WO2015024077A1

WO2015024077A1 - Hearing aid device

Info

Publication number: WO2015024077A1
Application number: PCT/AU2014/050197
Authority: WO
Inventors: Andy Zhang; Rodney MILLARD; Robert Cowan; James Patrick
Original assignee: Hear Ip Pty Ltd
Priority date: 2013-08-23
Filing date: 2014-08-25
Publication date: 2015-02-26

Abstract

The present invention provides a hearing aid device comprising: a housing, an input audio transducer disposed within the housing, an aperture extending through the housing wall allowing for a sound wave to pass from the housing exterior to the microphone, a substantially gas-impermeable diaphragm disposed to cover the aperture, a chamber disposed between the microphone and the diaphragm, wherein the diaphragm, chamber and microphone form a substantially gas-tight enclosure. The present hearing aid may be configured as a behind-the-ear device, and may be an external component of a cochlear implant hearing aid device.

Description

HEARING AID DEVICE

FILED OF THE INVENTION

The present invention relates generally to housings for hearing aids. More particularly, the housings are applicable (although not exclusively) to behind-t he-ear type hearing aids often used in the context of cochlear implant hearing aid systems.

BACKGROUND TO THE INVENTION

Hearing aid devices are used to supply the hearing-impaired with amplified ambient signals to compensate for the individual's impairment. These devices generally include one or more audio input converters, a signal processing facility with amplification and an output audio converter. The input audio transducer is generally a microphone, or an electromagnetic receiver such as an induction coil. The output audio converter may be implemented as an electroacoustic converter, e.g. miniature loudspeaker, or as an electromechanical converter, such as a bone conduction output means, The output eonverter may generate audio output signals, which are routed to the ear of the patient and generate an audio perception in the patient. The output converter may in some cases be a neural stimulatory device (such as an implantable cochlear electrode). The amplifier is generally integrated into a signal processing facility which may filter or augment certain frequencies. The power supply to the hearing aid device is typically b means of a battery arranged in the hearing device housing. The essential electronic components of a hearing device are generally arranged on a printed circuit board,

Hearing aid devices are known in various housing configurations. With ITE (In-The-Ear) devices a housing containing all functional components, is for the most part worn within the auditor canal. CIC (Completely-ln-Cana!) hearing aid devices are similar to the ITE hearin devices, but are however disposed completely within the auditory canal. With BTE hearing devices, (Behind-The-Ea r) a housing with components such as a battery and signal processing facility is worn behind the ear and a flexible acoustic tube guides the acoustic output signals from the housing to the auditory canal, or to a cochlear electrode device. IC-BTE hearing devices (Receiver-ln-Canal Behind-The-Ear) equate to the BTE hearing devices, but the receiver is worn in the auditory canal. Ideally hearing aid device audio input converters are in open communication with the user's environment, this providing sound of greatest fidelity to the user. However, it is accepted in the art that a covering of some type over the microphone is required given the propensity for dirt, dust, perspiration, oil, hair and other contaminants to lodge about the microphone.

A further problem is that of wind passing over the aperturefs) leading in some circumstances to the generation of interfering sound waves. One significant reason for the occurrence of interference or wind noise if wind blows over the surface of a hearing device over a critical speed laminar flow about the apertures changes into a turbulent flow. If this turbulence occurs in the region of the microphones and/or the microphone aperture of a hearing aid device housing, noise is produced. Such interference can seriously undermine the fidelity of sound provided by a hearing aid device in windy weather. The prior art provides a range of covers, that inhibit the lodgement of debris about the microphone and/or ameliorate the problem of wind-induced noise. While some are effective, the covers that are more acoustically transparent tend to trap or admit contaminants, or are not efficient at lessening wind noise. Those that operate more effectively tend to be less acoustically transparent, and therefore have problems in attenuating or otherwise negatively affecting sound reproduction.

