System and method for generating an audio signal

Abstract

Techniques described herein generally relate to generating an audio signal with a speaker. In some examples, a speaker device is described that includes a membrane and a shutter. The membrane may be configured to be along a first directional path and at least one frequency oscillation effective to generate an ultrasonic acoustic signal. The shutter is positioned along the propagation of the ultrasonic acoustic signal and is configured to modulate the ultrasonic acoustic signal such that an audio signal is generated.

Description

[0001] This application is a divisional application, and its original application is a patent application submitted to the Chinese Patent Office on March 24, 2022, with the application number 202080067113.7 and the invention title "Systems and Methods for Generating Audio Signals". Technical Field

[0002] Generally speaking, the present disclosure relates to systems and methods for generating audio signals. In some examples, the systems and methods for generating audio signals are applied in mobile, wearable or portable devices. In other examples, the systems and methods for generating audio signals are applied to headphones, headsets, hearables or hearing aids. Background Art

[0003] US 8861752 describes a picospeaker (which is a novel sound generation device) and a method for sound generation. The picospeaker creates an audio signal by generating an ultrasonic sound beam that is subsequently actively modulated. The resulting modulated ultrasonic signal has a lower audio frequency sideband, which corresponds to the frequency difference between the frequency of the ultrasonic sound beam and the modulation frequency. US 20160360320 and US20160360321 describe MEMS architectures for implementing picospeakers. US20160277838 describes a method for implementing a picospeaker using MEMS processing. US2016277845 describes an alternative method for implementing a picospeaker using MEMS processing.

[0004] The existing technical methods for implementing picospeakers are complex and require many processing steps. Therefore, there is a desire to provide an architecture and implementation method that reduce complexity and the number of processing steps.

[0005] Vocabulary

[0006] "Acoustic signal" - as used in the present disclosure, refers to a mechanical wave that passes through a gas, liquid or solid medium at any frequency or spectral portion between 10 Hz and 10,000,000 Hz.

[0007] "Audio" or "audio spectrum" or "audio signal" - as used in the present disclosure, refers to an acoustic signal or a portion of an acoustic signal having a frequency or spectral portion between 10 Hz and 20,000 Hz.

[0008] "Speaker" or "picospeaker" or "micro speaker" or "nanospeaker" - as used in the present disclosure, refers to a device configured to generate an acoustic signal, wherein at least a portion of the signal is in the audio spectrum.

[0009] "membrane" - as used in the present disclosure, refers to a flexible structure constrained by at least two points.

[0010] "blind" - as used in the present disclosure, refers to a structure having at least one acoustic port through which sound waves pass with low loss.

[0011] "shutter" - as used in the present disclosure, refers to a structure configured to move relative to the blind and increase the acoustic loss of one or more acoustic ports.

[0012] "acoustic medium" - as used in the present disclosure, refers to any one of the following, but is not limited to the following: a bounded region in which a material is contained in an enclosed acoustic cavity; an unbounded region in which a material is characterized by the speed of sound and is unbounded in at least one dimension. Examples of acoustic media include, but are not limited to: air; water; the ear canal; the enclosed volume around the ear; air in free space; air in a duct or other acoustic channel. SUMMARY OF THE INVENTION

[0013] Some embodiments of the present disclosure may generally relate to a loudspeaker device that includes a membrane and a shutter. The membrane is positioned in a first plane and is configured to oscillate along a first direction path and at a first frequency effective to generate an ultrasonic acoustic signal. The shutter is located in a second plane substantially spaced apart from the first plane. The shutter is configured to modulate the ultrasonic acoustic signal to generate an audio signal.

[0014] Other embodiments of the present disclosure may generally relate to a loudspeaker device that includes an array composed of a membrane and a shutter. The array composed of the membrane and the shutter operates independently or is driven by a common source. Examples of drive signals include, but are not limited to: pulse width modulation and modulated sine signals. The drive unit is a semiconductor integrated circuit that includes: a communication unit; a charge pump configured to generate a high voltage signal; a switching unit configured to modulate the high voltage signal. The drive unit receives a digital sound data stream and a working voltage and outputs drive signals for the membrane and the shutter. In some embodiments, the membrane and the shutter operate asynchronously and / or independently of each other at one or more frequencies. In other embodiments, the membrane and the shutter operate synchronously at the same frequency. In the synchronous operation mode, the amplitude of the audio signal is controlled by any one of the following, but is not limited to the following: the relative phase of the membrane and shutter operations; the amplitude of the shutter operation; the amplitude of the membrane operation; any combination of these.

[0015] The foregoing summary is illustrative only and is not intended to be limiting in any way. Additional aspects, embodiments, and features will become apparent from the following detailed description and the accompanying drawings, in reference to the foregoing illustrative aspects, embodiments, and features. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The foregoing and other features of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings and the appended claims. It is to be understood that these drawings depict only several embodiments in accordance with the present disclosure and are, therefore, not to be considered limiting of its scope, and the present disclosure will be described with additional specificity and detail by use of the drawings.

[0017] Figure 1A is an example of a side view of a prior art architecture for a MEMS micro speaker unit;

[0018] Figure 1B is an example of a top view of a matrix arrangement of multiple units adapted from US2016277845;

[0019] Figure 2 is an example of a top view of a micro speaker unit with a simplified process flow;

[0020] Figures 3A - 3D is an example of a simplified process flow for manufacturing a micro speaker;

[0021] Figures 4A - 4C is an alternative example of a simplified process flow for manufacturing a micro speaker;

[0022] Figure 5A is an alternative example of a mask for a single unit defining a membrane layer mask;

[0023] Figure 5B is an alternative example of a mask for a single unit defining a baffle layer mask that includes an aperture for acoustic power transmission;

[0024] Figure 5C is an alternative example of a mask for a single unit defining a shutter layer mask that includes an aperture for acoustic power transmission;

[0025] Figure 5D is an example of a 3×4 unit array of a device fabricated from a previous mask layer;

[0026] Figure 5E is an example of a 15×20 array of a MEMS speaker device fabricated from units of a previous mask layer;

[0027] Figure 6A is an example of a modified micro speaker including a backside hole;

[0028] Figure 6B is an alternative example of a pico speaker unit having a dorsal hole and an additional reference layer;

[0029] Figure 7 is an example of a PWM signal, where the signal has two voltage values and a variable pulse width;

[0030] Figure 8 is a conversion method from a(t) to the pulse width;

[0031] Figure 9A is an example of a method for operating a pico speaker.

[0032] Figure 9B is an example of a method for implementing a drive shutter and a membrane block;

[0033] Figure 10 is an example of a drive device connected to a pico speaker and providing an actuation signal to a membrane layer and a shutter layer;

[0034] Figure 11A is an alternative example of a schematic representation of a pico speaker unit;

[0035] Figure 11B is another example of a schematic representation of a pico speaker unit; and

[0036] Figure 11C is an example of a pico speaker unit having an overlay in the dashed line indicating the sound source position; a time-varying acoustic coupler; and an acoustic medium. Detailed Description

[0037] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, like symbols generally identify like components, unless the context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other examples may be used and other changes may be made without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein and shown in the figures, can be arranged, substituted, combined, and designed in a variety of different configurations, all of which are explicitly contemplated and form a part of the present disclosure. The present disclosure particularly relates to methods, devices, computer programs, and systems for generating audio signals.

[0038] In some examples, a loudspeaker device is described that includes a membrane and a shutter. The membrane is configured to oscillate along a first direction path and with a frequency combination that has at least one frequency that effectively generates an ultrasonic acoustic signal. The shutter and baffle are located near the membrane. In one non-limiting example, the membrane, baffle, and shutter can be positioned with a substantially parallel orientation relative to each other. In other examples, the membrane, baffle, and shutter can be positioned in the same plane, and the acoustic signal is transmitted along an acoustic channel leading from the membrane to the shutter. In another example, the modulator and / or shutter consists of more than one part.

[0039] In some embodiments, the membrane is driven by an electrical signal that oscillates at a frequency Ω and thus moves as bCos(2π*Ωt), where b is the amplitude of the membrane movement and t is time. The electrical signal is further modulated by a part derived from the audio signal a(t). The characteristics of the acoustic signal are:

[0040] s(t)= b a(t)Cos(2π*Ωt) (1)

[0041] Applying the Fourier transform to equation (1) gives the frequency domain representation

[0042] S(f)= b / 2 * [A(f-Ω)+ A(f+Ω)] (2)

[0043] where A(f) is the spectrum of the audio signal. Equation (2) describes a signal with an upper sideband and a lower sideband near the Ω carrier frequency. Applying the acoustic signal of equation (1) to an acoustic modulator operating at a frequency Ω gives

[0044] S(t)= b a(t)Cos(2π*Ωt) (l +m Cos(2π*Ωt) ) (3)

[0045] where l is the loss of the modulator and m is the modulation function and l + m < 1 due to energy conservation. In the frequency domain

[0046] S’(f)=b / 4 * [m A(f)+ m A(f+2Ω)+ A(f-Ω)+ A(f+Ω)] (4)

[0047] where b / 4*m A(f) is the audio signal. The remaining terms are ultrasonic signals, where m A(f+2Ω) is twice the modulation frequency, and A(f-Ω)+A(f+Ω) is the original unmodulated signal. Additional acoustic signals can occur due to any one of but not limited to the following: ultrasonic signals from shutter movement; intermodulation signals due to the nonlinearity of the acoustic medium; intermodulation signals due to other nonlinear sources (including electrical and mechanical).

[0048] In another example, an audio signal is enhanced by the acoustic radiation pressure of an ultrasonic signal. This is a new method of audio generation, in which an audio system generates an ultrasonic signal. The ultrasonic signal exerts a radiation force on the surface it impinges on, including the eardrum (tympanic membrane). By modulating the ultrasonic signal, the amplitude of the radiation force can be changed, thereby affecting the mechanical movement of the eardrum, which is recorded as sound by the ear (and the brain). The radiation pressure of the acoustic signal is well documented and given as

[0049]

[0050] where P is the radiation pressure, and where E, p, ρ, c are the energy density of the acoustic beam near the surface, the acoustic pressure, the density of the acoustic medium, and the speed of sound, respectively. α is a constant related to the reflection characteristics of the surface. If all the acoustic energy is absorbed on the surface, α equals 1, while for a surface that reflects all the acoustic energy, α is 2. The acoustic power E carried by the beam is E = W / c, where W is the power density of the transducer. In one example, to produce an audio sensation at the eardrum, the ultrasonic signal is modulated with an audio signal. The audio signal causes changes in the acoustic radiation force, which are recorded as an audio signal by the ear. In a non-limiting example, the audio is AM modulated on the ultrasonic carrier

[0051] S(t) = Cos(2π*Ωt) (l + m a(t) ) (6)

[0052] E is proportional to m a(t), and the change in the radiation force P is proportional to m a(t), resulting in movement of the eardrum proportional to m a(t). Thus, an ultrasonic loudspeaker can produce sound using any one or both of the above methods. In one example, these methods are used intermittently, in another example, these methods are used simultaneously, and in another example, only modulation or only the radiation force is used.

