Ear wax barriers for hearing aids.

0001The present invention relates to ear wax barriers and more particularly to such a barrier for preventing ear wax from entering the sound channel of devices such as hearing aids, for example "in-the-ear" or "canal" type hearing aids or acoustical resonators. The invention also relates to hearing aids including barriers of this type.

0002Most hearing aids include a housing, or shell, that holds the components of the aid. The shell of many aids is designed to rest within the ear canal of a user. The shell of an electronic hearing aid may hold, for example, a microphone, amplification circuitry, and a receiver. The microphone is exposed to sound signals from outside of the aid and responsively creates an electrical signal. The electrical signal may be sent to the amplifying circuitry or other electrical aid components. Such components, in turn, supply a signal to the receiver, and the receiver responsively creates sound.

0003In many electronic hearing aids, the sound travels from an output port of the receiver, through a sound channel in the aid, and out of the aid through an output port in the shell of the aid. The sound from the shell output port may then travel through the user's ear canal and cause the ear drum to vibrate.

0004The ears of most hearing aid users naturally secrete a substance referred to as cerumen or ear wax. While the ear wax cleans the internal structure of an ear, it also tends to flow into the sound channel and receiver of the hearing aid. Upon entering the receiver, the ear wax interferes with, or prevents, the proper operation of the receiver.

0005Small, cosmetic "in-the-ear" and "canal" aids (which typically lay at least partially within the user's ear canal) have recently been developed. With such aids, however, the volume inside of the hearing aid available for components is reduced. This is particularly true when the interior of the user's ear is relatively small. Furthermore, the technology associated with hearing aid manufacture frequently involves fabricating the shell out of plastic. The shell is contoured to the shape of the inner surface of the ear. The thickness of the shell is dictated by the requirement that the shell physically maintain its structural integrity and protect the aid components inside. The wall thickness of the shell, however, reduces the volume inside the hearing aid available for components. The resulting limited volume within the hearing aid available for components generally requires that the receiver be positioned as deep as possible in the user's canal. However, such positioning of the hearing aid within the canal brings the receiver output port into closer proximity to the ear canal environment containing the wax-generating tissue inside the ear canal.

0006While the introduction of in-the-ear and canal aids has improved the acceptance of hearing aids by the hearing-impaired public, such hearing aids have created a problem of dealing with ear wax. As those of the ordinary skill in the art will acknowledge, ear wax migration has been recognized as a difficult problem.

0007The migration of wax into the sound channel and receiver of hearing aids substantially increases the susceptibility of many receivers to clogging. The progressive, gradual clogging of the receiver results in the reduction of acoustic gain and in power output by the receiver, sometimes culminating in the complete failure of the aid to allow output of amplified sound. The degradation or failure of performance of the aid is annoying to the user. When wax blockage occurs, the hearing aid may require complete disassembly so that the receiver may be cleaned or replaced. Of course, bringing the hearing aid to a service centre for disassembly and possible replacement of the receiver is both inconvenient and expensive for the user.

0008A number of presently available systems are poorly suited to guard against ear wax buildup in the receiver of a hearing aid. Some "barrier" designs use a fine mesh screen in the sound channel between the receiver and the outside of the hearing aid. Such screens suffer from the deficiency, however, that if the screen size is made sufficiently small to protect the receiver from wax migration, the screen holes will eventually be clogged by the wax. When mesh is made more coarse, however, wax will not as effectively be prevented from migrating across the screen barrier to the receiver.

0009Alternative systems for preventing wax migration into a receiver include the provision of a single aperture, of a small cross-sectional area, between the receiver and the outside of the aid. Other alternative systems involve the replacement of a cellular synthetic material between the receiver and outside of the aid. Such designs often suffer from the same deficiency in achieving simultaneously both a long-term barrier to wax migration as well as still preventing the clogging of wax over the life of the aid.

0010Porous barriers of the above types generally result in an unsatisfactory compromise between resistance to wax clogging of the barrier itself, on the one hand, and the prevention of wax migration into the receiver on the other. While a small aperture barrier may prevent wax migration, it will also clog. Large apertures may not clog, but they also will not be as effective in blocking wax. Moreover, small pore barriers placed in the pathway between the receiver and the output port of the hearing aid may cause increased acoustic impedance. Increased impedance may result in an undesired change in the frequency response in output pressure levels delivered by the receiver.