An example of the prior art is the Freedom BTE processor {Cochlear Ltd) which employs a moisture resistant cover to protect the microphone ports from being directly exposed to the environment. The cover is a plastic portion, which may be snapped on and off the BTE case over the microphone ports in the BTE case. There are three open holes in the cover, which are aligned with the microphone ports. These open holes are covered with a Gore-Tex diaphragm on the inner surface of the cover to prevent moisture and dust from entering the microphone ports. However, the Gore-Tex cover has to be replaced at regular intervals due to fouling by contaminants to ensure its effectiveness. This is expensive and inconvenient to the user, More importantly, dust and oil can still accumulate in the openings of the cover and cause gradual deterioration of the performance without being noticed by the user. Some hearing aids of the prior art attempt to overcome problems presented by the use of porous membranous microphone covers by the use of more solid covers. However, such covers act to attenuate, induce unwanted resonances or otherwise modify the characteristics of the sound entering the microphone. This modification of sound can adversely affect the sound quality experienced by the user.

Further problems of moisture ingress are also seen given the porous nature of these covers. This may limit the ability of an individual to freely use the hearing aid while swimming, bathing or in environments of high humidity.

It is an aspect of the present invention to overcome a problem of the prior art by providing hearing aid device that is low in maintenance yet able to transmit sound to the user which is not materially diminished in quality, while also providing a barrier to moisture. It is a further aspect to provide an alternative to hearing aid devices of the prior art.

The discussion of documents, acts, materials, devices, articles and the fike is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge i the field relevant to the present invention as it existed before the priority date of each claim of this application.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a hearing aid device comprising: a housing, an input audio transducer disposed within the housing, an aperture extending through the housing wall allowing for a sound wave to pass from the housing exterior to the microphone,, a substantially gas-impermeable diaphragm disposed to cover the aperture, a chamber disposed between the microphone and the diaphragm, wherein the diaphragm, chamber and microphone form a substantially gas-tight enclosure. In one embodiment the diaphragm has an area equal to or less than about 20 mm². The diaphragm may be substantially circular, optionally of diameter about 3mm to about 5 mm. in one embodiment the chamber is substantially circular, optionally having a diameter of between about 2.7 mm to about 3.3 mm. The chamber may have a depth as measured from the inner surface of the diaphragm to the chamber floor of between about 100 μηη to about 200 μιηη.

In one embodiment, the chamber floor comprises a aperture configured to convey sound waves from the chamber to the microphone.

In one embodiment the diaphragm is retained by a force or pressure exerted on the diaphragm. The force or pressure may be applied at one or more points distal to the edge of the aperture to provide an area of diaphragm that is supported by an underlying structure, but is free to vibrate. The supported area of diaphragm may extend between about 1 mm to about 2 mm from the point of application of force or pressure toward the centre of the diaphragm. In one embodiment the area of diaphragm that is supported by the housing, but is free to vibrate extends at most about 1 mm or about 2 mm beyond the edge of the aperture.

The diaphragm may have a thickness of between aboutSO μηι to about 160 μηι, and may have at least 1, 2 or 3 layers, or at most 1, 2 or 3 layers. The diaphragm consists of or comprises a poiymeric material, which in one embodiment is a polyester material such as a polythylene terephthalate or derivative thereof. The polymeric material has been modified to increase tensile strength. The modification may comprise stretching. In one embodiment the polythylene terephthalate is a biaxialy-oriented polyethylene terephthalate.

The hearing aid device may be configured as a behind-the-ear hearing aid device, and in one embodiment is configured as an external component of a cochlear implant hearing aid device. DETAILED DESCRIPTION OF THE INVENTION

After considering this description it will be apparent to one skilled in the art how the invention is implemented in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example on y, and not limitation. As such, this description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention. Furthermore, statements of advantages or other aspects apply to specific exemplary embodiments, and not necessarily to all embodiments covered by the claims.

Throughout the description and the claims of this specification the word "comprise" and variations of the word, such as "comprising" and "comprises" is not intended to exclude other additives, components, integers or steps.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may.

