Device for insertion into the ear canal of a mammalian subject

Abstract

A device for insertion into an ear canal of a mammalian subject comprises a body, a first adjustable acoustic-mechanical portion, a second adjustable acoustic-mechanical portion, and an adjustment device (204). The body has at least one sound path (252) extending therethrough. The first adjustable acoustic-mechanical portion comprises an adjustable channel (224) forming at least a portion of the sound path, and the second adjustable acoustic-mechanical portion comprises an adjustable membrane (210). The second adjustable acoustic-mechanical portion is acoustically arranged in series with the first adjustable acoustic-mechanical portion. The adjustment device is used to simultaneously adjust the first adjustable acoustic-mechanical portion and the second adjustable acoustic-mechanical portion to change the acoustic response of the at least one sound path.

Description

Technical Field

[0001] The present invention relates to ear protection for use, for example, in reducing the intensity of sound experienced by a user. Background Art

[0002] Exposure to high intensity noise can cause damage to a person's hearing. When a person is regularly exposed to loud noise, the damaging effects increase. In extreme cases, regular exposure to loud noise can lead to noise-induced hearing loss. Therefore, in order to protect hearing, the effects of continuous, intermittent and impact noise must be reduced. Due to the increasing awareness of the damaging effects of loud noise, for example from industrial sources, there are now various industry requirements for personnel to use ear protection. In many cases, personnel may be exposed to loud noise, for example when operating noisy machinery. A common form of noise protection that is widely used is earplugs, which reduce the intensity of the sound entering the human ear and therefore reduce the damaging effects of high intensity noise.

[0003] There are two main types of commonly used earplugs: passive earplugs and active earplugs. Passive earplugs attenuate all levels of sound intensity equally, that is, they provide a uniform attenuation level, for example, 20dB reduction, regardless of the sound intensity. Passive earplugs come in various forms, including: foam, silicon, flanged and custom molded earplugs. Passive earplugs are usually inserted into the user's ear canal. Passive earplugs use the material of the earplug itself to attenuate the sound passing through it. When the incident sound passes through the earplug, the sound is attenuated by the material of the earplug. Some sound will propagate through the earplug and pass out of the earplug into the air volume of the user's ear canal, where the sound will be detected by the user. The intensity of the sound will be reduced, and therefore the risk of damage to the user's hearing can be reduced. Unfortunately, however, such passive earplugs also change other characteristics of the sound, because the attenuation is usually frequency-dependent, and therefore the sound quality is usually reduced. For example, this can be a problem for musicians, because they need to hear high-fidelity sound to ensure that the sound they hear is actually the sound being played.

[0004] Furthermore, if they are properly inserted, the fixed attenuation level provided by passive earplugs is relatively high. As a result, users of passive earplugs must often remove them periodically in order to verbally communicate with coworkers. Depending on the noise level, the inconvenience associated with having to repeatedly remove and replace earplugs may result in reduced compliance with the requirement to wear earplugs in certain circumstances.

[0005] The above disadvantages can be overcome by using active earplugs including electronic components that enable the earplugs to attenuate high-intensity sounds while being relatively sound-transparent and providing only a low level of attenuation when the surrounding sounds have low intensity. Active earplugs typically include passive earplugs used in combination with a microphone on the outside of the earplug and a speaker on the inside of the earplug. Active earplugs typically listen to sounds outside the earplug and then replay them to the user through the speaker at a reduced intensity. Active earplugs can use control circuits to apply different levels of attenuation at different times or at different frequencies - called 'adaptive attenuation'. Some other systems include circuits that detect incident sounds and generate out-of-phase signals that destructively interfere with the incident sounds, thereby reducing the intensity of the incident sounds when the incident sounds propagate into the user's ear canal, which is generally referred to as "active noise cancellation". One disadvantage of active earplugs is that they are typically relatively expensive due to their electrical components. In addition, due to the need to constantly monitor and replay the detected sounds, active earplugs typically have relatively high power consumption. Summary of the invention

[0006] The present invention seeks to solve or alleviate the problems outlined above and according to a first aspect provides a device for insertion into the ear canal of a mammalian subject, the device comprising:

[0007] a body having at least one sound path extending therethrough;

[0008] a first adjustable acoustic-mechanical portion comprising an adjustable channel forming at least a portion of the sound path;

[0009] a second adjustable acoustic-mechanical portion arranged acoustically in series with the first adjustable acoustic-mechanical portion, the second adjustable acoustic-mechanical portion comprising an adjustable membrane; and

[0010] Adjustment means for simultaneously adjusting the first adjustable acoustic-mechanical portion and the second adjustable acoustic-mechanical portion to change the acoustic response of the at least one sound path.

[0011] Applicants have recognised that, through the claimed arrangement of adjustable channels and adjustable membranes, an acoustic response of a sound path can be achieved which does not significantly degrade the quality of the sound passing through the sound path whilst retaining the ability to control the sound, for example by attenuating the sound. This is because it allows for variations in the channel and membrane as the channel and membrane are adjusted to complement each other in maintaining a favourable acoustic response.

[0012] As will be understood by those skilled in the art, the acoustic response of a sound path should be understood as how the sound path affects the sound passing through it. The acoustic response of a sound path can change the frequency, amplitude and / or phase of the sound passing through it, and thereby ultimately change the sound heard by the user of the device.

[0013] It will be appreciated by those skilled in the art that the device according to the present invention advantageously does not necessarily require the presence of complex electronic circuitry contained in active earplugs, such as speakers to reproduce sound to the user, while maintaining the ability to control the sound, and thus avoiding the need to remove and replace the earplugs to adapt to changing sound environments. As a result, the device can have zero or very low power consumption compared to typical active earplugs. In addition, the device according to the present invention can advantageously maintain the quality of the sound passing through the device compared to purely passive earplugs.

[0014] The adjustment device may include any suitable device for adjusting the first adjustable acoustic-mechanical part and the second adjustable acoustic-mechanical part. In one set of embodiments, the adjustment device includes a first actuator for adjusting the first adjustable acoustic-mechanical part and a second actuator for adjusting the second adjustable acoustic-mechanical part. The first actuator and the second actuator may, for example, be connected to a single controller capable of simultaneously controlling each of the first adjustable acoustic-mechanical part and the second adjustable acoustic-mechanical part. Such an arrangement may be particularly advantageous when the first adjustable acoustic-mechanical part and the second adjustable acoustic-mechanical part need to be adjusted by different amounts, for example due to the need to achieve a specific acoustic response. If required in a particular situation, having a separate actuator for each adjustable acoustic-mechanical part can make it possible to adjust the other part by a larger proportion of its physical range of movement than one of the parts to achieve the desired response.

[0015] In an alternative set of embodiments, the adjustment device comprises a common actuator arranged to adjust both the first acoustic-mechanical part and the second acoustic-mechanical part simultaneously. Applicants have found that the use of such a common actuator may be advantageous, for example in embodiments where the device is electric, because it may reduce the amount of power required to adjust the first adjustable acoustic-mechanical part and the second adjustable acoustic-mechanical part. It may also simplify the construction of the device. Of course, by appropriate design of such an actuator, for example incorporating one or more levers or members of different stiffnesses, different amounts of movement may be imparted to the respective acoustic-mechanical parts for a given input movement.