0011Primarily, the present invention is directed at an ear wax barrier for a hearing aid, and for illustrative purposes, the invention is particularly described hereinafter in association with an electronic hearing aid. However, it will be understood that the invention can also be used with acoustical resonators, acoustical hearing aids and in other ear related apparatus which would benefit from an ear wax barrier.

0012The invention is concerned with a barrier for ear wax of the kind having a housing with a port for location in acoustic communication with an ear canal. According to the invention, the housing has an interior surface defining an acoustical passage extending from the port with a plurality of projections extending inwardly from the interior surface thereof, the projections being axially spaced and oriented relative to each other to define a tortuous path along said passage.

0013The barrier of the invention is normally preferred for use with a hearing aid or other ear related apparatus including a shell having an acoustic output port to be located in or proximate the user's ear canal. In such embodiments, the housing is adapted to be received by the shell of the apparatus and defines an interior surface around the passage with the axis of the passage substantially aligned with the acoustic output port of the shell. A first projection extends inwardly from the interior surface of the housing, and partially occludes the internal cross-section of the housing, and at least a second projection extends inwardly from the interior surface of the housing, which is spaced along said axis a predetermined distance from the first projection and also partially occludes the interior or the housing, the projections being oriented within the housing to define said tortuous path therethrough. The barrier may include a third projection which extends inwardly from the interior surface of the housing, which is spaced along said axis from the second projection and also partially occludes the housing interior. It will be appreciated that further projections may be included if desired. Embodiments with four and five projections are specifically described hereinafter.

0014Barriers of the invention are conveniently made in such a manner that they are removable from the device in which they are installed for cleaning or replacement. Such embodiments may be threaded such that they may be unscrewed from the device, and/or be provided with a collar to facilitate their removal. A keying mechanism can be used, for example one which enables the use of a screwdriver or like tool to install and remove the barrier from a device.

0015The projections in wax barriers according to the invention may take many forms. Typically, they extend laterally across the housing in the form of plates which directly traverse part of the internal cross-section of the housing, for example disc segments extending around normally at least 180°C. The removed or open portion is typically a right-angular wedge. In another example, the projections take the form of a plurality of spokes extending inwardly from the housing internal surface. If desired, the spokes may converge at the axis of the passage.

0016A typical hearing aid includes a shell and a receiver within the shell. Both the shell and receiver include an acoustic output port. When disposed in such a hearing aid, the housing of a barrier in accordance with the invention interconnects the acoustic output ports of the receiver and shell. Each projection of the barrier partially occludes a portion of the housing interior. Consequently, the projections provide a tortuous path for solid or semiliquid ear wax migrating axially along the inside of the housing. The barrier of the invention can therefore effectively resist wax clogging. Because it substantially blocks the migration of naturally occurring ear wax, it can thereby reduce the clogging of a hearing aid receiver. Additionally, the barrier can present less acoustic impedance to a receiver when placed between the receiver and the acoustic exit port of the hearing aid.

0017Despite its increased effectiveness in the collection of wax, it need not be cleaned nor changed as frequently as known barriers over the life of the hearing aid. Further, it is inexpensive to make and maintain, thereby lowering the cost of hearing aids for consumers.

0018Preferred embodiments of the present invention will now be described with reference to the accompanying drawings wherein: <ul id="ul0001" list-style="none"><li>Figure 1 is a front, partially cut away view of a prior art behind-the-ear hearing aid, in use on a user's ear;</li><li>Figure 2 is a right side, partially cut away view of one preferred embodiment of the present invention, showing an in-the-ear hearing aid with an ear wax barrier, in use within a user's ear;</li><li>Figure 3 is a perspective, partially cut away view of the embodiment shown in Figure 2;</li><li>Figure 4 is a perspective, partial cross-sectional view of the ear wax barrier shown in Figure 3;</li><li>Figure 5 is a perspective, partial cross-sectional view of a first alternative embodiment of the ear wax barrier shown in Figure 4;</li><li>Figure 6 is a perspective, partial cross-sectional view of the embodiment shown in Figure 5, showing a buildup of ear wax after the barrier has been in use within a hearing aid;</li><li>Figure 7 is a perspective, partial cross-sectional view of a second alternative embodiment of the ear wax barrier shown in Figure 4;</li><li>Figure 8 is a perspective, partial cross-sectional view of a third alternative embodiment of the ear wax barrier shown in Figure 4;</li><li>Figure 9 is a perspective, partial cross-sectional view of a fourth alternative embodiment of the ear wax barrier shown in Figure 4;</li><li>Figure 10 is a perspective, partial cross-sectional view of a fifth alternative embodiment of the ear wax barrier shown in Figure 4;</li><li>Figure 11 is a side view of another embodiment of the present invention;</li><li>Figure 12 is a cross-sectional view of the ear wax barrier shown in Figure 11 taken along line 12--12;</li><li>Figure 13 is a partial cross-sectional, partial side view of a hearing aid illustrating the ear wax barrier of Figure 11 incorporated therein;</li><li>Figure 14 is a top view of the ear wax barrier of Figure 11;</li><li>Figure 15 is a partial cross-sectional, partial side view of a mould to produce the ear wax barrier of Figure 11;</li><li>Figure 16 is the cross-sectional view of Figure 11 illustrating a modified projection for the ear wax barrier;</li><li>Figure 17 is a partial top view of the modified projection shown in Figure 16;</li><li>Figure 18 is the cross-sectional view of Figure 11 illustrating the incorporation of an acoustical baffle; and</li><li>Figure 19 is an enlarged, partial and exploded perspective view of the housing an acoustical baffle sown in Figure 18.</li></ul>