The present invention is predicated at least in part of applicants finding that the use of a gas tight chamber having a diaphragmatic covering through which ambient sound waves are transmitted are capable of excluding contaminants from a hearing aid while still providing acceptable sound transmission performance. Accordingly, in a first aspect the present invention provides a hearing aid device comprising: a housing, an input audio transducer disposed within the housing, an aperture extending through the housing wall allowing for a sound wave to pass from the housing exterior to the microphone, a substantially gas- impermeable diaphragm disposed to cover the aperture, a chamber disposed between the microphone and the diaphragm, wherein the diaphragm, chamber and microphone form a substantially gas-tight enclosure.

The Examples herein demonstrate empirically a sealed enclosure capable of excluding contaminants, whereby negative acoustic characteristics such as attenuation and unwanted resonances are limited. A basic embodiment {not drawn to scale) is shown in Fig. 1, having a housing wall 2, the housing wall 2 having an aperture 3 upon which a diaphragm 4 is disposed. A base portion 6 forms the floor of the chamber 8. The base portion 6 includes an aperture 10 through which rubber tubing 12 passes, the rubber tubing 12 being continuous with a rubber boot 14 within which a microphone 16 is disposed. It will be noted that a sealed volume of air is formed between the diaphragm 4 and microphone 16. Vibration of the diaphragm 4 by ambient sound waves propagates the sound waves through the sealed volume of air, which in turn vibrates the diaphragm of the microphone, importantly, the diaphragm 4 completely excludes any environmental contaminants from the microphone, thereby obviating the need for cleaning and other maintenance.

As used herein, the term "hearing aid device" is not intended to be construed narrowly to include each and every component necessary to form a fully operable hearing aid such as a signal processing circuit, a loudspeaker, an amplifying circuit, a volume control circuit, a battery chamber, a battery, cochlear electrodes array and the like. As will be apparent, the present invention may be embodied in only a part, component or module of a hearing aid.

As used herein, the term "housing" is intended to include a portion of the entirety of a hearing aid housing, as well as a complete housing. Modem hearing aids typically have housings formed of light weight plastics which are fabricated in parts and assembled to form a complete housing structure. Ail parts of a housing are not necessarily purely exterior- facing, and may include invaginations, depressions, channels, ports and the like The input audio transducer may be any type of device capable of converting sound wave to an electrical signal suitable for use in a hearing aid device. Typically, the transduce is a microphone selected from the following types: unidirectional, omni-directional, combined uni-omni-directional. It is to be understood that the hearing aid device may comprise more than one microphone, Typically, each microphone is associated with a separate aperture in the housing. The aperture may be any interruption in the wall of the housing capable of admitting a sound wave, including a simple hole extending directly through the wall. Also contemplated are more complex arrangements such as gratings, convoluted passages, partially covered apertures and the like. The aperture is typically uncovered, but may be covered by (or have disposed within) a material which is incapable of excluding contaminants to the desired level.

The aperture may be any shape but is typically circular or ovoid. As used herein, the term "substantially gas-impermeable" is intended to mean that the diaphragm is substantially incapable allowing the passage of a gas under conditions of normal hearing aid use, and/or over a reasonable period of time. As will be apparent to the skilled artisan, it is possible to expose a diaphragmatic material to extreme conditions of gas pressure, and where necessary for extended periods of time in order to achieve the transmission of gas across a diaphragm. Furthermore, the diaphragm may be twisted or heated in order to compromise gas-impermeability. These more extreme circumstances will not be encountered during normal hearing aid use and should not be used to assist in the interpretation of the term "substantially gas-impermeable" in the characterization of materials for use in the diaphragms forming part of the present invention.