[0053] Figure 1AAn example of a side view of a prior art architecture for a MEMS micro-speaker unit (121). The micro-speaker unit consists of at least three layers. A membrane (105) that generates the acoustic signal described in Equation (1) by moving in the direction of arrow (190). A baffle (103) and a shutter (101) that move relative to each other and modulate the acoustic signal, as described in Equation (3). In one example, a driving device (109) provides a voltage signal to the membrane (15) and a second voltage signal to the shutter (101), and sets the voltage to the baffle (103) to zero or ground. The first and second voltage signals respectively provide the driving forces for generating the acoustic sound of Equation (1) and the modulation function of Equation (3). In an additional example, a fourth layer; a handle (107) is included. The driving device (109) is electrically connected to a digital audio source via line (119), to a low voltage source via line (121), to the membrane layer (105) via line (115), to the baffle layer (103) via line (117), and to the shutter layer (101) via line (113). The micro-speaker device consists of a plurality of micro-speaker units (121). Figure 1B An example of a top view of a matrix arrangement of a plurality of units (121) adapted from US2016277845. The units (121) are electrically connected in parallel such that a first driving voltage is applied to all the membranes (Figure 1A 105) in the connected units (121), and a second driving voltage is applied to all the shutters ( Figure 1A 101) in the connected units (121).

[0054] Figure 2 An example of a top view of a micro-speaker unit with a simplified process flow. The shutter layer (201) is visible. The shutter layer (201) and the baffle layer ( Figure 1A 103) have non-overlapping apertures (211, 213). The apertures provide a route for the acoustic beam generated by the membrane ( Figure 1A , 105). When the shutter layer (201) is pulled towards the baffle layer, the acoustic route is blocked and the acoustic signal is attenuated. When the shutter layer (201) is released, the distance between the shutter layer (201) and the baffle layer ( Figure 1A 103) increases, the acoustic signal route is not blocked, and the acoustic signal is not attenuated.

[0055] Figures 3A - 3D An example of a simplified process flow for manufacturing a micro-speaker. Figure 3AAn example of a side view of a micro speaker unit during manufacturing after patterning a membrane layer (301). The micro speaker unit consists of a silicon wafer (350), a first dielectric layer (311), and a patterned membrane layer (301). The first dielectric layer is deposited on the silicon wafer. The membrane layer is deposited on the first dielectric layer (311). The membrane layer is coated with a photoresist material. The photoresist is exposed and developed using a first mask (331) such that the photoresist has the same pattern as the first mask (331). The membrane layer is etched through the developed photoresist and the first mask pattern is transferred to the membrane layer (Figure 1, 107), thereby creating the patterned membrane layer (301). In one example, a process that does not etch the dielectric layer is used to etch the membrane layer. In an alternative example, the dielectric is etched but then covered during the deposition of the next layer. In another example, a thin layer of dielectric is deposited before depositing the membrane layer. Examples of the thickness include but are not limited to 100 nm, 200 nm, or less than 300 nm. The thin dielectric layer provides additional protection to the sacrificial layer during removal of the mask material. In another example, the thickness of the first dielectric layer (311) is any of the following, but not limited to: 1 micron; 2 microns; 3 microns; 4 microns; 1 - 5 microns.

[0056] Figure 3BAn example of a side view of a MEMS speaker unit during manufacturing after patterning the baffle layer (303). A second dielectric layer (313) is deposited on the patterned membrane layer (301). In some examples, the surface flatness of the second dielectric layer is enhanced by any one or combination of the following methods: Chemical Mechanical Polishing (CMP); heated reflow; chemical etching; chemical reflow. The baffle layer is deposited on the second dielectric layer (313). The baffle layer is coated with a photoresist material. The photoresist is exposed and developed using a second mask (333) such that the photoresist has the same pattern as the second mask (333). The membrane layer is etched through the developed photoresist, and the first mask pattern is transferred to the photoresist. The baffle layer is etched through the exposed photoresist, and the second mask pattern is transferred to the baffle layer (Figure 1, 105), resulting in a patterned baffle layer (303). In one example, a process that does not etch the dielectric layer is used to etch the membrane layer. In an alternative example, the dielectric is etched but then covered during the deposition of the next layer. In another example, a thin layer of dielectric is deposited before depositing the membrane layer. Examples of the thickness include but are not limited to 100 nm, 200 nm, or less than 300 nm. During removal of the mask material, the thin dielectric layer provides additional protection for the sacrificial layer. In another example, the thickness of the second dielectric layer (313) is any one of the following, but not limited to the following: 4 microns; 5 microns; 1 - 5 microns, 5 - 10 microns; 10 - 20 microns; 20 - 40 microns; less than 50 microns.

[0057] Figure 3CAn example of a side view of a micro speaker unit during manufacturing after patterning the shutter layer (305). A third dielectric layer (315) is deposited on the patterned baffle layer (303). In some examples, the surface flatness of the second dielectric layer is enhanced by any one or combination of the following methods: chemical mechanical polishing (CMP); thermal reflow; chemical etching; chemical reflow. The shutter layer is deposited on the third dielectric layer (315). The shutter layer is coated with a photoresist material. The photoresist is exposed and developed using a third mask (335) such that the photoresist has the same pattern as the third mask (335). The film layer is etched through the developed photoresist, and the third mask pattern is transferred to the photoresist. The shutter layer is etched through the exposed photoresist, and the third mask pattern is transferred to the shutter layer (FIG. 1, 103), thereby creating the patterned shutter layer (305). In one example, a process that does not etch the dielectric layer is used to etch the film layer. In an alternative example, the dielectric is etched but then covered during the deposition of the next layer. In another example, a thin layer of dielectric is deposited before depositing the film layer. Examples of the thickness include but are not limited to 100 nm, 200 nm, or less than 300 nm. The thin dielectric layer provides additional protection to the sacrificial layer during removal of the mask material. In another example, the thickness of the third dielectric layer (315) is any one of the following, but not limited to: 2 microns; 3 microns; 4 microns; 5 microns; 1 - 5 microns, 5 - 10 microns.

[0058] Figure 3D An example of a side view of a micro speaker unit during manufacturing after releasing the film (301), baffle (303), and shutter (305) layers. The release of the layers is facilitated by an etching process that partially removes the first (311), second (313), and third (315) dielectric layers (especially under the membrane structure) and effectively releases at least a portion of the membrane (301), baffle (303), or shutter (305) structure. The membrane (301), baffle (303), and shutter (305) layers include apertures. The apertures provide a path for the acoustic signal to leave the structure. In one example, the apertures partially overlap. The overlap defines a modulated acoustic cavity. In Figure 3D which, an example of the overlap is shown by the distance between the dashed line (321) and the dashed line (323) or between the dashed line (325) and the dashed line (327). In one example, the overlap is constant. In another example, the overlap depends on the distance of the aperture from the center of the device. Thus, the overlap is given by O(r), where O is a function in microns and r is the distance of the aperture from the center of the device. In some examples, the overlap is any one of the following, but not limited to: 5 microns; 10 microns; 15 microns; 5 - 10 microns; 10 - 20 microns; less than 25 microns. In another example and with reference to Figure 2, the shutter layer includes a central orifice (215) and an outer orifice (211). The overlap of the central orifice, i.e., the distance from the end of the central orifice (215) to the start of the baffle orifice (213) is denoted as o1 and can be any one of the following, but is not limited to the following: 5 - 10 microns; 10 - 20 microns. The overlap of the outer orifice (211) and the baffle orifice (213) is denoted as o2, is a function of distance and can be any one of 10 - 40 microns; a*o1, where a can be any one of the following, but is not limited to the following: 1; 1 - 2; 2 - 4. There is a relationship between the overlap and the shutter or baffle displacement, which has been described previously. For a given displacement, the overlap increases the modulation but also increases the loss. The optimization of the design includes identifying the target displacement; and deriving the desired overlap to obtain the modulation and the required loss. Since the displacement of any one of the membrane (311), baffle (313) or shutter (315) is non-uniform and the amount of displacement depends on the radius. The maximum displacement is obtained at the center of the membrane and zero displacement is obtained at the anchor points of the membrane. Since the displacement is not constant, in one example, the overlap of the orifices across the structure varies according to the distance from the center of the membrane and is related to the membrane displacement at that point.

[0059] In one example, the etching process is an isotropic etching process. Examples of the etching and material combinations include, but are not limited to: a dielectric including SiO2 and an etching process including hydrofluoric acid (HF) or vapor HF (VHF); a dielectric including a polymer layer and an etching treatment including any one of the following, but not limited to the following: oxygen plasma; piranha solution (IPA + H2O2); polymer liquid etchant. In another example, the dielectric includes a photoresist material or a photo-definable material, and the etching material is a developer. In one example, due to the material being exposed to ultraviolet (UV) light, the material changes its chemical property from solubility in the developer to insolubility in the developer. In an alternative example, due to the material being exposed to ultraviolet light, the material changes its chemical property from insolubility in the developer to solubility in the developer.