[0016] In one set of embodiments the or each actuator comprises an electric motor. The use of an electric motor may advantageously mean that the device can automatically adjust the acoustic-mechanical portion without requiring physical input from the user. For example, the use of an electric motor may mean that the device can automatically adjust to attenuate sound in the presence of a noisy environment without requiring any action by the user, thereby helping to ensure that the sound path has an appropriate acoustic response for the acoustic environment in which the user is located, thereby protecting the user.

[0017] In another set of embodiments, the actuator or each actuator comprises a user operable member arranged to operate at least a portion of the adjustment device. The user operable member may directly drive the adjustment device. The user operable member may, for example, comprise a rotatable knob arranged to adjust the first adjustable acoustic-mechanical portion and the second adjustable acoustic-mechanical portion. Applicants have recognised that a user operable member arranged to operate a portion of the adjustment device may advantageously simplify the device and potentially reduce its cost. By using a user operable member, a device may be achieved that does not include any electrical / electronic components, thereby potentially providing a device that does not require power. The achievement of a device that does not require power may mean that the device is used more frequently because the user does not have to be concerned with ensuring that the device has sufficient battery power for operation. This helps to improve compliance with industrial requirements such as the use of hearing protection.

[0018] The first adjustable acoustic mechanical part including the adjustable channel can be adjusted in any suitable manner to achieve the desired acoustic response. In one set of embodiments, the adjustment device is configured to adjust the length of the adjustable channel. The applicant has recognized that adjusting the length of the adjustable channel can generally increase the effect of the channel. Additionally or alternatively, the adjustment device is configured to adjust the width of the adjustable channel. The applicant has found that adjusting the width of the adjustable channel can be used to adjust specific acoustic characteristics of the sound path. For example, reducing the width of the channel will generally increase the effective acoustic mass and acoustic loss of the channel, and vice versa. Conversely, reducing the length of the channel will generally reduce the effective acoustic mass and acoustic loss of the channel, and vice versa. In other words, the acoustic mass and loss generally have a positive relationship with the length of the channel and a negative relationship with the width of the channel. The terms acoustic mass and acoustic loss are well known to those skilled in the art, but will be further explained later.

[0019] It will be appreciated that the length and width of the adjustable channel may be adjusted independently of each other, or may be adjusted together at the same time. In a possibly overlapping set of embodiments, the adjustment means is configured to adjust the shape of the adjustable channel.

[0020] The adjustable channel may be defined by any suitable structure within the device. For example, the channel may simply include a cylindrical or other shaped channel extending through the body of the device. The adjustment of such a channel may, for example, include contracting and expanding the body to reduce / increase the size of the channel, or include providing contraction at the entrance or exit of the channel or along a portion of the channel. In one set of embodiments, the channel includes an adjustable barrier member. However, in another set of embodiments, the channel is defined by the space between the wall of the cavity in the body and the piston arranged in the cavity, wherein the adjustment of the channel is achieved by moving the piston relative to the cavity. The cross section of the channel will depend on the shape of the cavity wall and the outer profile of the piston. The piston may have a cross-sectional shape complementary to the wall of the cavity, for example, if the wall has a circular cross-sectional shape, the piston may have a circular cross-sectional shape. In such an example, the channel defined between the wall and the piston is actually an elongated annular channel. The applicant has recognized that the arrangement of the piston in the cavity provides a relatively simple member to adjust the length and / or cross-sectional area and / or shape of the channel.

[0021] The piston can be arranged in the device in any suitable manner so that it can move relative to the cavity. For example, the piston can be part of a linear actuator that can move the piston in and out of the cavity, or can be attached to the linear actuator. In one group of embodiments, the piston is arranged to move axially in the cavity, and the device includes at least one elastic member, which is arranged to bias the piston out of the cavity, wherein the regulating device includes an actuating member, which is arranged to drive the piston axially into the cavity against the elastic bias. The actuating member can be driven by a motor or a user-operable member. The applicant has recognized that providing an elastic member arranged in a manner according to the above embodiment group means that the actuating member only needs to be able to drive the movement in one axial direction because the elastic member is arranged to drive the movement of the piston in another axial direction. This can simplify the manufacture and construction of the device. In one group of embodiments, the actuating member is arranged to rotate relative to the piston, and the device further includes a device for converting the rotational movement of the actuating member into the axial movement of the piston. The elastic member can be arranged integrally with the piston. In another set of embodiments, a plurality of resilient members are provided.In another set of embodiments, the at least one resilient member is in the form of a resilient arm extending between the piston and the body.

[0022] In another set of embodiments, the piston includes a threaded portion that is arranged to engage with a threaded portion on the body so that rotation of the piston causes linear movement of the piston within the cavity. Such a set of embodiments may utilize a motor to drive the movement of the piston, or utilize a user-operable member. As will be appreciated by those skilled in the art, the pitch of the threaded portion may be selected to allow highly controlled movement of the piston within the cavity. Such control may be required in order to precisely control the acoustic response of the adjustable channel. The threaded engagement between the piston and the body, and in particular the static friction generated between the threaded portions, may also mean that the piston is held in its position without the need for action from another component such as a motor. This may mean that once the piston has moved to its desired position, any power supplied to, for example, a motor may be turned off. This helps to reduce the power consumption of the device.

[0023] Of course, in addition or as an alternative, the piston may be arranged to move in other directions than the axial direction alone. For example, the piston may move at a non-zero angle relative to the axis, translate from side to side within the cavity or even twist in order to adjust the passage to achieve a desired acoustic response.

[0024] In one set of embodiments, the piston is arranged so that it can be stably maintained in a plurality of different positions in the cavity. This may be achieved, for example, due to the presence of static friction, as described above with respect to the embodiment in which the piston includes a threaded portion. Alternatively, the device may include different means for maintaining the piston stable. For example, the piston and the body may each include a series of recesses and corresponding protrusions that act to maintain the piston stable when the recesses and protrusions engage each other.

[0025] Applicants have recognized that in order to properly control the acoustic response of the sound path, it may be necessary to adjust both the length and cross-section of the adjustable channel. In another set of embodiments, the cavity and the piston each have a frustoconical shape, so that the adjustable channel has the form of a frustoconical shell. Applicants have recognized that in such an arrangement, the axial movement of the piston in the cavity can simultaneously adjust the length and width of the channel. This can also mean that relatively large axial movement can be converted into relatively small width changes. This can help to simplify the manufacture and construction of the device and provide fine control over the width. The piston and cavity are preferably shaped so that the channel maintains a uniform shape throughout the entire stroke of the piston, but this is not necessary.

[0026] As mentioned above, a common actuator can be provided to adjust the adjustable channel and the adjustable membrane at the same time. Such common actuation can be implemented in a variety of ways. In an embodiment including a piston, in another group of embodiments, the piston is arranged so that the movement of the piston adjusts the tension of the membrane. The piston can be connected to the membrane to adjust the tension of the membrane in any suitable manner. For example, the piston can extend through the cavity and be directly connected to the membrane, for example, it can physically contact the membrane directly to deform the membrane. However, in one group of embodiments, the piston is connected to an elastic member, which is arranged to act on the membrane or a part of the body to which the membrane is attached. Those skilled in the art will understand that the arrangement of the elastic member acting between the piston and the membrane can reduce the movement of the piston and its influence on the membrane in proportion. For example, the elastic member can convert the millimeter movement of the piston into a micrometer movement relative to the membrane. Depending on the piston and the membrane, this may be necessary to achieve the desired acoustic response of the channel. The elastic member can be integrally formed as a part of the body or the piston, or alternatively, it can be a separate independent component.