Furthermore, i the context of the present invention, the diaphragm need not be absolutely gas-impermeable under conditions of normal hearing aid use. The diaphragm may only be gas-impermeable to the extent that the gas contained in the chamber is not forced out of the chamber due to any compression caused by a soundwave, but is instead contained therein. As will be appreciated by the skilled person, a sound wave only applies a pressure to the diaphragm for an instant and therefore so long as the diaphragm i capable of resisting transmission of gas for that short period it will be useful in the context of the present invention. The diaphragm ma cover the aperture by being disposed on the outside of the housing wall, or the inside. Alternatively it may be disposed with the aperture. For example, the housing may consist of two layers, the aperture extending through the two layers, and the diaphragm disposed between the two layers. In some forms of the invention, the diaphragm is anchored to the housing wall but in others it is anchored to another structure internal to the hearing aid such as a microphone housing. The chamber of the hearing aid device may be of any suitable geometry or volume. Typically the chamber is symmetrical along the longitudinal and lateral a¾e≤, and has a fixed cross-sectional area from the ceiling to the floor. Other arrangements are contemplated, the general aim being to maintain fidelity of the sound waves transmitted through the chamber to the input signal transducer.

The chamber is disposed between the diaphragm and microphone such that a sound wave impinging on the diaphragm is transmitted from the diaphragm to the input signal transducer via the fixed volume of gas in the chamber, it is not necessary that the diaphragm, chamber and input signal transducer are aligned along an axis, however this will be a typical arrangement in a hearing aid.

The diaphragm, chamber and m icrophone form a substantially gas-tight enclosure. The preferred hermetically sealed nature of the enclosure may be achieved by any suitable method such as by the use of sealants., flexible boots, frictionai engagement between parts, glues and the like. It will be understood that the enclosure only need by gas-tight under ordinary operating conditions of a hearing aid.

Pressure of the gas inside the chamber is typically substantially equivalent to that within the enclosure, which is in turn typically substantially equivalent to atmospheric pressure.

In one embodiment, the diaphragm has an area of between about 7 mm² and about 20 mrr^; or where the diaphragm is circular a diameter of between about 3 mm to about 5 mm. These areas and diameters refer to the surface of the diaphragm as it is presented to the exterior of the hea ring aid and capable of transmitting a sound wave to the gas within the chamber. Reference is made to Fig. 2, where the diameter of the diaphragm is marked as "d". As described in more detail infra, some embodiments of the hearing aid device provide for a larger area of diaphragm being exposed to the outside, with a smaller subset of that area being free to vibrate in response to the impingement of a sound wave. In that case, the prescribed areas and diameters refer to the smaller subset area.

In one embodiment the chamber is substantially circular, optionally having a diameter of between about 3.0 mm to about 5.0 mm, optionally between about 2.7 mm to about 3.3 mm. Where the chamber is not circular, the chamber may have dimensions providing an equivalent cross-section area to the aforementioned circular forms of the chamber

The chamber may be any depth found to suitable in the context of the present inventions, however the accompanying Examples demonstrate that embodiments having a depth of between about 100 μιη to about 200 μτη are particularly advantageous.

The various diameters and depths of the chamber described herein may be interpreted as defining certain ratios of diameter to depth useful in identifying dimensions of advantageous forms of the invention. Chambers having ratios so-defined may provide advantageous forms of the invention.

The chamber floor may simply be formed by a face of the input audio transducer. More typically, the floor is a separate dedicated structure of planar geometry. In that case, an aperture is generally present in the floor, to allow sound waves to pass out of the chamber and to the input audio transducer. Accordingly, in one embodiment the chamber floor comprises an aperture configured to convey sound waves from the chamber to the microphone. Construction of the term "aperture" in the context of the chamber flaw is guided by the same or similar considerations as put forward supra in relation to the a erture in the housing wall.

The diaphragm is retained on o about the aperture i a manner allowing for the efficient transmission of sound waves through to the gas in the underlying chamber. As will be understood the edge of the diaphragm should be firmly retained to prevent any dissipation of the sound energy to a free end of the diaphragm. Furthermore, the diaphragm should not be retained loosely, with there being any significant free play available to dissipate sound energy. Indeed, in some embodiments the diaphragm is placed under at feast a minimal amount of tension to facilitate the efficient transmission of sound.