0019Figures 2-10 show preferred embodiments of the present invention. Each is an improved ear wax barrier, generally designated 20, for an "in-the-ear" or "canal" type hearing aid, illustratively designated 22.

0020So-called "custom" or generic hearing aids are designed to fit either in the bowl of the ear or, alternatively, in the ear canal itself. Prior to the development of such aids, however, hearing aids were designed to be worn behind the ear of elsewhere.

0021A prior art behind-the-ear hearing aid is shown in Figure 1 and designated 24. The hearing aid, or "aid", 24 included a plastic case 26 to house the hearing aid components. Typical components included a microphone 28, amplifying circuitry (not shown), receiver 30, plastic tubing 32, and ear mould 34.

0022The microphone would receive a sound signal from outside the ear and convert it to an electrical signal. An electrical signal was then responsively transmitted to the receiver 30.

0023The receiver 30 included an acoustic output port 36 interconnected to the tubing 32. Upon receiving signals from the electrical components within the aid 24, the receiver 30 would transmit sound signals through its exit port 36. These sound signals were then conducted, via the tubing, to the ear mould 34 and the interior of the ear of the user.

0024In the prior art embodiment shown in Figure 1, the acoustic exit port 36 of the receiver 30 was physically isolated from the ear environment by the tubing 32. As a result, the migration of the solid or semiliquid ear wax material into the receiver 30 was negligible due to the physical length of the tubing.

0025With the reduction in size of electronic components achieved since 1970 however, more cosmetically attractive hearing aids could be constructed. Such aids fit in the ear or the ear canal of the user. See the aid 22, shown in Figure 2.

0026Like the aid 24 shown in Figure 1, the aid 22 also includes a shell 40 which may also include a microphone 42, amplification circuitry (not shown) and a receiver 44. The shell 40 and receiver 44 each include an acoustic output port, respectively designated 46, 48. The output ports 46, 48 of the shell 40 and receiver 44 are interconnected by a hearing aid sound channel 50. The barrier 20 is positioned in the channel 50 between the two acoustic output ports 46, 48.

0027Again, the microphone 42 receives sound signals and responsively transmits an electrical signal. An electrical signal, in turn, is sent to the receiver 44, which converts it to a sound signal. The sound signal is then transmitted, through the acoustic port 48 of the receiver 44, through the sound channel 50 of the aid 22, to the acoustic exit port 46 in the shell 40 of the hearing aid 22. After leaving the shell 40 of the aid 22, the sound may travel down the ear canal 52 of the user, to the ear drum.

0028As shown in Figure 2, the receiver exit port 48 is in close proximity to the ear canal 52 containing wax generating tissue. As a result, wax frequently migrates through the exit port 46 in the shell 40, upward through the sound channel 50, and into the exit port 48 and the receiver 44 itself. This causes clogging of the receiver 44 or shell port 46, reducing its acoustic gain, power output, and occasionally the complete failure of the aid 22 to amplify or otherwise modify sound.