[0027] The resilient member may be provided by any suitable member. However, in one set of embodiments, the resilient member comprises a central portion coupled to the piston and a plurality of legs extending from the central portion, the plurality of legs being arranged to act on the membrane or a portion of the body to which the membrane is attached. Applicants have recognised that such a resilient member comprising a plurality of legs may more evenly distribute the force applied to the membrane, which may result in a more even adjustment, e.g. tensioning, of the membrane.

[0028] In embodiments where the piston is in physical contact with the membrane to deform and thereby adjust the tension in the membrane, Applicants have noted that the level of attenuation provided by the device increases significantly when the piston first contacts the membrane, and will increase rapidly thereafter, even with smaller movements, compared to the level of attenuation provided when the piston is not in contact with the membrane. Applicants have recognized that this effect is undesirable, but that it may be reduced in some embodiments by including a compressible portion in the piston. Therefore, in one set of embodiments, the piston includes a compressible portion.

[0029] When the adjustable member contacts the membrane, the compressible portion of the adjustable member is compressed (and / or deformed), thereby reducing the force applied by the adjustable member on the membrane and causing a smaller increase in the tension of the membrane. Therefore, compared to a rigid piston (i.e., without a compressible portion), the level of attenuation provided by the device when the piston contacts the membrane can be increased more smoothly and gradually to allow for finer control of the attenuation provided by the device.

[0030] The compressible portion may be provided by any part of the piston, but in one set of embodiments the compressible portion of the piston contacts the surface of the membrane. This may contribute to the stability of the piston.

[0031] The piston may be arranged to have any suitable and desired shape. The piston may include a portion located within the channel and another portion extending from the channel to contact the membrane. There may be some embodiments in which the compressible portion (including a portion of the piston) does not have the same shape as the rest of the piston. For example, the compressible portion may be a cylinder having a smaller diameter than the rest of the piston.

[0032] The compressible portion of the piston may be shaped to be compressible (e.g., include a spring) and / or the compressible portion may be formed from a layer of an inherently compressible material. Preferably, the compressible portion of the piston is formed from an elastically compressible material. Although applicants have recognized that the piston may be formed from any suitable and desired compressible material, in one set of embodiments, the deformable portion is formed from a thermoplastic elastomer or a foam material such as polyurethane foam.

[0033] In one set of embodiments, the piston or the remainder of the piston other than the compressible portion is formed of a rigid material. Although the applicant has recognized that the piston can be formed of any suitable and desired material, preferably the piston is formed of plastic. For example, the piston is formed of a rigid plastic, such as polycaprolactam (PA6), acrylonitrile-butadiene-styrene (ABS) or polyoxymethylene (POM).

[0034] In one set of embodiments, the piston comprises a central axis perpendicular to the plane or at least the central section of the membrane. In one set of embodiments, the piston is rotationally symmetric about the central axis. This may help ensure that a uniform force is applied to the membrane when the piston contacts the membrane.

[0035] The piston may be in contact with the membrane throughout its travel. However, in one set of embodiments, the piston has a position in which the piston is not in contact with the membrane. In this position, the piston does not exert a force on the membrane, and therefore, the piston does not change the tension of the membrane from a base value.

[0036] It will be appreciated by those skilled in the art that the base level of attenuation provided by the device when the piston is in the non-contact position is lower than the level of attenuation provided by the device when the piston is in contact with the membrane. This is because when the piston is in contact with the membrane, the tension in the membrane increases and therefore the attenuation of sound by the membrane increases. However, the measures provided in accordance with the invention mean that, as previously described, the dramatic change in performance between non-contact and contact is much smaller than would otherwise be the case.

[0037] In one set of embodiments, the piston has multiple positions in which the piston contacts the membrane. The multiple positions of the piston correspond to multiple magnitudes of force applied to the membrane, and therefore multiple tensions in the membrane. For example, as the piston moves further toward the membrane, the piston applies a greater force on the membrane, and therefore the tension in the membrane increases. Thus, the attenuation of the membrane is greater, and the device provides a higher level of attenuation.

[0038] The acoustic response of the at least one sound path may additionally be altered by providing a barrier member.

[0039] In one set of embodiments, the barrier member comprises an adjustable closure, for example a cover that can be arranged as a hinge or slide. Preferably, the barrier member has at least an open position and a closed position. In the open position, sound can be transmitted through the device as described above, i.e. relatively attenuated by the barrier member. In the closed position, sound can be substantially attenuated by the barrier member.

[0040] The barrier member may be configured to provide a plurality or succession of different positions, for example between an open position and a closed position.

[0041] The membrane can be in the form of a relatively thin sheet of material arranged on or in the device, and can have any suitable shape, such as a circle. In one set of exemplary embodiments, the membrane is made of a low-density plastic film such as polyethylene terephthalate. The applicant has recognized that a circular membrane can allow a more uniform adjustment of the membrane, such as tensioning of the membrane, when compared with a membrane with an alternative shape such as a square membrane. The membrane can be integral with the body. For example, the membrane can be integrally molded with the body, or the body can be ground to form the membrane. However, the applicant has recognized that it may be more complicated to provide the membrane integrally with the body. In one set of embodiments, the membrane is a separate component attached to the body. In another set of embodiments, the body defines a circumferential edge to which the membrane is attached. This can allow a simpler manufacture of the body. In addition, it can allow the body and the membrane to be made of different materials, which is necessary for providing a sound path with a desired acoustic response. In an embodiment including an elastic member, the elastic member can act on the edge to adjust the tension on the membrane. Such an arrangement allows the membrane to be adjusted without directly acting on the membrane.

[0042] In one set of embodiments, the membrane comprises at least one corrugation. Applicants have recognised that by implementing a tensioned membrane comprising at least one corrugation, a finer control over the attenuation provided by the device may be achieved, particularly in embodiments where the piston is arranged to contact the membrane. When the piston contacts the membrane, the corrugations are typically (at least partially) stretched due to the force applied by the piston on the membrane, and for a given applied force, a smaller increase in tension in the membrane may be observed. Thus, the level of attenuation provided by the device may be increased more gradually when the piston contacts the membrane, compared to a membrane without any corrugations. Thus, this may provide a similar effect to providing a piston with a compressible portion, and may be implemented in lieu of or in conjunction with that feature when the piston contacts the membrane.

[0043] In one set of embodiments, the corrugations comprise ridges. In one set of embodiments, which may overlap, the corrugations comprise notches. Depending on the orientation of the film, the same corrugation may be described as a ridge or a notch. Preferably, the maximum height of the ridges above the plane of the film or the depth of the notches below the plane of the film is in the range of 0.02 mm to 2 mm, such as 0.1 mm to 1 mm, such as 0.3 mm.

[0044] In one set of embodiments the corrugations are arranged on the membrane so that the piston does not contact the corrugations.The piston may deform the corrugations by applying a force to another part of the membrane which is transmitted to the corrugations.

[0045] In one set of embodiments, the piston is arranged to contact the membrane at the geometric center of the membrane. In such embodiments, and when the membrane is circular, the corrugations may be arranged on the membrane at a distance from the geometric center of the membrane in the range of 30% to 90% of the radius of the membrane.