To that end, in one embodiment the diaphragm is retained under a force or pressure 5 exerted on the diaphragm. The force or pressure is typically applied about the complete circumference of the diaphragm. As shown in the accompanying Examples, sound attenuation can be improved by the use of a clamping force. The force or pressure may be applied by any suitable method including the use of clamps, screws, application of a plate urged toward the diaphragm, or by stretchin the diaphragm over a ridge or edge.0 Preferably a clamping force is applied to the perimeter of the membrane.

In some embodiments, where the diaphragm is retained by a force or pressure exerted on the diaphragm, at least part of the diaphragm may be supported by an underlying structure, such as the housing. Accordingly, one embodiment of the invention provides that the force5 or pressure is applied at one or more points distai to the edge of the aperture to provide an area of diaphragm that is supported by an underlying structure, but is free to vibrate.

In one embodiment, the supported area of diaphragm extends between about 1 mm to about 2 mm from the point of application of force or pressure toward the centre of the0 diaphragm.

The diaphragm may be fabricated from any suitable material{s) known to the skilled artisan. In one embodiment, the diaphragm is fabricated from a polymeric material such as a plastic including a polyester, polyethylene terephthalate, polyethylene, high-density polyethylene,5 low-density polyethylene, polyvinyl chloride, polyvinylidene chloride, polypropylene, polystyrene, high impact polystyrene, polyamides, acrylonitriie butadiene styrene, polyethylene/acrylonitrile butadiene styrene, polycarbonate, polycarbonate/acrylonitrile butadiene styrene, polyu ethanes, meiamine formaldehyde, phenolics, polyetheretherketone, polyetherirnide, poly lactic acid, and polymethyS methacrylate.

D The accompanying Examples demonstrate advantages in polyesters such as polythylene terephthalate materials, particularly where the material has been modified to increase tensile strength (such as in "BoPet" materials). The present invention will find utility in any type of hearing aid (many of which are described if the Background Section herein). A particular application is in the BTE sound processor components of cochlear implant hearing aid systems. The present invention will now be more fully described by reference to the following non-limiting examples. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram (not drawn to scale) of a portion of a hearing aid device of the present invention.

F!G. 2 is a diagram of a test jig for the evaluation of diaphragm and device geometries.

FIG. 3 is a diagram of an acoustic testing and measurement system.

FIG. 4 is a graph showing attenuation as a function of frequency for a PET diaphragm (thickness 100 pm) having a diameter of 5mm (lower Sine) or 8mm (upper line).

FIG. 5 is a diagram of a modified test jig for the evaluation of diaphragm and device geometries,

FIG. 6A is a graph showing attenuation as a function of frequency for a 50 pm thickness polyimide diaphragm of diameter 5mm, the depth of the chamber underlying the diaphragm being 125 pm (50), 100 pm (52), or 50 pm (54). The line (56) is a control whereby no diaphragm was used,

FIG. 6B is a graph showing attenuation as a function of frequency for a 75 pm thickness polyimide diaphragm of diameter 5mm, the depth of the chamber underlying the diaphragm being 125 pm (50), 100 pm (52), 50 μιτι (54). The line (56) is a control whereby no diaphragm was used. FIG. 6C is a graph showing attenuation as a function of frequency for a 50 μηι thickness PET diaphragm of diameter 5mm, the depth of the chambe underlying the diaphragm being SO μιπ (50), 100 μηι (52), 125 μηι (54), The line (56) is a control whereby no diaphragm was used.

FIG. 6D is a graph showing attenuation as a function of frequency for a 50 μιη thickness PET diaphragm of diameter 5mm, the depth of the chamber underlying the diaphragm being 50 μίη (54), 100 μπι (52), 150 μιτι (50). The line (56) is a control whereby no diaphragm was used.