[0060] In an alternative example, the above process is modified and the dielectric layer is patterned to include two materials. One material serves as a scaffold for the film, while the second material is a sacrificial material that is designed to be removed in an etching process after the layer stack is fabricated. In another example, the etching process includes any one of the following, but is not limited to the following: wet etching, vapor etching such as VHF, or plasma etching including oxide plasma or CF4 and oxide plasma. In one example, the modified process includes a developing step after the dielectric layer is deposited. In an alternative example, the modified process includes: depositing a first dielectric material; applying a photoresist to the first dielectric material; patterning the photoresist by exposing and developing a pattern through a mask; using the photoresist pattern as a mask to etch the first dielectric layer to create at least one cavity in the first dielectric material; applying a second dielectric material to fill the at least one cavity; optionally applying a planarization step to remove any second dielectric that extends beyond the at least one cavity and partially or completely covers the first dielectric. In another example, the first dielectric is any one of the following, but is not limited to the following: silicon oxide; SiOx; SiN; aSi; polymers. Examples of polymers include, but are not limited to, polyamide; SU8; epoxy resin; silicone; photoresist. In a further example, the polymer includes Ti or Si and is resistant to oxide plasma etching after being treated with plasma and / or UV. In another example, the etching of the first dielectric is accomplished using any one of the following, but is not limited to the following: RIE plasma process; DRIE plasma process; wet etching, using any one of the following materials but not limited to the following: CF4; CF6; O2; Ar; combination of gases; HF; Piranha. In another example, the second dielectric is any one of the following, but is not limited to the following: silicon oxide; SiOx; SiN; aSi; polymers. Examples of polymers include, but are not limited to: polyamide; SU8; epoxy resin; silicone; photoresist; PMDS; PVDF. In a non-limiting example, the first dielectric is SiO2; the etching is RIE; and the second dielectric is any one of the following, but is not limited to the following: polyamide; SU8; epoxy resin; silicone; photoresist; PMDS; PVDF, and the sacrificial layer release includes etching using at least oxygen plasma or oxygen plasma enhanced with CF4 or CF6. The structure before releasing the sacrificial layer includes at least: a first layer composed of two dielectric materials; a first metal layer; a second layer composed of two dielectric materials; a second metal layer; a third layer composed of two dielectric materials; and a third metal layer; the structure includes vias that pass through the metal and the dielectric layer composed of the second dielectric etched in the sacrificial layer release process.

[0061] In Figures 4A - 4CDescribes an example of a modified process having a first dielectric and a second dielectric. Figure 4A Is an example of a side view of a micro speaker unit during manufacturing after patterning a membrane layer (301). The micro speaker unit consists of a silicon wafer (350), a first dielectric layer (311), and a patterned membrane layer (301). The first dielectric layer, which is at least partially composed of a photoresist material, is deposited on the silicon wafer. In one example, the first dielectric layer is exposed to ultraviolet light, where the ultraviolet light irradiates the entire wafer area. The ultraviolet light changes the chemical properties of the photoresist, making it removable with a developer. In an alternative example, the photoresist is covered with a membrane cavity mask (441). In one example, the membrane cavity mask defines a first region (451) in the photoresist that will be removed during a final release etch. In another example, the region defined by the membrane cavity mask (441) partially overlaps with the membrane structure defined in the first mask (331). In a second example, a second membrane cavity mask (442) defines a region in the photoresist that will not be removed during the final release etch. In another example, the region defined by the second membrane cavity mask, which has a polarity opposite to that of the first membrane cavity mask (441), partially overlaps with substantially all regions not under the membrane structure defined in the first mask (331), and then only the uncovered regions will be removed. In some examples, the surface flatness of the first dielectric layer is enhanced by any one or combination of the following methods; chemical mechanical polishing (CMP); heat reflux; chemical etching; chemical reflux. The membrane layer is deposited on the first dielectric layer (311). The membrane layer is coated with a second photoresist material. The second photoresist is exposed and developed using the first mask (331) such that the photoresist has the same pattern as the first mask (331). The membrane layer is etched through the exposed photoresist and the first mask pattern is transferred to the membrane layer (Figure 1, 105), thereby producing a patterned membrane layer (301). Developing the membrane layer photoresist does not affect the first dielectric layer because the membrane layer provides a chemical barrier that protects the first dielectric layer from the developer. The membrane layer is etched using a process that does not etch the dielectric layer. In another example, the thickness of the first dielectric layer (311) is any one of the following, but not limited to the following: 1 micron; 2 microns; 3 microns; 4 microns; 1 - 5 microns.

[0062] Figure 4BAn example of a side view of a MEMS speaker unit during manufacturing after patterning the baffle layer (303). A second dielectric layer, at least partially composed of a photoresist material, is deposited on the membrane layer. In one example, the second dielectric layer is exposed to ultraviolet light, where the ultraviolet light irradiates the entire wafer area. The ultraviolet light changes the chemical properties of the photoresist such that it can be removed with a developer. In an alternative example, the photoresist is covered with a baffle cavity mask (443). In one example, the baffle cavity mask (443) defines a second region (453) in the photoresist that will be removed during a final release etch. In another example, the region defined by the baffle cavity mask (443) partially overlaps with the baffle structure defined in the second mask (333). In the second example, a second baffle cavity mask of opposite polarity to the first baffle cavity mask (441) defines a region in the photoresist that will not be removed during the final release etch. In another example, the region defined by the second baffle cavity mask (444) partially overlaps with substantially all of the regions that are not under the baffle structure defined in the second mask (333), and then only the uncovered regions will be removed. In some examples, the surface flatness of the second dielectric layer is enhanced by any one or a combination of the following methods: chemical mechanical polishing (CMP); heat reflux; chemical etching; chemical reflux. The baffle layer is deposited on the second dielectric layer (313). The baffle layer is coated with a photoresist material. A second mask (333) is used to expose the photoresist. Developing the baffle layer photoresist does not affect the first or second dielectric layer because the baffle layer provides a chemical barrier that protects the second or first dielectric layer from the developer. The baffle layer is etched through the exposed photoresist, and the second mask pattern is transferred to the baffle layer (Figure 1, 105), thereby producing a patterned baffle layer (303). In another example, the thickness of the second dielectric layer (313) is any one of the following, but not limited to the following: 4 microns; 5 microns; 1 - 5 microns, 5 - 10 microns; 10 - 20 microns; 20 - 40 microns; less than 50 microns.

[0063] Figure 4CAn example of a side view of a micro speaker unit during manufacturing after patterning the shutter layer (305). A third dielectric layer, at least partially composed of a photoresist material, is deposited on the baffle layer. In one example, the third dielectric layer is exposed to ultraviolet light, where the ultraviolet light irradiates the entire wafer area. The ultraviolet light changes the chemical properties of the photoresist, making it removable with a developer. In an alternative example, the photoresist is covered with a shutter cavity mask (445). In one example, the shutter cavity mask (445) defines a third region (455) in the photoresist that will be removed in a final release etch. In another example, the region defined by the shutter cavity mask (445) partially overlaps with the shutter structure defined in the third mask (335). In a second example, a second shutter cavity mask (446) defines a region in the photoresist that will not be removed in the final release etch. In another example, the region defined by the second shutter cavity mask with an opposite polarity to the first shutter cavity mask (445) partially overlaps with substantially all regions not under the shutter structure defined in the third mask (335), and then only the uncovered regions will be removed. In some examples, the surface flatness of the second dielectric layer is enhanced by any one or a combination of the following methods: chemical mechanical polishing (CMP); thermal reflow; chemical etching; chemical reflow. The shutter layer is deposited on the third dielectric layer (315). The shutter layer is coated with a photoresist material. The third mask (335) is used to expose the photoresist. Developing the shutter layer photoresist does not affect any dielectric layer because the shutter layer provides a chemical barrier to protect the third, second, or first dielectric layer from the developer. The shutter layer is etched through the exposed photoresist and the third mask pattern is transferred to the shutter layer (Figure 1, 103), resulting in a patterned shutter layer (305). In another example, the thickness of the third dielectric layer (315) is any one of the following, but not limited to: 2 microns; 3 microns; 4 microns; 5 microns; 1 - 5 microns, 5 - 10 microns.

[0064] Figure 4C An example of a side view of a micro speaker unit during manufacturing after releasing the membrane (301), baffle (303), and shutter (305) layers. The release of the layers is facilitated by an etching process that partially removes the first (311), second (313), and third (315) dielectric layers (especially under the membrane structure) and effectively releases at least a portion of the membrane (301), baffle (303), or shutter (305) structure.

[0065] Examples of deposition methods for the first, second, and third dielectric layers, for the membrane layer, baffle layer, and shutter layer include but are not limited to: spin coating; chemical vapor deposition (CVD); physical vapor deposition (PVD); sputtering; LPCVD; PECVD.

[0066] Examples of materials for the first, second, and third dielectric layers include, but are not limited to: polyimide; epoxy resin; BCB; SU8; photoresist; silicone; SiO2; SiSOx; SiN; SiRN; SiC; aSi; or other non-conductive polymers; ceramics or glass; combinations of any of the foregoing. In one example, the first, second, and third dielectric layers are composed of the same material. In alternative examples, the first, second, and third dielectric layers are composed of the same or different materials.

[0067] Examples of materials for the membrane (301), baffle (303), and shutter layer (305) include, but are not limited to: polysilicon; silicon; aSi; SiN; SiRN; aluminum; nickel; AlN; PZT; copper; silver; gold; polymers; graphene; conductive materials; layers of conductive and non-conductive materials; piezoelectric materials; or combinations of any of the foregoing materials. In one example, the membrane (301), baffle (303), and shutter layer (305) are composed of the same material. In alternative examples, the membrane (301), baffle (303), and shutter layer (305) are composed of the same or different materials.

[0068] Examples of ultraviolet light include, but are not limited to: light from a laser; light from an LED or lamp that emits at any one of the following wavelengths but is not limited to the following wavelengths: 360 nm; 300 - 310 nm; 300 - 360 nm; 250 nm; 150 - 200 nm; 200 - 300 nm.

