alone microphone may be employed in conjunction with a PAD.

[0256] The foregoing disclosure of the exemplary embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents.

[0257] Further, in describing representative embodiments of the present invention, the specification may have presented the method and / or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited tothe particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be constmed as limitations on the claims. In addition, the claims directed to the method and / or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.

Claims

CLAIMSWhat is claimed is:

1. A personal acoustic device comprising:an outer cup having a defined geometry and an opening;an inner cup having another defined geometry and another opening where a portion of the inner cup is disposed within the outer cup; andone or more elements at least one of locating, retaining and limiting motion of the inner cup with respect to the outer cup; whereinthe inner cup fits over a defined portion of the user’s ear.

2. The personal acoustic device according to claim 1, whereinthe defined geometry is a defined portion of a sphere of a first diameter;the another defined geometry is one of a defined portion of a sphere of a second diameter and a cylinder of a third diameter and first length which is closed at one end; and the opening and another opening are on a same side of the device.

3. The personal acoustic device according to claim 1, whereinthe defined geometry is a defined portion of an ellipsoid with a first major axis and a first minor axis; andthe another defined geometry is a defined portion of another ellipsoid with a second major axis and a second minor axis.

4. The personal acoustic device according to claim 1, whereinthe one or more elements comprise at least one:a gasket fitting to the opening of the outer cup and the another opening of the inner cup with a membrane of a defined material and defined thickness;a soft element disposed between an end of the inner cup distal to the opening and an end of the outer cup distal to the opening of the outer cup; and one or more elements of low Young’s modulus disposed between the outer surface of the inner cup and an inner surface of the outer cup.

5. The personal acoustic device according to claim 1, whereina wall of the inner cup is at least one of a stiffness driven wall and a mass driven wall; and a wall of the outer cup is at least one of another mass driven wall and another stiffness driven wall.

6. The personal acoustic device according to claim 1, whereinthe one or more elements at least one of locating, retaining and limiting motion of the inner cup with respect to the outer cup comprises a foam element attached at one end to a portion of an outer surface of the inner cup distal to the another opening and at another distal end to an inner surface of the outer cup distal to the opening.

7. The personal acoustic device according to claim 1, whereina rim of the outer cup around the opening has disposed upon it an element comprising at least one of a foam element and a flexible gasket; anda rim of the inner cup around the another opening has disposed upon it another element comprising at least one of another foam element and another flexible gasket.

8. The personal acoustic device according to claim 1, whereinat least one of the inner cup and the outer cup is either comprised of a number of laminated sheets of material and a number of membranes where the membranes are spaced apart from one another.

9. The personal acoustic device according to claim 1, whereina rim of the outer cup around the opening has a portion further away from the user’s head than the remainder of the rim of the outer cup; andthe portion is positioned such that upon a user placing the personal acoustic device against their ear the portion is proximate a temple of the user.

10. A personal acoustic device comprising:a band for fitting to a portion of a user comprising a personal acoustic device for attenuating sound to an ear of the user over a frequency range of interest; whereinthe personal acoustic device comprises:an outer cup having a defined geometry and an opening;an inner cup having another defined geometry and another opening where a portion of the inner cup is disposed within the outer cup; andone or more elements at least one of locating, retaining and limiting motion of the inner cup with respect to the outer cup; andthe inner cup fits over a defined portion of the user’s ear.

11. The personal acoustic device according to claim 10, whereinthe defined geometry is a defined portion of a sphere of a first diameter;the another defined geometry is one of a defined portion of a sphere of a second diameter and a cylinder of a third diameter and first length which is closed at an end distal to the another opening; andthe opening and another opening on a same side of the device.

12. The personal acoustic device according to claim 10, whereinthe defined geometry is a defined portion of an ellipsoid with a first major axis and a first minor axis; andthe another defined geometry is one of a defined portion of another ellipsoid with a second major axis and a second minor axis and a cylinder of a third diameter and first length which is closed at an end distal to the another opening; andthe opening and another opening on a same side of the device.

13. The personal acoustic device according to claim 10, whereinthe one or more elements comprise at least one:a gasket fitting to the opening of the outer cup and the another opening of the inner cup with a membrane of a defined material and defined thickness;a foam element disposed between an end of the inner cup distal to the opening and an end of the outer cup distal to the opening of the outer cup; and one or more elements of low Young’s modulus disposed between the outer surface of the inner cup and an inner surface of the outer cup.

14. The personal acoustic device according to claim 10, whereina wall of the inner cup is at least one of a stiffness driven wall and a mass driven wall; and a wall of the outer cup is at least one of another stiffness driven wall and another mass driven wall.

15. The personal acoustic device according to claim 10, whereinthe one or more elements at least one of locating, retaining and limiting motion of the inner cup with respect to the outer cup comprises a foam element attached at one end to a portion of an outer surface of the inner cup distal to the another opening and at another distal end to an inner surface of the outer cup distal to the opening.

16. The personal acoustic device according to claim 10, whereina rim of the outer cup around the opening has disposed upon it an element comprising at least one of a foam element and a flexible gasket; anda rim of the inner cup around the another opening has disposed upon it another element comprising at least one of another foam element and another flexible gasket.

17. The personal acoustic device according to claim 10, whereinat least one of the inner cup and the outer cup is either comprised of a number of laminated sheets of material and a number of membranes where the membranes are spaced apart from one another.

18. The personal acoustic device according to claim 10, whereina rim of the outer cup around the opening has a portion further away from the user’s head than the remainder of the rim of the outer cup; andthe portion is positioned such that upon a user placing the personal acoustic device against their ear the portion is proximate a temple of the user.

Images