FIG. 7 is a graph showing attenuation as a function of frequency for a PET diaphragm of diameter 5mm, the depth of the chamber underlying the diaphragm being 50 \x . The thickness of the diaphragm was 50 μιη (60), 50 μητι clamped hard (62), 75 μηη (64), 75 μηι clamped hard (66). The line (68) is a control whereby no diaphragm was used

EXAMPLE 1: Assessment o diaphragm materials and component geometries.

The aim of this Example was to investigate the relationship between the microphone performance and parameters such as the chamber depth, and diaphragm thickness and diameter. An arrangement using an omni-microphone with a single sealed port was used. Performance measurements included sensitivity, frequency response and noise floor, in addition, vibration sensitivity was investigated and characterised, since a sealed microphone port could cause a significant increase in vibration sensitivity.

Materials and Method

A mechanical test jig was constructed to allo for the easy variation of diaphragm materials and the dimensions such as thickness f and diameter d, as well as chamber depth h, Fig. 2 shows the schematic drawing of the test jig having a metal enclosure 2 having an aperture 4 equipped with a collar 6 into which a Knowies microphone 8 is sealingly engaged. Disposed above the aperture was a spacer plate 10 having a circular cut-out of certain diameter (edge of the cut-out shown at 12) positioned about the aperture 4. The diaphragm 14 was layered over the spacer plate 10. Top plate 16 was layered over the diaphragm 14 to form a sandwich arrangement. A chamber 18 was formed by the diaphragm 14, the upper wall of the metal box 2 and the edge of the spacer plate 12. This arrangement provides for different diaphragms and spacers to be tested in a variety of combinations of thickness and height, respectively. The design of the test jig closely resembles the proposed diaphragm-on-chamber structure of the seafable microphone. It will be noted that the diaphragm thickness f, diaphragm material, and the chamber depth h may be varied by dissembling and reassembling the test jig.

Acoustic testing and measurement were carried out in a sound booth as shown in Fig.3, which consists of a B&K 4232 Anechoic Test Box 2, into which is placed the test jig of Fig. 2 with microphone 4, a speaker 6 disposed over the diaphragm of the test jig 4, a reference B&K ½"^' microphone 8 with B&K 2260 Sound Analyser 10, reference EM microphone 12, the speaker 6 connected to Philips FA443 Stereo Power Amplifier 14. Analyses was performed using a Stanford Research Systems SR785 Dynamic Signal Analyser 16, connected to the power amplifier 14, the reference EM microphone 12, and the test jig microphone 4.

The SR785 Dynamic Signal Analyser is a tool for spectrum analysis of acoustic signals. Periodic chirp noise was used as the sound source for calibration, and the microphone output was measured in dBV rms from 100 Hz to 10 kHz.

The B&K 2260 sound analyser was used to measure the sound pressure level inside the test box. The frequency response of the B&K anechoic box was calibrated first and taken into account in microphone calibration to ensure a flat sound field with sound pressure equal in all frequency bins.

Experimental Results

The test diaphragm material was ΙΟΟμηη thick PET film (overhead projector transparency film), Two different spacer plate cut-out diameters of the 5mm and 8mm were tested with a δθθμηι thick spacer to create the air chamber. Fig. 4 shows the attenuation of the two cutout diameters from 100 Hz to 10 kHz. The attenuation for the 8mm diameter is less than 5 dB and about 1 dB above 1 kHz. It will be noted that the resonance of the diaphragm-on- chamber structure was measured to be around 5 kHz. This is a key performance difference from that of microphones of the prior art that use metallic diaphragms (such as titanium). EXAMPLE 2 _mm Assess^

test jig.