[0069] In Figures 4A - 4C Alternative examples of processes described with a first dielectric and a second dielectric are described. The first dielectric material is any one of the following, but is not limited to the following: SiO2; SiOx; aSi; SiN; TiO2; alumina; AlN or combinations thereof, and the second dielectric material is any one of the following, but is not limited to the following: polymers; polyamides; silicone; SU8; PMDS; PVDF; epoxy resins. Figure 4AAn example of a side view of a micro speaker unit during manufacturing after patterning a first film layer (301). The micro speaker unit consists of a silicon wafer (350), a first dielectric layer (311), and a patterned first film layer (301). The first dielectric layer consists of at least two dielectric materials. The first dielectric material is deposited on the wafer (350). A photoresist layer is deposited on the first dielectric layer (311). The photoresist is patterned by exposure and development through a first mask (441). The first dielectric material (311) is etched using the photoresist pattern as a mask to create at least one cavity in the first dielectric material (311). A second dielectric is deposited and fills the cavity and optionally covers at least a portion of the first dielectric material (311). If the second dielectric material covers the top of the first dielectric material (311), the second dielectric material is planarized by any one of but not limited to a combination of the following: plasma etching; CMP; reflow. The resulting dielectric layer includes a first dielectric material (311) and a second dielectric material (451) having substantially the same height. A film layer is deposited on the first dielectric layer (311, 451). The film layer is coated with a second photoresist material. The second photoresist is exposed and developed using a second mask (331) such that the photoresist has the same pattern as the second mask (331). The film layer is etched through the photoresist pattern and the second mask pattern (331) is transferred to the film layer (Figure 1, 105), thereby creating a patterned film layer (301). Developing the film layer photoresist does not affect the first dielectric layer because the film layer provides a chemical barrier that protects the first dielectric layer from the developer. In one example, the film layer is etched using a process that does not etch the dielectric layer. In an alternative example, the dielectric is etched but then covered during the deposition of the next layer. In another example, a thin layer of dielectric is deposited before depositing the film layer. Examples of thicknesses include but are not limited to 100 nm, 200 nm, or less than 300 nm. The dielectric thin layer provides additional protection to the sacrificial layer during removal of the mask material. In another example, the thickness of the first dielectric layer (311, 451) is any one of but not limited to the following: 1 micron; 2 microns; 3 microns; 4 microns; 1 - 5 microns. In another example, the film layer includes a bottom dielectric layer and a top metal layer. The bottom dielectric layer serves two functions. From a functional perspective, the bottom dielectric layer prevents short circuits from occurring when the film layer contacts another film layer during device operation. From a process perspective, the bottom dielectric layer provides an etch-resistant layer that enables the metal layer to be etched using wet etching without damaging the sacrificial layer. The dielectric layer is then etched using an RIE process. Examples of materials for the bottom dielectric layer include SiO2; SiOX; SiN. The thickness of the bottom dielectric layer is less than 0.5 microns.

[0070] Figure 4BAn example of a side view of a micro-speaker unit during manufacturing after patterning the baffle layer (303). The micro-speaker unit consists of: a silicon wafer (350), a first dielectric layer (311, 441) and a first patterned film layer (301), a second dielectric layer (313, 453) and a second patterned film layer (303). The second dielectric layer consists of at least two dielectric materials. A first dielectric material is deposited on the first patterned film layer (301). A photoresist layer is deposited on the second dielectric layer. The photoresist is patterned by exposing and developing the photoresist through a third mask (443). The first dielectric material is etched using the photoresist pattern as a mask to create at least one cavity in the first dielectric material (313). A second dielectric is deposited and fills the cavity and optionally covers at least part of the first dielectric material in the second dielectric layer (313). If the second dielectric material covers the top of the first dielectric material of the second dielectric layer (313), the second dielectric material is planarized by any one of the following but not limited to a combination of the following: plasma etching; CMP; reflow. The resulting second dielectric layer includes a first dielectric material (313) and a second dielectric material (453) having substantially the same height. A second film layer is deposited on the second dielectric layer (313, 453). The second film layer is coated with a photoresist material. The photoresist is exposed and developed using a fourth mask (333) such that the photoresist has the same pattern as the fourth mask (333). The second film layer is etched through the photoresist pattern, and the fourth mask pattern (333) is transferred to the second film layer (Figure 1, 107), resulting in a patterned film layer (303). Developing the photoresist of the second film layer does not affect the second or first dielectric layer because an intervening layer provides a chemical barrier that protects the dielectric layer from the developer. The film layer is etched using a process that does not etch the dielectric layer. In another example, the thickness of the second dielectric layer (313, 453) is any one of the following but not limited to the following: 1 micron: 2 microns; 3 microns; 4 microns; 1 - 5 microns. In another example, the film layer includes a bottom dielectric layer and a top metal layer. The bottom dielectric layer serves two functions. From a functional perspective, the bottom dielectric layer prevents short circuits from occurring when the film layer contacts another film layer during device operation. From a process perspective, the bottom dielectric layer provides an etch-resistant layer that enables the metal layer to be etched using wet etching without damaging the sacrificial layer. The dielectric layer is then etched using an RIE process. Examples of materials for the bottom dielectric layer include SiO2; SiOX; SiN. The thickness of the bottom dielectric layer is less than 0.5 microns.

[0071] Figure 4CAn example of a side view of a picoyear speaker unit during manufacturing after patterning the shutter layer (305). The picoyear speaker unit consists of: a silicon wafer (350), a first dielectric layer (311, 441) and a first patterned film layer (301), a second dielectric layer (313, 453) and a second patterned film layer (303), a third dielectric layer (315, 455) and a third patterned film layer (305). The third dielectric layer consists of at least two dielectric materials. A first dielectric material is deposited on the second patterned film layer (303). A photoresist layer is deposited on the third dielectric layer. The photoresist is patterned by exposing and developing the photoresist through a fifth mask (445). The first dielectric material is etched using the photoresist pattern as a mask to create at least one cavity in the first dielectric material (315). A second dielectric is deposited and fills the cavity and optionally covers at least part of the first dielectric material in the second dielectric layer (315). If the second dielectric material covers the top of the first dielectric material of the second dielectric layer (315), the second dielectric material is planarized by any one of the following but not limited to a combination of the following: plasma etching; CMP; reflow. The resulting second dielectric layer includes a first dielectric material (315) and a second dielectric material (455) having substantially the same height. A third film layer is deposited on the second dielectric layer (315, 455). The third film layer is coated with a photoresist material. The photoresist is exposed and developed using a sixth mask (335) such that the photoresist has the same pattern as the fourth mask (335). The third film layer is etched through the photoresist pattern, and the sixth mask pattern (335) is transferred to the third film layer (Figure 1, 109), thereby creating a patterned film layer (305). Developing the photoresist of the second film layer does not affect the third, second, or first dielectric layers because the intermediate layer provides a chemical barrier that protects the dielectric layers from the developer. The third film layer is etched using a process that does not etch the dielectric layers. In another example, the thickness of the third dielectric layer (315, 455) is any one of the following but not limited to the following: 1 micron; 2 microns; 3 microns; 4 microns; 1 - 5 microns. In another example, the film layer includes a bottom dielectric layer and a top metal layer. The bottom dielectric layer provides two functions. From a functional perspective, the bottom dielectric layer prevents short circuits from occurring when the film layer contacts another film layer during device operation. From a process perspective, the bottom dielectric layer provides an etch-resistant layer that enables the metal layer to be etched using wet etching without damaging the sacrificial layer. The dielectric layer is then etched using an RIE process. Examples of materials for the bottom dielectric layer include SiO2; SiOX; SiN. The thickness of the bottom dielectric layer is less than 0.5 microns.

[0072] In another example, a fourth dielectric layer is deposited on the top side of the third patterned film layer (305). The fourth dielectric layer provides a protective layer over the third patterned film layer. In one example, the fourth dielectric layer is composed of a second dielectric and is thus removed during sacrificial layer etching and film release. Figure 4A , Figure 4B and Figure 4C the membrane patterns shown in are illustrative and not limited to specific examples.

[0073] As described in Figures 3A - 3D and Figures 4A - 4C the method of manufacturing MEMS devices is not limited to MEMS speaker devices. Many MEMS devices require structural release, and common methods include etching by VHF, HF, or XeFe. The methods described in this disclosure provide a low-cost, simple alternative to existing methods for manufacturing various MEMS devices that require structural release. Examples of MEMS devices that require structural release include, but are not limited to: RF switches; micro mirrors, accelerometers, gyroscopes, pressure sensors, barometers, inkjet dispensers, ultrasonic sensors, timing devices, temperature sensors, thermal imaging sensors, and bolometers.

[0074] Figure 5A is an alternative example of a mask for a single unit that defines the membrane layer mask (531). In contrast to the previous example of the membrane layer mask ( Figure 3A , 331), the membrane layer mask does not include an aperture. In another example, the membrane layer mask includes an etch through hole for facilitating the etching of the first dielectric layer ( Figure 4C , 311) and the release of the membrane layer ( Figure 4C , 301). Examples of the etch through hole include apertures less than 2 microns and are not shown in the figure. In another example, the center-to-center spacing of the apertures depends on the thickness of the first dielectric layer ( Figure 4C , 311) and ranges from 10 to 25 microns. Figure 5B is an alternative example of a mask for a single unit that defines the baffle layer mask (535), which includes apertures (541, 543, 545) for acoustic power transmission. Figure 5C is an alternative example of a mask for a single unit that defines the shutter layer mask (533), which includes an aperture (551) for acoustic power transmission. The aperture (551) in the shutter layer does not overlap with the apertures in the baffle layer. The distance between the apertures in the horizontal plane provides acoustic attenuation of the outgoing ultrasonic signal. The attenuation depends on the distance and the gap between the shutter and the baffle. In another example, the baffle layer mask (533) and the shutter membrane mask (535) include for facilitating the first dielectric layer (Figure 4C , 311) Etching and film layer( Figure 4C , 301) Released etched vias. Examples of etched vias include apertures less than 2 microns, and are not shown in the figure. In another example, the center-to-center spacing of the apertures depends on the thickness of the first dielectric layer( Figure 4C , 311) and ranges from 10 to 25 microns.

[0075] Figure 5D is an example of a 3×4 unit array (531, 533, 535) of devices fabricated from a previous mask layer. Figure 5E is an example of a 15×20 array of MEMS speaker devices (561) fabricated from units of a previous mask layer. The speaker device consists of multiple units. The MEMS speaker device includes at least, but is not limited to: multiple units (563) that generate audio signals and / or ultrasonic signals; one or more pads (591, 593, 595, 597) that are in electrical contact with any layer in the MEMS speaker device layer; a membrane( Figure 1A , 105); a baffle( Figure 1A , 103); a shutter( Figure 1A , 101); a handle( Figure 1A , 107). The MEMS speaker device (561) is assembled on a substrate (565). Examples of the substrate include at least, but are not limited to: PCB; ceramics; silicon-based platform (Siliconbench); flexible laminate; other metal polymer laminates. Examples of assembly include at least, but are not limited to: bonding; soldering; reflow. Additional devices assembled on the substrate include at least, but are not limited to: a driving device (109); one or more containers (569); passive devices, including any one of the following, but not limited to the following: capacitors; inductors; resistors; diodes. The substrate also includes electrical traces (571, 573, 575, 577, 579) that provide a conduction path from the driving device (109) to the passive devices and / or the MEMS speaker device (561). In one example, electrical connections to the membrane layer are facilitated from one side of the array, electrical connections to the baffle layer are facilitated from a second side of the array, and electrical connections to the shutter region are facilitated from a third side of the array.