[0046] In one set of embodiments, the corrugations are circular and centred on the geometric centre of the membrane. The ridges or indentations preferably have a uniform cross section (e.g. a circular corrugation has a constant cross section over the entire circumference of the formed circle) so that the corrugations are uniformly deformed by the piston. This may help to ensure that the quality of the sound is not significantly degraded by the device.

[0047] In one set of embodiments, the membrane comprises a plurality of corrugations. Different corrugations or different subsets of corrugations within a plurality of corrugations may have different shapes and sizes. However, preferably, the plurality of corrugations all have the same shape. Corrugations of uniform shape may deform similarly under the same force. Thus, implementing a plurality of uniform corrugations (particularly in combination with a uniform corrugation arrangement on an adjustable membrane) may help to smoothly and predictably vary the horizontal attenuation of the device.

[0048] Applicants envision a particular arrangement in which the plurality of corrugations includes a subset of circular ridges and a subset of circular notches, which may be centered about the geometric center of the membrane. The various circular notches and ridges will have various diameters and may therefore be arranged at various distances (i.e., positions) from the geometric center of the adjustable membrane. For example, if the innermost circular corrugation is a notch, the second innermost circular corrugation is a ridge, the third innermost circular corrugation is a notch, etc., then the circular notches and ridges may be arranged alternately.

[0049] In an embodiment comprising a user operable member to operate at least a portion of the adjustment device, when the user hears or expects to hear a particular type of sound, they can operate the user operable member to adjust the adjustment device and thereby change the acoustic response of at least one sound path. Such a set of embodiments may be suitable for implementing a relatively inexpensive device. However, in a set of embodiments, the device further comprises a controller, which is arranged to control the adjustment device so as to change the acoustic response of the at least one sound path. The inclusion of a controller may allow the device to control the adjustment device in a more complex manner so as to provide the most appropriate acoustic response of the sound path. For example, it may achieve the highest sound quality while providing the necessary amount of attenuation. The controller may include a series of other components connected to it or provided integrally with it, such as a microphone or a transceiver. Such a set of embodiments may also advantageously automatically adjust the acoustic response of the sound path based on the detected sound environment in which the device is located. Additionally or alternatively, the device may include a user input, such as in the form of at least one button, which enables the user to control the operation of the device. This may, for example, allow the user to select a specific operating mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Certain preferred embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

[0051] Figure 1 shows an isometric view of an apparatus according to an embodiment of the present invention;

[0052] Figure 2 Shows Figure 1 A view of the underside of the device as seen in;

[0053] Figure 3 Shows Figure 1 An exploded view of the device seen in;

[0054] Figures 4a to 4b Independently shows the formation Figure 1 an actuating member as part of a device;

[0055] Figure 5 The formation is shown separately Figure 1 A piston as a part of the device seen in;

[0056] Figure 6 Shown separately Figure 1 a portion of the body of the device as seen in;

[0057] Figure 7 Shows Figure 1 A portion of the body of the device as seen, as well as the membrane;

[0058] Figures 8a to 8bis a diagram showing how the relative position of the piston in the cavity regulates the passage;

[0059] Figures 9a to 9b is a diagram showing how to adjust the tension on the membrane;

[0060] Figures 10a to 10b Shows Figure 1 A cross-sectional view of the device in an open configuration as seen in;

[0061] Figures 11a to 11b Shown in Figure 1 A perspective view of the device in a closed configuration as seen in ;

[0062] Figures 12a to 12b shows a cross-sectional view through the device in a closed configuration;

[0063] Fig.13 shows a perspective view of a device according to a second embodiment of the present invention;

[0064] Figures 14a to 14b Shows Fig.13 A cross-sectional view of the device in an open configuration as seen in;

[0065] Figures 15a to 15b Shown in Fig.13 A cross-sectional view of the device in a closed configuration as seen in;

[0066] Fig.16a shows an isometric view of a portion of a hearing protection device according to a third embodiment of the present invention;

[0067] Fig.16b Shows Fig.16a Alternative isometric view of the device seen in ;

[0068] Fig.17a Shows Fig.16a An exploded view of the parts of the device as seen in ;

[0069] Fig.17b Shown in Fig.16a A separate isometric view of the body of the device as seen in;

[0070] Fig.18 Shows Fig.16a The piston, user operable member and membrane of the device as seen in;

[0071] Fig.19 Shows Fig.16a Separate isometric views of the piston and user operable members of the device as seen in;

[0072] Fig. 20 Shows Fig.16aA cross-sectional view of certain components of the device as seen in a first configuration;

[0073] Fig.21 Shows Fig.16a a cross-sectional view of certain components of the device as seen in a second configuration;

[0074] Fig. 22 Shows Fig.16a a cross-sectional view of certain components of the device as seen in FIG. 1 in a third configuration;

[0075] Fig.23 Shows Fig.16a Another view of the device as seen in the first configuration;

[0076] Fig.24 Shows Fig.16a Another view of the device as seen in the second configuration;

[0077] Fig.25 Shows Fig.16a Another view of the device as seen in FIG. 1 in a third configuration;

[0078] Figures 26a to 26b showing a cross-sectional view of an apparatus according to a fourth aspect of the invention; and

[0079] Fig. 27 is a graph showing the frequency response of an embodiment of the present invention compared to the frequency response of some prior art earplugs. DETAILED DESCRIPTION

[0080] Figure 1 An isometric view of a device according to an embodiment of the invention is shown. The device comprises a body 2 which includes a first adjustable acoustic-mechanical part in the form of an adjustable channel 4. The channel 4 is defined by the space between the walls of a cavity 6 and a piston 8 extending into the cavity 6. The piston 8 is arranged to move axially within the cavity 6 and is mounted to the body 2 by four resilient arms 10 which are received in suitably shaped arm receiving portions 12 provided on the body 2. The piston 8 further comprises a ridge 14, the purpose of which will become apparent from the discussion of the figures later.

[0081] The device further comprises an actuating member 16, which forms a part of an adjusting device, and the adjusting device is arranged to move the piston 8 axially in the cavity 6. The actuating member 16 comprises a cylindrical boss 20 for rotatably mounting the actuating member 16. The cylindrical boss 20 is accommodated in a socket (not shown) of an appropriate shape. The actuating member 16 comprises a set of two inclined cam surfaces 22, one of which can be seen in the figure. The other cam surface 22 is arranged to be opposite to the cam surface 22 seen in the figure. The cam surface 22 interacts with the ridge 14 on the piston 8, and the ridge is used as a follower for converting the rotation of the actuating member 16 into the axial movement of the piston 8. This will be described in more detail below. The actuating member 16 further comprises an actuating portion 24, which can be acted on to drive the rotation of the actuating member 16. This actuating portion 24 can be directly acted on by a user, for example. Therefore, in this embodiment, the actuating member 16 comprises an integrated user-operable member. Of course, as will be appreciated by those skilled in the art, the actuation member 16 may alternatively be driven by an electric motor.

[0082] Figure 2 Shows Figure 1 A view of the underside of the device as seen in FIG. 2 . At the base of the body 2 a second adjustable acoustic-mechanical part in the form of an adjustable membrane 26 is arranged. The adjustable membrane 26 is bonded to an edge 28 of the body 2 .