A diaphragm diameter of Smm was set as the upper limit in these studies. The chamber diameter was set at Smm to facilitate integration in BTE processors for cochlear implants. Materials and Method

Fig. 5A shows the modified test jig. The microphone 2 was placed in the test-jig with its sound in-let 4 connected to an air-filled chamber 6, which was sealed under a diaphragm 8 by a top clamping piate 10 fastened with screws 12, Different to the jig set-up of Example 1, this jig (seen in plan view at Fig. 5B) created an offset between the clamped edge 14 of the diaphragm and th rim of the air filled cham ber 16. The diaphragm was 5 mm in diameter and the air cham ber Smm in diameter. This arrangement creates a 1 mm area 18 of the diaphragm which is supported from the underside but not clamped from the edge of the chamber. The benefits of this arrangement are at least twofold. Firstly, the mechanical rigidity of the diaphragm is increased to be robust enough to withstand handling, which in turn allows the use of a thinner diaphragm. Secondly_,, the active region over the air chamber is increased due to the undamped edge of the diaphragm, which in turn allows fo a smaller chamber diameter.

Experimental Results

Tabie 1 shows the results of testing various materials (including single iayer and mutti laye laminates), it will be noted that the multilayer laminates of thickness less than 100pm introduce more attenuation than some of the single layered films. More importantly, the multilayer laminates are easily wrinkled, which is not desirable as the sealable diaphragm. The single layered films with thickness of less than 50μηα were measured to have less than 5 dB loss. The results indicate that the 50μηι thick poiyimide film is a useful compromise between acoustic performa nce and mechanical rigidity. Table 1. Testing of diaphragm materials using a 3mm diameter

chamber and 5mm diameter clamping top-p!ate.

Fig. 6 shows the measured frequency response of attenuation for the diaphragm made of polyimide {Pi), polyethylene pofyterephthaiate (PET) and metalized PET (MPET). Each different line as marked is of the measurement with either (i) an open microphone port (no diaphragm), or (ii) the microphone port covered with a diaphragm, and the spacer plate thicknesses of 50, 100 and 150 μιτ! (which is also the depth of the air chamber).

These results indicate that useful microphone performance was achieved with the use of a 50 - 75 μιη thick polyimide or polyester film with a clamped diameter of 5 mm; and an air chamber 3 mm in diameter and 50 - 100 μηι in depth.

It will be noted that attenuation level is affected by the clamping force applied on the edge of the diaphragm. As shown in Fig. 7, the hard clamping further reduces the attenuation across frequency range up to the resonance at 6 kHz in comparison with the loose clamping conditions.

An appropriate clamping force may be chosen by routine experimentation on the part of the skilled artisan. Trials may be conducted whereby the effect on any variable (such as frequency response or sensitivity of the microphone) is assessed as a function of clamping, force. In this way, an appropriate clampin force (or a range of appropriate clamping forces) may be identified.

The results in this Example demonstrate a sealabfe microphone with minimal losses of sensitivity {1-5 dB) and almost no change in frequency response below 6 kHz. In addition, tough and biocompatible polymer diaphragms {50 -75 ϊη polyimide film) can be used as the waterproof element to protect the microphone port in a hearing aid device housing. The required diameter of the waterproof diaphragm is 5mm and the air chamber has a depth of 50 (τι and a diameter of only 3 mm. Such a combination of material and structure enables the scalable microphone design to b robust enough to withstand the normal handling of the outer surface of a hearing aid device housing.

Arrangements shown herein are also able to meet or exceed in Ingress Protection (IP) Rating The microphone ports should be sealed to an !P rating equivalent or better than 57. The polyimide diaphragm and method of construction provide an ip rating of 68.

18 Furthermore, the Measured Omni Microphone Performance should show a minimum input dynamic range of 25 dB, up to 65 dB, equivalent input noise floor of 25 dB SPL, and resonant frequency above 5 kHz. These results demonstrate a sealabie microphone design with less than 5 dB loss of sensitivity in comparison with that of a Knowles microphone in a frequency bandwidth from 100 Hz to 6 kHz.