0029In a preferred embodiment of the present invention, the ear wax barrier 20 is interconnected between the receiver 44 and acoustic exit port 46 of the hearing aid shell 40, as shown in Figure 2. The acoustic output port 48 of the receiver 44 is approximately cylindrical. Thus, the barrier itself is substantially cylindrical, fitting snugly in the shell output port 46. See Figure 3. In other embodiments, of course, that barrier 20 may have any cross-sectional configuration. Thus, for example, the barrier 20 could be made a part of the hearing aid 24. That is, the barrier 20 may be assembled as a part of the shell 40 or as a part of the receiver 44.

0030As shown in Figure 4, one embodiment of the ear wax barrier 20 includes a housing 54 and first, second, third and fourth projections, respectively designated 56, 58, 60, 62. Of course, a lesser or greater number of projections may be used.

0031The housing 54 in this embodiment is substantially cylindrical, defining a wall 64 with first and second ends 66, 68 and comprised of any variety of materials. In the preferred embodiment, injection moulded thermoplastic is used. Examples of materials that might be used to make the housing include "Cycolac", and ABS (Acrylonitrile-­Butadiene-Styrene) resin.

0032The dimensions of the one particular embodiment of the invention are given below.

0033The housing 54 defines a length, between the first and second ends 66, 68, of approximately 0.89 cm (0.35 inch), and the inside diameter of the housing 54 is approximately 0.28 cm (0.11 inch). The thickness of the housing wall is approximately 0.025 cm (0.01 inch), and the housing 54 further defines an interior chamber 70 and an interior surface 72. In addition, the housing 54 defines a central axis of passage 74 between the first and second ends.

0034In the preferred embodiment described herein, the central axis 74 passes through the centre of a roughly cylindrical housing 54, substantially equidistant at all points from the interior surface 72 of the housing 54. The first end 66 fits snugly into the receiver exit port 48. The second end 68, distal from the receiver 44 when in use in a hearing aid 22, faces the acoustic exit port 46 of the hearing aid shell 40 and the interior of the user's ear.

0035As shown, each of the four projections 56-62 is substantially similar to the others. (Of course, a single barrier could also use a variety of differently shaped projections). Only the first projection 56 is discussed in detail below for illustrative purposes.

0036The projection 56 is attached to the interior surface 72 of the housing 54 and extends inwardly toward the central axis 74 of the housing 54. The projection 56 partially occludes the central acoustical passageway or interior housing chamber 70.

0037The projection 56 is typically formed in a thermoplastic that can be injection moulded, just as is the housing 54. In an alternative embodiment, of course, the projection 56 could also be covered with a coating that exhibits a low cohesion to cerumen. Such coatings include, for example, "Teflon" and "Tefzel". Such a coating would make any projection or housing easier to clean after wax has built up upon it.

0038With the housing 54 being cylindrical, the projection 56 defines an outside perimeter 76, a portion of which resembles a circle. Alternatively, the projection 56 may be described as a disc. while the invention encompasses a variety of projection shapes, the preferred embodiment of Figure 4 includes a disc having a wedge-shaped gap 78. In this one preferred embodiment, the projection 56 defines a maximum outside diameter of approximately 0.28 cm (0.11 inch) so that if fits tightly against the interior surface 72 of the housing 54.

0039The projection 56 is attached to the interior surface 72 of the housing 54. Preferably, this is accomplished with strong glue such as a cyanoacrylate ester. In alternative embodiments, however, the projection 56 could be moulded as part of the housing 54, simply press fit into the interior chamber 70 of the housing 54, or otherwise attached to the housing 54.

0040The housing 54 defines an interior circular cross-­sectional area. Again, a portion of the interior is occluded by the projection 56. In the embodiment shown in Figure 4, the projection 56 is in the shape of a disc with a wedge 78 removed. The "removed" portion is described as a "wedge" 78 for purposes of illustration. It is to be understood, of course, that while a wedge typically has only straight sides, the wedge 78 defining an open area in the present context may also include one rounded side missing from the rounded projection 56, shown in Figure 4.

0041Using alternative terminology, the projection 56 may be described as a "270° circle portion". The central axis 74 of the housing 54 defines the centre point of the circle. Also, the "gap" from the projection 56, may be described as a 90° circle portion.

0042The open wedge 78 of the projection 56 defines an open area in the cross-sectional area of the housing 54. Thus, if one were looking through the housing from the first end 66 toward the second end 68, parallel to the axis 74, the interior of the housing 54 would define a circle interior. The projection 56 would block the interior 76 of the housing 54 except for the wedge 78. The first projection 56 itself defines a first occluded area and the wedge 78 defines a first open area in the cross-sectional area of the housing 54, normal to the axis 74.