[0083] Figure 3 Shows Figure 1 . Starting from the top, the actuating member 16 and the piston 8 are shown. In this particular embodiment, the body 2 has a two-part construction including a first part 2a and a second part 2b, but it will be appreciated that a one-part construction may be used instead. The two parts are fixed together using any suitable means, such as gluing. Also shown in the figure is a resilient member 30 acting between the piston 8 and the second part 2b of the body 2. The piston 8 includes a cylindrical protrusion 32, which is arranged to be received in a circular hole 34 on the resilient member 30, thereby coupling the piston 8 and the resilient member 30. As will be appreciated by those skilled in the art, when the cylindrical protrusion 32 is received in the circular hole 34 of the resilient member 30, when all components of the device are assembled, the axial movement of the piston 8 downward into the cavity 6 will act to compress the resilient member 30.

[0084] The resilient member 30 includes a plurality of resilient legs 36 extending in a spiral manner away from the circular hole 34. When assembled, the resilient legs 36 engage with an inner flange 38 on the second portion 2b of the body 2. The membrane 26 is bonded to the second portion 2b of the body 2, such as Figure 2 shown.

[0085] Figure 4a and4b 1 and 2. The views of the actuating member 16 are shown separated from the other components of the device. The inclined cam surface 22 can be seen more clearly in these figures. Figure 4b A view of the underside of the actuation member 16 is shown and illustrates the presence of two cam surfaces 22 on the underside of the actuation member 16 .

[0086] Figure 5 An isometric view of the piston 8 is shown separated from the other components of the device. The lowest part 40 of the piston 8 extends into the cavity 6 when the device is assembled, and is frustoconical and has a shape corresponding to the cavity 6 (see FIG. Figure 6 ). As will be appreciated by those skilled in the art, the cavity 6 having complementary frustoconical shapes and the lowest portion 40 of the piston 8 form an annular channel 4 having a uniform shape and a diameter that decreases along its length. The ridge 14 extends linearly along the top of the piston and is arranged to interact with the cam surface 22 on the actuating member 16 seen in the previous figures.

[0087] Figure 6 An isometric view of the upper portion 2a of the body 2 is shown in isolation. In this figure it can be seen more clearly how the cavity 6 has a frustoconical shape. A hole 42 is at the base of the cavity 6 through which at least a portion of the piston 8 can extend. This hole 42 allows at least the cylindrical protrusion 32 on the piston 8 to pass through the cavity 6 and interact with the resilient member 30. The hole also allows sound to pass more freely through the cavity 6 into the rest of the device.

[0088] Figure 7 A view of the underside of the lower part 2b of the body 2 and the membrane 26 is shown. Figure 3 The inner flange 38 of the lower portion 2b of the body 2 as seen in the figure also defines an outer edge 28 to which the membrane 26 is bonded when the assembly is assembled. As will be appreciated by those skilled in the art, the outer edge 28 is relatively large when compared to the size of the membrane 26 and therefore provides a relatively large surface area on the lower portion 2b of the body 2 to bond the membrane 26 thereto. This can help ensure that the membrane 26 is securely bonded to the lower portion 2b of the body 2.

[0089] Figures 8a to 8b is a diagram showing how the position of the piston 8 in the cavity 6 can be used to adjust the passage 4. Figure 8a In the position as seen in FIG. 4 , the channel 4 has a length indicated by arrow 46 and a width indicated by arrow 48. Figure 8bAs shown, when the piston 8 moves axially into the cavity 6, the length of the channel indicated by arrow 46 and the width of the channel indicated by arrow 48 both change. Therefore, changing the axial position of the piston 8 relative to the cavity 6 will adjust the channel 4. As will be appreciated by those skilled in the art, adjusting the size of the channel 4 will serve to change the acoustic response of the channel 4, and therefore the acoustic response of the sound path. More specifically, the width d of the channel is related to the acoustic loss and acoustic quality of the channel. Under circuit simulation familiar to those skilled in the art for analyzing acoustic systems, the acoustic loss is equivalent to the resistance R and has an inverse cubic relationship with the channel width, as shown below:

[0090]

[0091] where k1 is a constant representing parameters that are assumed to remain constant, such as air density and dimensions.

[0092] Under the same electrical simulation, the acoustic mass is equivalent to the inductance L and has an inverse relationship with the channel width d:

[0093] where k2 is a constant representing parameters that are assumed to remain constant, such as air density and size.

[0094] Both resistance R and inductance L are proportional to the length of the channel.

[0095] Figures 9a to 9b is a diagram showing how to adjust the tension of the membrane 26. Figure 9a The membrane 26 is shown under a first tension, which for illustration purposes may correspond to the piston 8 being in a Figure 8a The membrane 26 extends between the flanges 26 and has a length 50 extending between the corners 39 of the flanges 38. Figure 9b As shown, when a force is applied to the flange 38, it will cause the flange to bend. When the flange 38 bends, the corners 39 move away from each other, thereby stretching the membrane 26. This can be seen that Figure 9b The length 50 between the corners 39 of the middle flange 38 is greater than Figure 9a The length of the membrane. Following the electrical simulation described above, when the membrane is stretched, the acoustic capacitance will decrease. Since this capacitance is in series with the acoustic capacity of the ear canal, and in series with the resistance and inductance of the transmission path through the channel, this will result in increased attenuation, but will also change the frequency response. According to the present invention, the changes in acoustic resistance, inductance and capacitance can be tuned so that the changes in frequency response match the natural frequency response of the human ear, so that the spectrum perceived by the user is essentially flat, as described below with reference to Fig.16a and Fig.16b What I see.

[0096] The device seen in the preceding figures may form part of a device that is inserted into the ear canal of a mammalian subject. For example, the device may be embedded in an insert of foam or other suitable material that is shaped to be inserted into the ear canal of a mammalian subject. The insert may be a standard insert that fits a variety of different ear shapes, or alternatively, it may be a custom molded insert that is dedicated to a particular user.

[0097] Now refer to Figure 1 9 describe the operation of the device. In use, when inserted into the ear of a mammalian subject, the device is arranged so that the membrane 26 is close to the user's eardrum and the actuation member 16 protrudes outwardly from the user's ear. This is not essential to the present invention, and other embodiments can be envisioned in which the order of the channels and membranes is reversed. Thus, sound will pass through the channel 4 and then through the membrane 26 into the user's ear canal.

[0098] The actuating member 16 can be used to control the position of the piston 8 and simultaneously adjust the tension on the membrane 26 so as to control the acoustic response of the sound path through the device. Since the actuating member 16 is maintained in a fixed axial position, when the actuating member 16 is rotated, the cam surface 22 acts on the ridge 14, thereby forcing the piston 8 axially downward into the cavity 6. Since the resilient arm 10 is received in the receiving portion 12 on the body 2, the piston 8 is prevented from rotating. The resilient arm 10 also allows the piston 8 to move axially downward into the cavity 6. As will be appreciated by those skilled in the art, as the piston 8 moves into the cavity 6, the length of the passage 4 will increase and its cross-section will decrease, as previously described. Figures 8a to 8b as shown in .

[0099] Furthermore, when the piston 8 moves into the cavity 6, the piston will also act to compress the resilient member 30 due to the engagement between the piston 8 and the resilient member 30. When the resilient member 30 is compressed, it will apply a force to the flange 38, causing it to deform in a manner that results in an increase in tension on the membrane 26. This Figures 9a to 9b Shown in.