[0076] Acoustic transducers benefit from pressure relief holes, examples of which are common in MEMS microphones where the microphone membrane is not impeded by a top or bottom cavity. Figure 6AAn example of a modified micro-speaker that includes a dorsal hole (501). The dorsal hole (501) provides acoustic pressure relief and in one example is etched in a carrier wafer (350) by dorsal etching. Examples of the carrier wafer and its corresponding etching process include but are not limited to: a silicon carrier wafer and an etching process that includes any one of the following but is not limited to the following: reactive ion etching (RIE); deep reactive ion etching (DRIE); Bosch process DRIE; wet etching; KOH; TMMA; laser drilling; ion milling; a ceramic wafer and an etching process that includes laser drilling; ion milling; a metal wafer or panel, where the metal includes but is not limited to aluminum; copper; nickel; stainless steel; and combinations thereof, and the etching process includes: laser drilling; wet etching; ion milling. In one example, the hole is substantially the size of the membrane structure above it. In an alternative example, the hole is up to 60% smaller than the structure above it. In another alternative example, the hole is larger than the structure above it and can include two or more units.

[0077] Figure 6B An alternative example of a micro-speaker unit with a dorsal hole and an additional reference layer. The reference layer is fabricated from a conductive material in a manner similar to a membrane, baffle layer, or shutter layer. Examples of reference layer materials include but are not limited to: aluminum; nickel; gold; silicon; graphene or a conductive polymer or combinations thereof. In some examples, the membrane of the micro-speaker is electrostatically actuated. In these examples, a voltage is applied to one membrane while a second voltage is applied to an adjacent membrane layer. Examples of actuation include but are not limited to: applying an actuation voltage to the shutter, applying a ground or zero voltage to the baffle layer, and applying a second actuation voltage to the membrane layer. The voltage difference between the shutter / baffle and the baffle / membrane creates an electrostatic force that pulls the membrane or shutter towards the baffle layer. In examples where the distance between the membrane and the baffle layer is large, the electrostatic force generated is weak and the displacement generated does not produce sufficient acoustic power. Using Figure 6B An alternative actuation method for the micro-speaker unit shown is to apply an actuation voltage to the shutter, a ground or zero voltage to the baffle layer, a second actuation voltage to the membrane layer, and a ground voltage or zero voltage to the reference layer. In this example, the distance between the membrane and the reference layer is selected to produce the maximum displacement for the minimum actuation voltage. Examples of the distance include but are not limited to: 2 microns; 3 microns; 4 - 6 microns. Without any change in the operation of the micro-speaker, the actuation voltage and ground can be interchanged.

[0078] In another example, the dorsal aperture is part of the acoustic cavity. The acoustic cavity is coupled to one or more dorsal apertures. In one example, the acoustic cavity includes a Helmholtz resonator having a resonant frequency lower than any one of, but not limited to, the following: 20 Hz; 100 Hz; 500 Hz; 1 kHz; 2 - 5 kHz. In another example, the dorsal aperture and / or cavity includes a channel having at least one dimension less than any one of, but not limited to, the following: 10 microns; 50 microns; 100 microns; 200 microns; 500 microns. For a given acoustic cavity volume, the narrow channel dimension results in a lower speed of sound and a reduction in the resonant frequency. In another example, at least one boundary of the acoustic cavity is a flexible membrane. In another example, the resonant frequency of the flexible membrane is lower than any one of, but not limited to, the following: 20 Hz; 100 Hz; 500 Hz; 1 kHz; 2 - 5 kHz; lower than the resonant frequency of the Helmholtz resonator of the acoustic cavity. The flexible membrane interacts acoustically with the acoustic signal in the cavity and, due to the lower resonant frequency, it acts in antiphase and serves to suppress the acoustic signal in the cavity. The desired acoustic signal is generated by the cavity or the flexible membrane.

[0079] In another example, the actuation voltage is a time-varying signal. In one example, the time-varying signal is a pulse-width modulation (PWM) signal, where the repetition rate of the pulses is aligned with the resonant frequency of the shutter, and the variation in pulse width provides modulation of the shutter or the membrane. Figure 7 is an example of a PWM signal, where the PWM signal has two voltage values and the pulse width varies from pulse (701) to pulse (703). In one example, the shutter actuation voltage is a PWM signal with a fixed duty cycle, the fixed duty cycle being optimized to obtain the maximum displacement of the shutter, and the membrane actuation voltage is a PWM signal with a varying duty cycle. The instantaneous pulse width or duty cycle is obtained by converting the audio signal a(t) into a pulse width.

[0080] Figure 8is a conversion method from a(t) to pulse width. In one example, the fixed duty cycle for shutter actuation is any one of the following, but not limited to the following: 30%; 40%; 50%; any value between 30 - 50%. Due to the limitation of the maximum pulse width (which is at most 50% of the operating frequency time interval), the potential limitation of the conversion method from a(t) to pulse width is the dynamic range of the input signal and the required resolution. Due to limitations such as switching time or pulse rise or fall time, the resolution provided by the potential pulse width values is lower than that required by the signal resolution (examples are the dashed lines 801 - 813). An example of a method for increasing the achievable resolution is to employ sigma delta modulation. Delta-sigma (ΔΣ; or sigma-delta, ΣΔ) modulation is a method for encoding an analog signal into a digital signal, as found in an analog-to-digital converter (ADC). It is also used to convert a high bit-count, low-frequency digital signal into a lower bit-count, higher-frequency digital signal, as part of the process for converting a digital signal into an analog one, as part of a digital-to-analog converter (DAC). In a traditional ADC, the analog signal is sampled at the sampling frequency and subsequently quantized into a digital signal in a multi-level quantizer. This process introduces quantization error noise. The first step in delta-sigma modulation is delta modulation. In delta modulation, the change in the signal (its delta) is encoded, rather than the absolute value being encoded. The result is a stream of pulses, rather than a stream of digits as in the case of pulse code modulation (PCM). In delta-sigma modulation, the modulation accuracy is improved by passing the digital output through a 1-bit DAC and adding the resulting analog signal to the input signal (the signal before delta modulation) (sigma), thereby reducing the error introduced by delta modulation. This method follows the method for sigma delta DAC. A high-resolution audio digital input signal is mapped to a signal with lower resolution but higher sampling frequency. For example, an audio signal with a bandwidth of 10KHz is mapped to a membrane PWM drive signal of 400KHz. The drive signal drives the membrane that acts as a filter and provides a smoothing function for the resulting acoustic signal. In another example, the digital audio signal is processed according to the sigma-delta algorithm to provide a drive signal suitable for the dynamic range of the micro speaker before transmitting the digital audio signal to the micro speaker.

[0081] Figure 9AThis is an example of an operation method for a micro speaker. This method is timed by a central clock (911). In one example, the central clock (911) operates at any frequency between any of the following ranges, but is not limited to the following ranges; 1 - 10 MHz; 10 - 100 MHz; 100 - 1000 MHz. The operating frequency is selected to be consistent with an integer divisor of the central clock frequency; Fw = Fc / N, where Fw is the operating frequency, Fc is the clock frequency, and N is an integer. In one example, Fw is 300 KHz, Fc = 7,680 KHz, and N = 2 10 . The audio digital signal is provided in a serial format such as I2S. The audio is sampled at an audio rate, examples of which include but are not limited to (6.14 / J / 2) KHz, where J is a 64 - bit integer. The audio is sampled and processed at a rate that supports the dynamic range achievable by the micro speaker driver circuit. Examples of micro speaker rates include but are not limited to: 48 KHz, 96 KHz. When powered on, the micro speaker executes an initialization program (901). Examples of the initialization process (901) include but are not limited to: identifying the operating frequency of the device; setting appropriate operating parameters, including the device ID; communicating with the host device. The digital audio signal is received at the micro speaker driver device (903) via an appropriate receiver and data extraction algorithm. The clock is isolated from the data, and the sampled audio is further extracted from the received data (905). A signal clock is provided to the central clock as a means for synchronizing the device. In one example, the digital audio signal is pre - processed in a pre - processing block (907). Examples of pre - processing include but are not limited to: filtering; pre - emphasis; dithering; encoding; up - sampling or down - sampling; quantization or a combination of these. In another example, all pre - processing is completed before the transmission of the digital audio signal, and there is no pre - processing block (907). Then the sampled audio data is used to drive the shutter and the diaphragm (909). The above operations are repeated at time intervals that are the reciprocal of the operating frequency. Figure 9B This is an example of a method for implementing the driving of the shutter and diaphragm block (909). Figure 9BThe method includes: initializing t, for example by setting t = 0, where t is the running clock; providing a signal to operate a switch (921) that connects the shutter layer to a high-voltage source; providing a signal to operate a switch (923) that connects the membrane layer to a high-voltage source; checking whether the time elapsed since initialization is greater than the "on" time (Ts) of the shutter-related pulse (925); if so, connecting the shutter layer to a low-voltage source (931); if not, then checking whether the time elapsed since initialization is greater than the "on" time (Tm) of the membrane (927); if so, connecting the membrane layer to a low-voltage source (933); if not, then if the elapsed time is greater than the operating frequency period (Twf = (operating frequency)-1), repeating block 925, and if not, repeating block 921. In a further example, the "on" time of the shutter is determined by a duty cycle optimized to achieve the maximum displacement of the shutter layer, where examples of the duty cycle include, but are not limited to: 50%; 40 - 50%; 30 - 40%. The "on" time (Ts) of the shutter is an example of a parameter loaded by the initialization process (Figure 9A 901). The "on" time (Tm) of the membrane is determined according to the method outlined above and is shown in Figure 8 The membrane is driven by PWM actuation, where the pulse width corresponds to a digital audio sample. In one example, the low-voltage source is a ground terminal. In another example, the low-voltage source is a charge recycling unit.