Additionally, diameter of diaphragm should be less than or equal to 5 mm, and no necessity to increase the overall volume of the microphone inside the housing. Scalable microphone structures described herein have an outer diameter of 5 mm and the air filled chamber, where the diaphragm is suspended, is only 3mm in diameter and 50 μηι in depth. The overall thickness of the sealabie microphone structure, excluding the microphone, is about 0.5 to 1 mm depending on fabrication methods.

It will be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoin disclosed embodiment. Thus, the claims following are hereby expressly incorporated into this Summary section, with each claim standing on its own as a separate embodiment of this invention. Furthermore, while some embodiments described herein include some but not other features included in other embodiments,, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination,

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details, In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled In the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention. Functionality may be added or deleted from the block diagrams. Steps may be added or deleted to methods described within the scope of the present invention.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in man other forms.

Claims

CLAIMS:

1. A hearing aid device comprising;

a housing,

an input audio transducer disposed within the housing

an aperture extending through the housing wall allowing for a sound wave to pass from the housing exterior to the microphone,

a substantially gas-impermeable diaphragm disposed to cover the

aperture,

a chamber disposed between the microphone and the diaphragm, wherein the diaphragm, chamber and microphone form a substantially gas-tight enclosure,

2. The hearing aid device of claim 1 wherein the diaphragm has an area equal to or less than about 20 mm².

3. The hearing aid device of claim 1 or claim 2 wherein the diaphragm is substantially circular.

4. The hearing aid device of claim 3 wherein the diaphragm has a diameter about 3 mm to about 5 mm.

5. The hearing aid device of an one of claims 1 to 4 wherein the chamber is substantially circular,

6. The hearing aid device of claim 5 wherein the chamber has a diameter of between about 2.7 mm to about 3.3 mm.

7. The hearing aid device of any one of claims 1 to 6 wherein the chamber has a depth as measured from the inner surface of the diaphragm to the chamber floor of between about 100 pm to about 200 pm.

8. The hearing aid device of any one of claims 1 to 7 wherein the chamber floor comprises an aperture configured to convey sound waves from the chamber to the microphone.

9. The hearing aid device of any one of claims 1 to 8 wherein the diaphragm is retained by a force or pressure exerted on the diaphragm.

10. The hearing aid device of claim 9 wherein the force or pressure is applied at one or more points distal to the edge of the aperture to provide an area of diaphragm that is supported by an underlying structure, but is free to vibrate.

11. The hearing aid device of claim 10 wherein the supported area of diaphragm extends between about 1 mm to about 2 mm from the point of application of force or pressure toward the centre of the diaphragm.

12. The hearing aid device of claim 10 or claim 11 wherein the area of diaphragm that is supported by the housing, but is free to vibrate extends at most about 1 mm or about 2 mm beyond the edge of the aperture..

13. The hearing aid device of an one of claims 1 to 12 wherein the diaphragm has a thickness of between about 50 μηι to about 160 μηι.

14. The hearing aid device of any one of claims 1 to 13 wherein the diaphragm has at least 1, 2 or 3 layers.

15. The hearing aid device of any one of claims 1 to 13 wherein the diaphragm has at most 1, 2 or 3 layers.

16. The hearing aid device of any one of claims 1 to 15 wherein the diaphragm consists of or comprises a polymeric material.

17. The hearing aid device of any one of claim 16 wherein the polymeric materia! is a polyester materi l.

18. The hearing aid device of claim 17 wherein the polyester materia! is a polythylene terephthalate or derivative thereof.

19. The hearing aid device of any one of claims 16 to 18 wherein the polymeric material has been modified to increase tensile strength.

2G. The hearing aid device of claim 19 wherein the modification comprises stretching.

21. The hearing aid device of any one of claims 18 to 20 wherein the polythylene terephthalate is a biaxialy-oriented polyethylene terephthalate.

22. The hearing aid device of any one of claims 1 to 21 configured as a behind-the-ear hearing aid device.

23. The hearing aid device of any one of claims 1 to 22 configured as an external component of a cochlear implant hearing aid device.

24. A hearing aid device substantially as hereinbefore described by reference to the drawings,