[0100] Adjusting the length and cross-sectional area of ​​the channel 4, and adjusting the tension of the membrane 26, changes the acoustic response of the sound path through the device. Changing the acoustic response of the sound path will change the sound heard by the user of the device. As will be appreciated by those skilled in the art, with this embodiment, the piston 8 can be driven to any of a number of positions between the channel 4 being in a fully 'open' position and the channel being in a fully 'closed' position. Fig.10a and 10b The device is shown with the piston in the fully open position, and Fig.11a , 11b , 12a and 12b show the device with the piston in the fully closed position. This changes the acoustic resistance, inductance and capacitance as previously described.

[0101] Fig.10a and 10b The piston 8 is shown in Figure 1 As seen, a cross-sectional view of the device in the fully open position, wherein Fig.10a shows a side view of the device, and Fig.10b An isometric view of the device is shown. Arrow 52 indicates the path of sound through the device. As can be seen in each of these figures, sound enters the device and passes through channel 4. The sound can freely pass through the gap between the legs 36 on the elastic member 30. The sound then propagates towards the membrane 26 and passes through the membrane. These figures also show more clearly how the channel 4 has a frustoconical shell shape due to the frustoconical cavity 6 and the frustoconical piston 8.

[0102] Fig.11a and 11b Two different isometric views of the device in a second 'closed' configuration are shown. In this configuration, the actuating member 16 has been rotated relative to the body 2 to drive the piston 8 downwardly by the maximum amount. As the piston 8 moves downwardly, the resilient arm 10 deforms to allow such movement. Fig.11b As can be seen most clearly in FIG. 1 , the actuating member 16 has rotated a sufficient amount so that the inclined cam surface 22 has moved past the ridge 14 on the piston 8 and the ridge 14 now abuts the flat portion 54 on the actuating member 16. As will be appreciated by those skilled in the art, once the ridge 14 abuts the flat portion 54, it cannot be driven downward further.

[0103] Fig.12a and 12b A cross-sectional view of the device in a closed position is shown. The piston 8 has moved downwards to a position in which the passage 4 is completely closed. In this position, sound 52 will no longer be able to pass through the passage 4, and the device can completely or at least substantially prevent any sound from passing.

[0104] With reference to the previous figures, it will be appreciated by those skilled in the art that when it is desired to at least partially reopen the passage 4, the user can rotate the actuating member 16 in the opposite direction. The resilient arm 10 will deflect the piston 8 axially upwards from the cavity 6 so as to reopen the passage 4. Of course, due to the coupling between the piston 8 and the membrane 26 via the resilient member 30, when the piston 8 moves axially upwards, it will gradually release the tension on the membrane 26.

[0105] Fig.13 An isometric view of a device according to a second embodiment of the invention is shown.The device comprises a body 102 comprising an upper portion 102a and a lower portion 102b.

[0106] Fig.14a Shows Fig.13 The device includes a number of Figure 1 1, including a passage 104 defined by the space between the cavity 106 and the piston 108. The membrane 126 is bonded to the base of the lower body 102b. The resilient member 130 is arranged between the membrane 126 and the piston 108. The resilient member 130 is the same as the resilient member 30 described above. Similar to the previous embodiment, the resilient member 130 acts on the internal flange 138.

[0107] The device according to this embodiment Figure 1 The difference from the first embodiment seen in is that the piston 108 is rotatably mounted in the body 102. The piston 108 includes an external thread 156 that engages with a corresponding threaded portion 158 on the body 102. Therefore, as will be understood by those skilled in the art, when the piston 108 is rotated, it is advanced into the cavity 106 or withdrawn from the cavity. The direction of rotation of the piston 108 will indicate whether it is advanced into the cavity 106 or withdrawn from the cavity. A rectangular slot 160 is provided on the top of the piston 108. A drive shaft (not shown in this figure), for example connected to a motor, can be inserted into the slot 160 to drive the rotation of the piston 108. In Fig.14a In the view seen in , the device is in an 'open' configuration, in which the sound path 152 is open to allow sound to pass through the device.

[0108] Fig.14b A cross-sectional view of a device according to a second embodiment is shown, seen from the side.A motor 162 and a drive shaft 164 inserted into the slot 160 may be used to drive the rotation of the piston 108 and thus advance it into the cavity 106 and withdraw it from said cavity.

[0109] Fig.15a and 15b A cross-sectional view of the device in a 'closed' configuration is shown, with the motor 162 and drive shaft omitted. In this configuration, the piston 108 has been advanced into the cavity 106 so that the channel 104 is now closed. As a result, sound can no longer pass through the channel 104, and the device will therefore significantly attenuate any incident sound. Although not visible in these figures, in this configuration, the resilient member 130 will be pressed against the internal flange 138 and thus cause the tension on the membrane 126 to increase.

[0110] Of course, as will be appreciated by those skilled in the art, the piston 108 may be moved to Figures 14a to 14b and any intermediate position between the open and closed positions seen in 15a to 15b so as to achieve the desired acoustic response of the sound path.

[0111] Fig.16aAn isometric view of a portion of a hearing protection device according to a third embodiment of the present invention is shown. Fig.16a As shown, the device 201 comprises a body 202 on which a user operable member in the form of a handle member 204 is located.

[0112] The device 201 further includes a resiliently compressible member 214 located on the handle member 204. The resiliently compressible member 214 is arranged to apply force to various components of the device 201 to maintain the handle member 204 and the body 202 in a proper position relative to each other, for example, when the handle member 204 is rotated. The resiliently compressible member 214 can be compressed to different degrees.

[0113] Fig.16b Shows Fig.16a An isometric view of the underside of the device shown in FIG. Circular membrane 210 is arranged toward the base of device 201. Although Fig.16b The film is shown as transparent, but this is not required and the film may be opaque. The film is attached to the body 202 of the device, and in particular is bonded to a circular edge 222 (eg, Fig.17a shown).

[0114] from Fig.16b As can be seen in the figure, the handle member 204 is integrally formed with the piston 206, and the piston includes a compressible portion 208 at its distal end, which is in the form of a compressible material disc, such as a closed-cell foam or a thermoplastic elastomer. As will be explained later, the compressible portion 208 is arranged to contact the membrane 210 to increase the tension of the membrane 210. The piston 206 is attached to the handle member 204 by three spokes 226 extending from the circumference of the handle member 204 to the piston 206, so that the movement of the handle member 204 causes the movement (e.g., adjustment) of the piston 206. The movement of the piston 206 changes the degree of compression of the compressible member 214.

[0115] The handle member 204 is rotatable relative to the body 202 of the device 1. Specifically, the user can move the handle member 204 to a variety of different rotational positions relative to the body 202 of the device. When the handle member 204 rotates, the piston 206 also rotates. The conversion of the rotational movement of the handle member 204 to the axial (linear) movement of the piston 206 will be referred to Figures 20 to 25 More details will be discussed. Figures 20 to 25 As discussed in further detail, different rotational positions of handle member 204 correspond to different attenuations provided by device 201 .