[0082] Figure 10 is an example of a driving device ( Figure 1B , 109) that is connected to a micro speaker and supplies power to the membrane layer ( Figure 1B , 105) and the shutter layer ( Figure 1B, 101) Provide an actuation signal. The driving device is a semiconductor integrated circuit, which includes but is not limited to the following units: a communication unit (1001); a charge pump configured to receive a low-voltage signal and generate a high-voltage signal (1003); a switching unit configured to modulate the high-voltage signal (1005); a control unit (1007). The driving unit receives a digital audio data stream via line (119) and receives an operating voltage via line (121). The driving unit (109) is connected to the membrane layer via line (115), connected to the shutter layer via line (113), and connected to the baffle layer via line (103). In another example, the switching unit (1005) alternates between two states: a high-voltage state, in which the switching unit (1005) connects the high-voltage signal to either or both of the membrane and the shutter; a low-voltage state, in which the switching unit (1005) connects a low voltage or a ground voltage to either or both of the membrane and the shutter. In another example, the driving device further includes a charge recycling unit (1009). The charge recycling unit consists of capacitive elements and is alternatively connected to the switching unit (1005) and the charge pump (1003). When the membrane or shutter voltage is set to a high voltage, the switching unit (1005) connects the charge pump (1003) to the charge recycling unit (1009), and a portion of the charge accumulated by the charge pump (1003) is provided by the charge recycling unit (1009). When the membrane or shutter voltage is set to low, the charge recycling (1009) is connected to the membrane or shutter and charge is transferred from the membrane or shutter to the charge recycling unit (1009). The membrane and the shutter operate independently and both require the switching unit (1005) and the charge recycling unit (1009). In one example, the charge pump is shared by both the membrane and the shutter layers. In an alternative example, each layer has its own charge pump.

[0083] In one example, a driving device (109) connected to a MEMS speaker includes at least two of: a charge pump (1003); a control unit (1007); a communication unit (1001); a switching unit (1005) having two or more switches; one of the switches connecting the charge pump (1005) to the membrane ( Figure 1A , 105), and a second switch connecting the charge pump (1005) to the shutter ( Figure 1A , 101); and wherein the control unit (1007) operates the switching unit (1005) to generate a modulated ultrasonic signal from the membrane ( Figure 1A , 105) and an audio signal from the action of the shutter ( Figure 1A , 101).

[0084] Figure 11A is a pico speaker unit ( Figure 1A, an alternative example of a schematic representation of (121). The micro speaker unit includes, but is not limited to, an ultrasonic source (1103) and an acoustic variable coupler (1105). In another example, the acoustic variable coupler (1105) makes acoustic contact via an acoustic output aperture (1121) having a free propagation region, while in another alternative example, the variable output coupler (1105) makes acoustic contact with an acoustic impedance matching unit (1107) via the acoustic output aperture (1121). In another example, an acoustic impedance matching unit (1107) is provided for each speaker unit. In another alternative example, an acoustic impedance matching unit (1107) is provided for multiple units or for the entire speaker. Examples of the acoustic impedance matching unit (1107) include: ear canals; acoustic horns; impedance matching layers; acoustic channels. The acoustic impedance matching unit (1107) is acoustically coupled to the target medium via an acoustic medium aperture (1129), and the target medium includes, but is not limited to: air; a closed volume, and efficiently transmits the audio signal into the target medium. In one example, the ultrasonic source includes: at least one vibrating membrane (105) that is enclosed in an acoustic chamber (1111), and the acoustic chamber has an acoustic aperture (1115) connected to the acoustic variable coupler (1105). The vibrating membrane (105) vibrates in the acoustic chamber (1111) and generates a modulated ultrasonic signal as described in Equation (1). The acoustic chamber (1103), the acoustic aperture (1115), and the acoustic variable coupler (1105) form a Helmholtz resonator. The resonant frequency is determined by the mechanical dimensions of the acoustic chamber (1103), the acoustic aperture (1115), and the acoustic variable coupler (1105). In one example, the resonant frequency is selected to be consistent with the frequency of the shutter ( Figure 1A , 101). In an alternative example, the resonant frequency is selected to be lower or higher than the frequency of the shutter ( Figure 1A , 101). In this representation, the micro speaker generates an audio signal by modulating the output coupling of the ultrasonic source (1103) that generates the ultrasonic signal. In another example, the ultrasonic signal is a modulated ultrasonic signal. In another example, the ultrasonic source (1103) includes at least, but is not limited to, a vibrating membrane (105), an acoustic chamber (1103), and an acoustic aperture (1115). In another example, the acoustic chamber (1103) is acoustically connected to the acoustic variable coupler (1105) via the acoustic aperture (1115). In one example, the acoustic variable coupler (1105) is composed of a baffle ( Figure 1A , 103) and a shutter ( Figure 1A , 101). The acoustic impedance that determines the ratio of the acoustic signal power at the ultrasonic source (1103) side (1115) of the variable coupler (1105) to the opposite side (1121) of the variable coupler is modulated, thereby producing the effects described in Equations (3) and (4). In one example, the baffle ( Figure 1A , 103) and the shutter (Figure 1A , the relative position of (101) determines the acoustic impedance of the variable coupler (1105). Alternative mechanisms for variable coupling include, but are not limited to: changes in local air pressure; changes in local temperature; electroacoustic materials whose speed of sound varies according to the applied voltage. In another example, the acoustic chamber (1103) includes an acoustic (1120) or an acoustic-mechanical resonator (1120) that is acoustically coupled to the acoustic chamber (1103). A Helmholtz resonator is an example of an acoustic resonator and is implemented by introducing a pipe or duct connected to the acoustic chamber, where the length and width of the pipe are designed to introduce an acoustic resonance frequency of less than 1,000 Hz and preferably less than 500 Hz. In another alternative example, the acoustic-mechanical resonator (1120) is a flexible membrane having a resonance frequency of less than 1,000 Hz and preferably less than 500 Hz. The acoustic-mechanical resonator (1120) is similar to a bass reflex speaker with a dummy speaker cone and provides a method for reducing the effective acoustic resonance of a speaker system. The acoustic or acoustic-mechanical resonator (1120) is coupled to a closed cavity or a free propagation region, which provides the resonator. In one example, an acoustic or acoustic-mechanical resonator (1120) is provided for each speaker unit. In an alternative example, an acoustic or acoustic-mechanical resonator (1120) is provided for multiple units or for the entire speaker.

[0085] Figure 11B is a pico speaker unit ( Figure 1A , 121), another example of a schematic diagram, where the sound source includes one or more acoustic apertures (1115, 1125, 1127). The acoustic apertures provide any of the following paths for the acoustic signal generated in the ultrasonic source (1103): a path to the air volume on the front side of the pico speaker; a path to the air volume on the back side of the pico speaker; a path to one or more adjacent pico speaker units ( Figure 1A); a common rear or front cavity; in another example, the acoustic chamber (1103) includes an acoustic (1120) or an acoustic-mechanical resonator (1120) that is acoustically coupled to the acoustic chamber (1103). A Helmholtz resonator is an example of an acoustic resonator and is implemented by introducing a duct or conduit connected to the acoustic chamber, where the length and width of the duct are designed to introduce an acoustic resonance frequency of less than 1,000 Hz and preferably less than 500 Hz. In another alternative example, the acoustic-mechanical resonator (1120) is a flexible membrane having a resonance frequency of less than 1,000 Hz and preferably less than 500 Hz. The acoustic-mechanical resonator (1120) is similar to a bass-reflex speaker with a virtual speaker cone and provides a way to reduce the effective acoustic resonance of a speaker system. The acoustic or acoustic-mechanical resonator (1120) is coupled to an enclosed cavity or a free-propagation region, which provides the resonator. In one example, an acoustic or acoustic-mechanical resonator (1120) is provided for each speaker unit. In an alternative example, an acoustic or acoustic-mechanical resonator (1120) is provided for multiple units or for the entire speaker.

[0086] Figure 11C is an example of a picoloudspeaker unit ( Figure 4C ), where the dashed-line overlay shows the positions of the following: a sound source (1131); a time-varying acoustic coupler (1133); and an acoustic medium (1135). In another example, the picoloudspeaker unit ( Figure 4C) includes a dorsal hole (501). In one example, the speaker device consists of: at least one ultrasonic source (1131) that is coupled to an acoustic medium (1135) through at least one time-varying acoustic coupler (1133) and generates an audio signal. In another example, the ultrasonic source (1131) is an acoustic cavity having at least one moving surface (1171) that generates a modulated ultrasonic signal. In another example, the time-varying acoustic coupler (1133) includes a low-impedance acoustic medium (1141) covered by at least a top surface (1175) and a bottom surface (1173), and each of the top surface (1175) and the bottom surface (1173) includes a high-impedance acoustic medium. In another example, the time-varying acoustic coupler (1133) includes an acoustic medium (1141) with a sound speed of Vm, which is covered by at least a top surface (1175) and a bottom surface (1173), and each of the top surface (1175) and the bottom surface (1173) includes an acoustic medium with a speed of Vs, and where Vs > Vm. In another example, the time-varying acoustic coupler (1133) includes an acoustic medium (1141) with a sound speed of Vm, which is covered by at least a top surface (1175) and a bottom surface (1173), and each of the top surface (1175) and the bottom surface (1173) consists of an acoustic medium with a speed of Vs, and where Vs > 2*Vm. In another example, the time-varying acoustic coupler (1141) includes an acoustic input port (1157) in contact with the ultrasonic source (1131) and acoustic output ports (1153, 1155) in contact with the acoustic medium (1135), and where the time-varying change of the physical parameters of the time-varying acoustic coupler (1133) includes but is not limited to: the structural dimensions of the acoustic coupler; the acoustic impedance of the acoustic coupler; the change in the ratio of the acoustic power entering the acoustic input port (1157) to the acoustic power leaving the acoustic output ports (1153, 1155). In another example, the time-varying change of the physical parameters is periodic. In another example, the width and length of the dorsal hole (501) are designed to provide an acoustic resonator (1120) coupled to the ultrasonic source (1131). It should be noted that for small apertures, the air velocity will decrease, so apertures with a width between 10 - 100 microns and a length between 100 and 2,000 microns can be used to achieve a low resonance frequency. In yet another example, the acoustic resonator (1120) includes multiple cavities, where the common cavity of the ducts acoustically couples all the cavities. In another alternative example, the acoustic mechanical resonator is realized by attaching a membrane to the dorsal side of a wafer (350). The membrane is designed to have a mechanical resonance of less than 1,000 Hz or less than 500 Hz. Examples of the membrane are polyester film, parylene, polyamide, aluminum, or other polymer or metal layers with a thickness of less than 5 microns and a size greater than 1 mm. The membrane is coupled to one or more ultrasonic sources (1131). In another example, the ultrasonic source includes one or more ultrasonic membranes.

[0087] In an alternative example, the loudspeaker device consists of: at least one ultrasonic source (1131) that generates a modulated ultrasonic signal and consists of a cavity and at least one source acoustic port (1151); a time-varying acoustic coupler (1131) having an input acoustic port (1157) and output acoustic ports (1153, 1155); wherein the source acoustic port (1151) is connected to the input acoustic port (1157), and the output acoustic ports (1153, 1157) are connected to an acoustic medium (1135); and wherein the signal at the output ports (1153, 1155) includes an audio signal.

[0088] In an alternative example, the loudspeaker device consists of: at least one ultrasonic source (1131) coupled to an acoustic medium (1137) by at least one time-varying acoustic coupler (1135); a drive device ( Figure 1A , 109) that is configured to operate: one or more ultrasonic sources (1131); one or more time-varying acoustic couplers (1135); and to generate an audio signal in the acoustic medium (1137); in another example, the drive device ( Figure 1A , 109) will: provide a first PWM electrical signal to one or more ultrasonic sources (1131) to generate a modulated ultrasonic signal; provide a second PWM electrical signal to one or more time-varying acoustic couplers (1133) to generate an audio signal portion of the modulated ultrasonic signal.

[0089] In an alternative example, the loudspeaker device at least includes: a MEMS device, wherein the MEMS device at least includes an ultrasonic source (1131) and a time-varying acoustic coupler (1133); a drive device ( Figure 1A , 109) that communicates with the MEMS device and is configured to operate the ultrasonic source (1131) and the time-varying acoustic coupler (1133) to generate an audio signal.

[0090] In one example, the membrane and the shutter operate asynchronously or independently. In another example, the shutter operates at the shutter resonance frequency to achieve maximum acoustic modulation. The membrane operates at one or more frequencies. Examples of membrane operation include, but are not limited to: a signal including an audio signal multiplied by a carrier frequency corresponding to the shutter resonance frequency; a signal including an audio signal multiplied by a carrier frequency corresponding to the shutter resonance frequency, wherein carrier modulation is suppressed; a signal including an upper sideband or a lower sideband of an audio signal multiplied by a carrier frequency corresponding to the shutter resonance frequency; or a combination of these signals.

[0091] In another example, the membrane and the shutter operate synchronously at the same frequency. In another example, the frequency corresponds to the shutter resonance frequency. The amplitude of the generated audio signal is controlled by any one of the following, but not limited to the following: the relative phase of the membrane and shutter operations; the amplitude of the shutter operation; the amplitude of the membrane operation; any combination of these.

[0092] Examples of the size of the pico speaker unit include, but are not limited to: layer height; structural horizontal dimension; and distance between units. The size of the pico speaker is designed using multi-physics simulation tools that consider the mechanics, electrostatics, and acoustics of the structure. A major aspect of the design is the choice of operating frequency. The operating frequency is the center frequency of the US signal and in one example corresponds to the resonance frequency of the shutter. In an example where the shutter is actuated by a constant PWM signal, the shutter actuation is optimized to obtain the maximum displacement for the minimum actuation voltage. One example of the optimization is to select the shutter electromechanical resonance to correspond to the operating frequency. In another example, the operating frequency is selected to correspond to the shutter resonance frequency. The electromechanical resonance condition is achieved by designing the shutter shape and layer thickness. In one example, the shutter has a diameter of 100 - 170 microns, a layer thickness of 1 micron, and follows Figure 2 the design. In another example, the diameter of the pico speaker unit is 20 - 100 microns larger than the shutter diameter. The additional diameter length is required to provide mechanical anchors for the holding layer, as well as limitations in the processing and release layer etching, such as Figures 3A - 3D or Figures 4A - 4CAs described in. For the above example, the corresponding operating frequency is 300 KHz. Other size and operating frequency options are possible. Further design limitations come from the interaction between the microstructures and the air viscosity. Simulations have shown that very high air pressures reduce the effective modulation of the shutter and the aperture. Therefore, the design needs to ensure that the pressure at the baffle / shutter is low enough to maintain efficient modulation. In one example, the pressure is reduced by creating a backside aperture as described previously. In another example, the pressure is reduced by increasing the distance between the membrane and the baffle layer. Examples of the target distance include, but are not limited to: greater than 5 microns; greater than 10 microns; greater than 20 microns. The modulator action is obtained by moving the shutter with reference to the baffle layer. The movement changes the height of the overlapping region. A smaller height results in a larger acoustic impedance and a lower ultrasonic signal. A key aspect of the modulator design is the shutter / aperture overlap. Previously published designs were limited to at most 10 microns. By reducing the pressure from the modulator, designs with an overlap value of 10 - 25 microns are possible and provide an efficient modulation value of up to 90%. That is, compared to an open modulator, the signal entering the modulator will be attenuated by up to 90% by the closed modulator. The advantage of a larger overlap is that it reduces the displacement required to achieve the target modulation. Reducing the displacement provides two benefits: reducing the required voltage and power requirements; reducing the pressure generated due to the mechanical movement of the shutter. The pressure accumulated due to the shutter movement hinders modulation and provides no benefit in terms of picoloudspeaker operation. Therefore, the design goal is to obtain the maximum modulation with the minimum shutter movement. To best utilize the shutter and baffle structural areas, the baffle and shutter can include several non-overlapping apertures. The overlap between the shutter and the baffle is related to the shutter displacement. However, the shutter displacement is not fixed over the shutter area but depends on the shutter shape and the actuation method. Therefore, in one design example, for the picoloudspeaker unit, the baffle shutter overlap is not constant. An example of the overlap at the inner radius is 15 microns, and an example of the overlap at the outer radius is 20 microns. In one example, the baffle cover design includes a central aperture and at least two peripheral radial apertures. The shutter mask design includes two or more radial apertures: the starting radius R1 = Bo + O1, where Bo is the baffle central hole radius and O1 is the overlap between the central baffle hole and the shutter aperture; the ending radius of R2 = Bo + O1 + Rs, where Rs is the radial width of the shutter aperture. Two or more pylons supporting the central part pass through the shutter aperture. The width of the pylon is defined by the angle α or a constant width w. The design of the shutter mask includes the selection of these values to meet the electromechanical requirements for the shutter to resonate at the operating frequency while providing the required acoustic path and modulation. The following table provides examples of the values:

[0093] Name Minimum Value Typical Value Maximum Value Unit Bo 5 10 25 Micron <![CDATA[O1]]> 5 20 40 Micron <![CDATA[R s > 5 10 25 Micron

[0094] In one example, a loudspeaker device is summarized, which includes: at least one ultrasonic source coupled to an acoustic medium through at least one time-varying acoustic coupler; a loudspeaker driving device configured to at least operate: one or more ultrasonic sources and one or more time-varying acoustic couplers, and generate an audio signal in the acoustic medium. In another example, a loudspeaker device includes a MEMS device, where the MEMS device at least includes: an ultrasonic source and a time-varying acoustic coupler; and a driving device that communicates with the MEMS device and is configured to operate the ultrasonic source and the time-varying acoustic coupler to generate an audio signal. In another example, the driving device at least includes a charge pump; a processor unit; a communication unit; two or more switches; where one switch connects the charge pump to a membrane, and a second switch connects the charge pump to a shutter; and the processor operates the switches to generate a modulated ultrasonic signal from the membrane and an audio signal from the shutter operation.

[0095] In an alternative example, a method for manufacturing a MEMS device includes the following steps: depositing a first dielectric material; using a first etching process that defines at least one cavity in the first dielectric; depositing a second dielectric mainly including an organic material; depositing a conductive material; and using a second etching process to remove at least a part of the second dielectric organic material under at least some of the conductive material. In another example, the first dielectric material includes any one of the following, but is not limited to the following: SiO2; SiOx; aSi; SiN; TiO2; alumina; AlN or a combination thereof. In another example, the second dielectric includes any one of the following, but is not limited to the following: polymers; polyamides; silicones; SU8; PMDS; PVDF; epoxy resins or a combination of these organic materials. In another example, the second etching process at least includes any one of the following, but is not limited to the following: oxide plasma; ozone plasma; CF4; CF6 or a combination of these etching processes. In another example, the conductive material at least includes any one of the following, but is not limited to the following: aluminum; nickel; silicon; polysilicon; copper; chromium; titanium or a combination of these conductive materials. In another example, after the second etching process, at least a part of the conductive material can move freely. In another example, a planarization step is applied after depositing the second dielectric. In another example, the method for manufacturing a MEMS device is applied to the manufacture of MEMS devices that require structural release. Examples of MEMS devices that require structural release include, but are not limited to: RF switches; micromirrors, accelerometers, gyroscopes, pressure sensors, barometers, inkjet dispensers, ultrasonic sensors, timing devices, temperature sensors, thermal imaging sensors, and bolometers.

[0096] In an alternative example, the loudspeaker device includes: a first diaphragm that vibrates at at least one of a first ultrasonic frequency; a second oscillating diaphragm that oscillates at at least a second ultrasonic frequency; and wherein at least one audio signal is generated at a frequency that is the frequency difference between the first ultrasonic frequency and the second ultrasonic frequency. In an alternative example, the loudspeaker device includes a first acoustic port; a second acoustic port; a first membrane; a second membrane; an acoustic medium connecting the first membrane and the second membrane; wherein the first membrane and the second membrane oscillate at ultrasonic frequencies; and the audio signal is generated in the first and / or second acoustic port by changing any one but not limited to the following: the phase between the oscillation of the first membrane and the oscillation of the second membrane; the oscillation amplitude of the first membrane; the oscillation amplitude of the second membrane; any combination of these changes. In another example, at least one acoustic port is in acoustic contact with a Helmholtz resonator having a resonance frequency below 1 KHz. In another example, the loudspeaker device includes at least one ultrasonic source that generates an audio-modulated acoustic radiation signal. In an alternative example, the loudspeaker device includes at least one ultrasonic source that is coupled to the acoustic medium through at least one time-varying acoustic coupler and generates an audio signal and at least one ultrasonic source that generates an audio-modulated acoustic radiation signal.