[0116] The membrane 210 further includes corrugations 212. Fig.18 The ripple 212 can be seen more clearly in Fig.18 Shows Fig.16aAn isometric view of the individual handle members 204 and membrane 210 of the device shown. The corrugations 212 are circular ridges centered about the geometric center of the membrane 210 that extend above the plane of the membrane 210. This arrangement of the corrugations 212 means that the compressible portion 208 does not contact the corrugations 212 (e.g., the compressible portion 208 contacts the membrane 210 at the geometric center of the membrane 210). The cross-section of the ridges resembles a bell curve, which can be seen in FIG. Figures 20 to 22 More clearly seen in the cross-sectional view.

[0117] Fig.17a Shows Figure 1 An exploded view of the device as seen in . Starting from the top, Fig.17a The resiliently compressible member 214 and the handle member 204 are shown. The handle member 204 is substantially circular with a protruding gripping portion. As previously described, the handle member 204 is integrally formed with the piston 206. The piston 206 extends below the handle member 204 and is concentric therewith. Fig.17a Also shown is a tensioned membrane 210 including the corrugations 212 described above.

[0118] exist Fig.17a 2, a rim 222 can be seen which forms part of the body 202 of the device 1. The membrane 210 is fixed in place on the rim 222 by means of a stabilizing ring 216 and two tape rings 218, 219. The stabilizing ring 216 and the tapes 218, 219 have the same shape as the rim 222. When the device is constructed, the first tape 218 is located between the rim 222 and the membrane 210. The second tape 219 is located between the membrane 210 and the stabilizing ring 216. The stabilizing ring 216 holds the membrane 210 in place during the formation of the corrugations 212 during the production process.

[0119] exist Fig.17b In the embodiment of the device shown, the body 202 includes three inclined cam surfaces 220 located on the uppermost surface of the body 202 . Fig.19 An isometric view of the underside of the handle member 204 and the piston 206 is shown in isolation. In this isolated view, it can be seen that the underside of each spoke 226 of the handle member 204 includes a ridge 228 on its underside. Fig.16a and 16b As seen in FIG. 2 , each of the ridges 228 contacts a corresponding inclined cam surface 220 of the body 202 of the device 201 .

[0120] Now refer to Figures 20 to 25 Describe the operation of the device. Figures 8a to 8b 16 to 25 are illustrations showing how the position of the piston 8 in the cavity 6 can be used to adjust the channel 4, which also applies to the third embodiment of the invention shown in FIGS. 16 to 25.

[0121] Figures 20 to 22 are diagrams demonstrating how the position of piston 206 may be used to adjust the tension of membrane 210. For clarity, these diagrams show cross-sections of handle member 204, piston 206, and membrane 210 separated from the other components of device 201.

[0122] Figures 23 to 25 2 is a diagram showing how the position of piston 206 can also be used to adjust the size of passage 224. Figures 20 to 25 In the illustrated embodiment, the piston 206 adjusts both the size of the channel 224 and the tension of the membrane 210 .

[0123] When the handle member is in Fig. 20 and 23 In the first position shown, each ridge 228 contacts the corresponding inclined cam surface 220 at its highest point. As a result, the piston 206 is not in contact with the membrane 210. In this position, the force applied by the piston 206 to the membrane 210 is zero. Therefore, the tension in the membrane 210 is the base tension (i.e., the minimum tension in the membrane). This base tension is provided by attaching the membrane 210 to the edge 222 of the body 202. The compressible portion 208 is in a compressed state, which biases the movement of the piston 206 axially downward toward the membrane 10.

[0124] like Fig.23 As shown, when the handle member 204 is in the first position, a channel 224 is formed between the wall of the cavity formed by the body 202 of the device 201 and the piston 206. The arrows show how sound propagates along a sound path 252 containing the channel 224 through the device.

[0125] The user can then rotate the handle member 204 to a second position, such as Fig.21 and 24 As shown. In the second position of the handle member 204, each ridge 228 contacts the corresponding inclined cam surface 220 at the midpoint of the inclined cam surface 220. When the handle member is rotated from the first position to the second position, each ridge moves downward along the corresponding inclined cam surface 220. The entire handle member 204 moves axially downward toward the body 202 of the device 201, and thus the piston 206 moves axially downward toward the membrane 210. The inclined cam surfaces 220 and the ridges 228 on the spokes 226 together convert the rotational movement of the handle member 204 into axial movement of the piston 206.

[0126] exist Fig.21In the second position shown, the piston 206 is in a position where the piston 206 just contacts the surface of the membrane 210. In the absence of the corrugations, when the piston 206 contacts the membrane 210, the primary vibration mode of the membrane 210 is disabled, and the center of the membrane 210 can be considered to remain stationary. Therefore, only the higher harmonic vibration modes of the membrane 210 are enabled, resulting in a sudden increase in attenuation. The inclusion of the corrugations 212 in the membrane reduces this effect. Therefore, when the piston just contacts such a membrane 210 containing the corrugations 212, the attenuation level increases more smoothly.

[0127] Because the piston 206 includes the compressible portion 208, some of the force that would otherwise be applied to the membrane 210 (e.g., compared to a rigid piston without a compressible portion) is used to compress the compressible portion 208. This results in less force being applied by the piston 206 to the membrane 210, and therefore less increase in tension in the membrane 210. Thus, as the piston 206 moves to just contact the surface of the membrane 210 (compared to a rigid member), the attenuation level increases more gradually.

[0128] In such Fig.24 In the second position shown, the piston 206 is positioned to reduce the size (e.g., width and / or length) of the channel 224 compared to the first position. As previously described, reducing the width of the channel 224 increases the effective acoustic mass and acoustic losses of the channel 224. Reducing the length of the channel 224 reduces the effective acoustic mass and acoustic losses of the channel 224. This, together with the changed tension of the membrane 210, changes the overall response of the device 201.

[0129] The user can further rotate the handle member 204 to a third position, such as Fig. 22 and 25 In the third position of the handle member 204, each ridge 228 contacts the corresponding inclined cam surface 220 at the lowest point. This corresponds to a limit of rotational movement of the handle member 204 (in this direction), and therefore corresponds to a limit of axial movement of the piston (towards the membrane).

[0130] exist Fig. 22 In the third position shown, the piston is in contact with the surface of the membrane and exerts a greater (e.g., maximum) force on the membrane (e.g., greater than the force exerted when the handle member 204 is in the second position and the piston 206 just contacts the surface of the membrane 210). The force exerted by the piston 206 also causes a more significant deformation of the rest of the membrane 210. Fig. 22 As shown, in this position, the membrane 210 is deformed from a substantially flat surface to a concave or frustoconical shape due to the force exerted by the piston 206 on the membrane 210. In this configuration, the tension of the membrane 210 is further increased above the base tension (e.g., the tension is increased to its maximum value). This results in a greater damping provided by the device 201 (i.e., greater than when the handle members are in the Fig. 20 and 21 attenuation provided by device 201 when in the first position or the second position shown).

[0131] exist Fig.25 In the third position shown, the piston 206 contacts the wall of the cavity in the body 202 of the device 201. Thus, there is a minimum channel width (e.g., no channel) between the wall of the cavity of the body and the piston 206. In this arrangement, the minimum channel width together with the high tension of the membrane causes the device to provide its maximum attenuation. The compressible member 214 is in its minimum compression state.

[0132] In embodiments where the attenuation provided by the device is minimal, when the handle member is in the first position, the channel 224 can be described as 'open' and the device 201 can be described as being in an 'open' configuration. In embodiments where the attenuation provided by the device is maximal, when the handle member is in the third position, the channel 224 can be described as 'closed' and the device 201 can be described as being in a 'closed' configuration.

[0133] Of course, as will be appreciated by those skilled in the art, the handle member 204 may be moved to Figures 20 to 22 and any intermediate position between the first position, the second position and the third position shown in 23 to 25 so as to achieve the desired acoustic response of the sound path 252.

[0134] Figures 26a to 26b A cross-sectional view of a device according to a fourth embodiment of the invention is shown, the device comprising a body 302 formed by an upper portion 302a and a lower portion 302b. The device further comprises a membrane (not shown) and a cover 308, wherein the cover 306 is arranged to provide additional attenuation. For example, when the user is in an environment with a high sound pressure level, the cover 306 can be used to minimize the sound entering the device. Fig.26a In , the cover is shown in an open configuration, wherein a sound path (not shown) is open to allow sound to enter the device. Figure 26b , the lid is shown in a closed configuration, wherein a sound path (not shown) is open to allow sound to pass through the device. A hinge may be used to allow the lid to be moved manually or automatically from an open position to a closed position (and vice versa).

[0135] Fig. 27 A graph comparing the frequency response of an embodiment of the present invention with the frequency responses of three prior art passive earplugs is shown. The graph shows the relationship between frequency on the horizontal axis and attenuation on the vertical axis. Both axes have a logarithmic scale. The attenuation shown is relative to the natural, unobstructed frequency response of the human ear system. Therefore, it takes into account the well-known typical sensitivity variation of humans that depends on frequency.

[0136] The top, substantially horizontal curve 170a corresponds to an embodiment of the present invention, similar to the embodiment described above where the piston is almost fully open. It can be seen that the attenuation provided is substantially constant over the entire frequency spectrum. This means that the user will experience sound. Similarly, curve 170b shows the situation when the piston is half closed. Here, a greater attenuation is provided, but it is still substantially constant with frequency. The bottom curve shows the response when the piston is almost closed. Here, the attenuation is at a maximum (approximately 25dB), but remains substantially constant with frequency.

[0137] By contrast, curves 172, 174 and 176 show the corresponding frequency responses of typical passive earplugs, which are inserted into the user's ear canal to varying degrees. The top curve 172 shows that the earplug is inserted the least (significantly less than it would be expected). This means that there is almost no attenuation at low frequencies (which can be dangerous). The other curves 174, 176 show that the earplug is more fully inserted and therefore more effective. However, it can be seen that in all three cases, the attenuation increases significantly with frequency, which means that higher frequency sounds are filtered out disproportionately compared to lower frequencies. As a result of this, the sound experienced by the user is blurred, which can lead to problems with speech intelligibility when listening to a colleague, for example. This may prompt the user to remove the earplug or insert it improperly, making the earplug less effective than expected.

Claims

1. A device for insertion into the ear canal of a mammalian subject, comprising: a body having at least one sound path extending therethrough; a first adjustable acoustic-mechanical portion comprising an adjustable channel forming at least a portion of the sound path; a second adjustable acoustic-mechanical portion, the second adjustable acoustic-mechanical portion being arranged acoustically in series with the first adjustable acoustic-mechanical portion, the second adjustable acoustic-mechanical portion comprising an adjustable membrane; as well as an adjustment device for simultaneously adjusting the first adjustable acoustic-mechanical portion and the second adjustable acoustic-mechanical portion to change the acoustic response of the at least one sound path; wherein the adjustable passage is defined by the space between the wall of a cavity within the body and a piston arranged in the cavity, the cavity and the piston each having a frustoconical shape, so that the adjustable passage has the form of a frustoconical shell, and wherein adjustment of the passage is achieved by moving the piston relative to the cavity.

2. A device for insertion into the ear canal of a mammalian subject according to claim 1, wherein the adjustment device includes a common actuator, which is arranged to simultaneously adjust both the first adjustable acoustic-mechanical part and the second adjustable acoustic-mechanical part.

3. A device for insertion into the ear canal of a mammalian subject according to claim 2, wherein the actuator comprises a user operable member arranged to operate at least a portion of the adjustment device.

4. A device for insertion into the ear canal of a mammalian subject according to claim 1, 2 or 3, wherein the adjustment device is configured to adjust the length of the adjustable channel.

5. A device for insertion into the ear canal of a mammalian subject according to claim 1, 2 or 3, wherein the adjustment device is configured to adjust the width of the adjustable channel.

6. A device for insertion into the ear canal of a mammalian subject according to claim 1, wherein the piston is arranged to move axially within the cavity, and the device for insertion into the ear canal of a mammalian subject includes at least one elastic member, which is arranged to bias the piston out of the cavity, and wherein the adjustment device includes an actuating member, which is arranged to drive the piston axially into the cavity against the elastic bias.

7. A device for insertion into the ear canal of a mammalian subject according to claim 6, wherein the actuating member is arranged to rotate relative to the piston, and the device for insertion into the ear canal of a mammalian subject further includes a device for converting the rotational movement of the actuating member into axial movement of the piston.

8. A device for insertion into the ear canal of a mammalian subject according to claim 6 or 7, wherein the piston is arranged such that movement of the piston adjusts the tension of the membrane.

9. A device for insertion into the ear canal of a mammalian subject according to claim 8, wherein the piston is coupled to a resilient member arranged to act on the membrane or a portion of the body to which the membrane is attached.

10. The device for insertion into the ear canal of a mammalian subject according to claim 8, wherein the piston is arranged to contact the membrane.

11. A device for insertion into the ear canal of a mammalian subject according to claim 10, wherein the piston includes a compressible portion.

12. A device for insertion into the ear canal of a mammalian subject according to claim 11, wherein the compressible portion of the piston contacts a surface of the membrane.

13. The device for insertion into the ear canal of a mammalian subject according to claim 10, wherein the piston has a position that does not contact the membrane and does not change the tension of the membrane from a base value.

14. A device for insertion into the ear canal of a mammalian subject according to claim 10, wherein the piston has a plurality of positions of contact with the membrane, the plurality of positions corresponding to a plurality of magnitudes of force applied to the membrane and a plurality of tensions in the membrane.

15. A device for insertion into the ear canal of a mammalian subject according to claim 1, 2 or 3, wherein the passageway comprises an adjustable barrier member.

16. A device for insertion into the ear canal of a mammalian subject according to claim 1, 2 or 3, wherein the membrane is a separate component attached to the body, and the body defines a circumferential edge to which the membrane is attached.

17. A device for insertion into the ear canal of a mammalian subject according to claim 1, 2 or 3, wherein the membrane comprises at least one corrugation.

18. A device for insertion into the ear canal of a mammalian subject according to claim 17, wherein the corrugations are circular and centered at the geometric center of the membrane.

19. The device for insertion into the ear canal of a mammalian subject according to claim 17, wherein the membrane comprises a plurality of corrugations.

20. A device for insertion into an ear canal of a mammalian subject according to claim 1, 2 or 3, further comprising a controller arranged to control the adjustment device so as to change the acoustic response of the at least one sound path.

21. A device for insertion into the ear canal of a mammalian subject according to claim 1, 2 or 3, further comprising a user input arranged to enable the user to control the operation of the device for insertion into the ear canal of a mammalian subject.

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