[0097] There is little difference between the hardware and software implementations of various aspects of the system; the use of hardware or software is generally (but not always, as in some cases the choice between hardware and software may become important) a design choice representing a cost-versus-efficiency trade-off. There are various vehicles (e.g., hardware, software, and / or firmware) that can implement the processes and / or systems and / or other technologies described herein, and the preferred vehicle will vary with the context in which the process and / or or system and / or other technology is deployed. For example, if the implementer determines that speed and accuracy are of utmost importance, the implementer can choose a vehicle that is primarily hardware and / or firmware; if flexibility is of utmost importance, the implementer can choose an implementation that is primarily software; or, alternatively, the implementer can choose some combination of hardware, software, and / or firmware.

[0098] The foregoing detailed description has set forth various embodiments of apparatuses and / or processes using block diagrams, flowcharts, and / or examples. Insofar as such block diagrams, flowcharts, and / or examples contain one or more functions and / or operations, it will be understood by those skilled in the art that each function and / or operation within such block diagrams, flowcharts, or examples can be implemented, individually and / or collectively, by a variety of hardware, software, firmware, or virtually any combination thereof. In one embodiment, several parts of the subject matter described herein may be implemented via an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), or other integrated formats. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein may be equivalently implemented, in whole or in part, in integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or virtually any combination thereof, and designing circuits and / or writing code for software and / or firmware would be well within the skill of those of skill in the art in light of this disclosure. Additionally, those skilled in the art will understand that the mechanisms of the subject matter described herein are capable of being distributed in a variety of forms as a program product, and that illustrative embodiments of the subject matter described herein apply regardless of the particular type of signal bearing medium used to actually effect such distribution. Examples of signal bearing media include, but are not limited to, the following: recordable type media such as floppy disks, hard disk drives, compact disks (CDs), digital versatile disks (DVDs), digital tapes, computer memories, and the like; and transmission type media such as digital and / or analog communication media (e.g., fiber optic cables, waveguides, wired communication links, wireless communication links, and the like).

[0099] Those skilled in the art will recognize that it is common in the art to describe devices and / or processes in the manner described herein and then integrate the described devices and / or processes into a data processing system using engineering practices. That is, at least a portion of the devices and / or processes described herein can be integrated into a data processing system via a reasonable amount of experimentation. Those skilled in the art will recognize that a typical data processing system generally includes one or more of the following: a system unit enclosure, a video display device, memories such as volatile and non-volatile memory, processors such as microprocessors and digital signal processors, computing entities such as operating systems, drivers, graphical user interfaces, and application programs, one or more interaction devices such as touchpads or screens, and / or a control system including feedback loops and control motors (e.g., for sensing position and / or speed feedback; for moving and / or adjusting components and / or amounts, control motors). A typical data processing system can be implemented using any suitable commercially available components, such as those commonly found in data computing / communication and / or network computing / communication systems.

[0100] The subject matter described herein is sometimes illustrated with different components contained within or connected to different other components. It should be understood that such described architectures are merely exemplary, and in fact, many other architectures that achieve the same functionality can be implemented. Conceptually, any arrangement of components that achieves the same functionality is effectively "associated" such that the desired functionality is achieved. Thus, any two components that are combined herein to achieve a particular functionality can be considered to be "associated" with each other such that the desired functionality is achieved, regardless of the architecture or intermediate components. Similarly, any two components so associated can also be considered to be "operably connected" or "operably coupled" to each other to achieve the desired functionality, and any two components that can be so associated can also be considered to be "operably coupleable" to each other to achieve the desired functionality. Specific examples of operably coupling include, but are not limited to, physically mating and / or physically interacting components and / or wirelessly interacting and / or wirelessly interacting components and / or logically interacting and / or logically interacting components.

[0101] Regarding the use of substantially any plural and / or singular terms herein, those skilled in the art can convert from plural to singular and / or from singular to plural according to the context and / or application. For clarity, various singular / plural permutations may be explicitly set forth herein.

[0102] Those skilled in the art will understand that, generally speaking, the terms used herein, especially in the appended claims (e.g., the subject matter of the appended claims), are generally intended to be "open" terms (e.g., the term "comprising" should be interpreted as "including but not limited to", the term "having" should be interpreted as "having at least", the term "includes" should be interpreted as "includes but not limited to", etc.). Those skilled in the art will further understand that if it is intended to refer to a specific number of introduced claim recitations, such intention will be expressly recited in the claims, and in the absence of such reference, there is no such intention. For example, for the purpose of helping understanding, the appended claims may contain the use of introductory phrases such as "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed as implying that the introduction of a claim recitation by the word "a" or "an" will limit any particular claim containing such introduced claim recitation to the disclosure of only one such recitation, even when the same claim includes the introductory phrase "one or more" or "at least one", the words such as "a" or "an" (e.g., "a" and / or "an" should generally be interpreted as meaning "at least one" or "one or more"); the same is true for the use of words used to introduce claim recitations. In addition, even if a specific number of introduced claim recitations are expressly recited, those skilled in the art will recognize that such recitations should generally be interpreted as being at least the recited number (e.g., a simple recitation of "two recitations", without further modifiers, generally means at least two recitations, or two or more recitations). In addition, in cases where a convention similar to "at least one of A, B, and C, etc." is used, generally speaking, such a structure is intended to be understood in the sense that those skilled in the art will understand the convention (e.g., "a system having at least one of A, B, and C" will include, but not be limited to, the following systems: A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In those cases where a convention similar to "at least one of A, B, or C, etc." is used, generally speaking, such a structure is intended to be understood in the sense that those skilled in the art will understand the convention (e.g., "a system having at least one of A, B, or C" will include, but not be limited to, the following systems: A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). Those skilled in the art will further understand that any disjunctive word and / or phrase that actually presents two or more alternative terms, whether in the specification, claims, or drawings, should be understood as contemplating the possibility of including one of those terms, any one of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibility of "A" or "B" or "A and B". The speaker and the micro speaker are interchangeable and can be used in place of the other.

[0103] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and not intended to be limiting, and the true scope and spirit are indicated by the appended claims.

Claims

1. A loudspeaker device, comprising: an acoustic medium; and at least one ultrasonic source, which includes a membrane coupled to the acoustic medium through at least one time-varying acoustic coupler, and the time-varying acoustic coupler includes at least a shutter and a baffle, and each of the shutter and the baffle is located near the membrane, wherein the shutter is configured to operate at a shutter resonance frequency, and the membrane is configured to operate at a frequency corresponding to the shutter resonance frequency, wherein the time-varying acoustic coupler is configured to be electrically activated to operate at the mechanical resonance of the time-varying acoustic coupler to generate an audio signal.

2. The loudspeaker device according to claim 1 further includes a Helmholtz resonator, wherein, The at least one ultrasonic source is in acoustic contact with the Helmholtz resonator at a resonance frequency below 1 KHz.

3. A loudspeaker device, comprising: an acoustic medium; at least one ultrasonic source, which includes a membrane containing a cavity and at least one source acoustic port, and is configured to generate an ultrasonic signal; and a time-varying acoustic coupler, which has an input acoustic port and an output acoustic port, and the time-varying acoustic coupler includes at least a shutter and a baffle, and each of the shutter and the baffle is located near the membrane, wherein the shutter is configured to operate at a shutter resonance frequency, and the membrane is configured to operate at a frequency corresponding to the shutter resonance frequency, wherein the source acoustic port of the ultrasonic source is connected to the input acoustic port of the time-varying acoustic coupler, and the output acoustic port of the time-varying acoustic coupler is connected to the acoustic medium; wherein the time-varying acoustic coupler is configured to be electrically activated to operate at the mechanical resonance of the time-varying acoustic coupler; and wherein the acoustic signal at the output acoustic port includes an audio signal.

4. The loudspeaker device according to claim 3, further comprising a Helmholtz resonator, wherein, The at least one ultrasonic source is in acoustic contact with the Helmholtz resonator at a resonance frequency below 1 KHz.

5. A loudspeaker device, comprising: a MEMS device, wherein the MEMS device includes at least an ultrasonic source containing a membrane, a shutter, and a time-varying acoustic coupler; and a driving device, which communicates with the MEMS device and is configured to operate the ultrasonic source and the time-varying acoustic coupler; wherein the time-varying acoustic coupler is configured to be electrically activated to operate at the mechanical resonance of the time-varying acoustic coupler and generate an audio signal, wherein the driving device includes at least: a charge pump; a processor unit; a communication unit; and two or more switches; wherein at least one switch connects the charge pump to the membrane, and at least a second switch connects the charge pump to the shutter; and wherein the processor unit operates the switches to generate a modulated ultrasonic signal from the membrane, and wherein the time-varying acoustic coupler is configured to be electrically activated to operate at the mechanical resonance of the time-varying acoustic coupler and generate an audio signal.

6. The loudspeaker device according to claim 5, further comprising a Helmholtz resonator, wherein, The ultrasonic source is in acoustic contact with the Helmholtz resonator at a resonance frequency below 1 KHz.

7. A loudspeaker device, comprising: an acoustic medium; a time-varying acoustic coupler; and at least one ultrasonic source, which is configured to generate an audio-modulated acoustic radiation signal; wherein the ultrasonic source is acoustically connected to the acoustic medium through the time-varying acoustic coupler; and Wherein, the time-varying acoustic coupler is configured to generate an audio signal based on the audio-modulated acoustic radiation signal.

8. The loudspeaker device according to claim 7, wherein, The time-varying acoustic coupler includes at least one moving membrane.

9. The loudspeaker device according to claim 7, wherein, The time-varying acoustic coupler operates at the mechanical resonance frequency of the time-varying acoustic coupler.

10. The loudspeaker device according to claim 7, further comprising a driving unit configured to provide an electrical signal for operating the time-varying acoustic coupler and the ultrasonic source.

11. A loudspeaker device, comprising: at least two membranes; and a driving unit including at least a charge pump and one or more switches; wherein, the driving unit is configured to connect the at least two membranes to the charge pump through the switches, and is configured to generate an audio signal by modulating an audio-modulated ultrasonic signal.

12. The loudspeaker device according to claim 11, wherein, The at least two membranes are configured as MEMS devices.

13. The loudspeaker device according to claim 11, wherein, At least one membrane operates at the mechanical resonance frequency of the membrane.

14. The loudspeaker device according to claim 11, wherein, At least one switch of the driving unit is configured to operate at a frequency consistent with the mechanical resonance frequency of the membrane.

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