0043It is through this open area, or wedge 78, in the housing 54 that sound may travel from the receiver 44 to the exterior of the aid 22. If this projection 56 were the only barrier, however, wax, under some circumstances, might flow through the open area. Thus, at least the one additional, second projection 58 is provided to prevent further passage of ear wax.

0044In this illustrated embodiment, the second projection 58 is placed approximately 0.05 cm (0.02 inch) away from the first projection 56. We have found that, in the most preferred embodiments, the projections should be placed apart enough so that the projections will not substantially effect the overall acoustic response and the amount of expected wax buildup will be less than the distance between the projections. Thus, spacing between the projections of 0.0125 to 0.102 cm (0.005 to 0.04 inch) may be used for the most preferred performance of the wax barrier 20.

0045In the preferred embodiment shown, the projections 56-62 are interdigitated within the housing 54, <u style="single">i.e.</u>, the projections are spacially and angularly displaced with respect to the central axis 74. The projections could be made of a variety of substances, such as, for example, thermoplastic or semipermeable material. Of course, the projections may be radially or axially displaced from each other.

0046The second projection 58 is like the first projection 56 in that it defines a second wedge 80. while the second wedge of the preferred embodiment has the same shape as the first wedge 78, the second wedge 80 may, of course differ in size and shape of any other wedge. The second projection 58 and second wedge 80 also define an occluded area and an open area in the housing, normal to the axis 74. The open area of the second projection 58 is positioned over the first occluded area. Thus, a tortuous path is provided for wax which would otherwise migrate from the first end 66 to the second end 68.

0047In the embodiment shown in Figure 4, the wedges 78, 80 measure approximately 90°. The second projection 58 is similar to the first projection 56 in design, but has been rotated clockwise 90° from the position of the first projection 56. Finally, the fourth projection 62 has been rotated 90° in a clockwise direction from the position of the third projection 60. The open area of each projection is further blocked, or occluded, by occluding portions of three other projections. The interdigitated projections thus cooperate to completely occlude the acoustical passageway 70 against wax migration. That is, every line of migration through the housing 54 along the interior surface 72 is interrupted by a projection. Applicants have found that such a construction provides a tortuous path for ear wax, substantially reducing the amount of ear wax that may migrate from the sound channel 50 to the receiver 44 while at the same time providing substantially little acoustic impedance to the receiver 44.

0048A second embodiment of the invention is shown in Figure 5. The barrier 82 includes a housing 84 and a multiplicity of projections. The barrier 82 includes first, second, third, and fourth projections 86, 88, 90, 92. Construction of the housing 84 is similar to that shown in Figure 4. Also, the projections 86-92 are of substantially the same thickness and positioned substantially the same distance apart as the embodiment shown in Figure 4. However, rather than being 270° circle portions, each projection is substantially a 180° circle portion (or semicircle).

0049The first projection 86 again defines a first occluded area and a first open area. The second projection 88 has been effectively rotated such that the occluded area of the second projection blocks the open area of the first projection 86. The third projection 90 blocks the open area of the second projection 88. Similarly, the fourth projection 92 blocks the open area of the third projection 90.

0050As shown in Figure 6, such an arrangement of 180° circle portion projections 86-92 prevents wax from flowing directly through the housing 84. A substantial buildup of wax 94 may be anticipated on the first projection over the life of the hearing aid 22. The second projection 88 may be expected to receive a lesser amount of wax buildup 96, since it is positioned slightly deeper into the housing 84. The third projection 90, however, experiences substantially smaller amounts of wax buildup 98, since the path for wax migration has been blocked by the first and second projections 86, 88. The fourth projection 92 receives even less wax buildup, because of the wax already blocked by the first three projections 86-90.

0051Another embodiment of the invention is shown in Figure 7. The barrier 100 again includes a housing 102 and a multiplicity of projections 104, 106, 108, 110. The housing is substantially similar to that shown in Figures 4-6.

0052Each of the four projections 104-110 is comprised of a series of 24 spokes 112, 114, 116, 118, radiating from central points 120, 122, 124, 126 defined by the central axis 128. Each spoke is approximately 0.025 cm (0.01 inch) diameter. The projections 104-110 are again made of a plastics material, and the second projection 106 is effectively rotated a few degrees from the position of the first projection 104. In turn, the third projection 108 has been rotated slightly from the position of the second projection 106, and the fourth projection 110 has a position rotated slightly from the position of the third projection 108.

0053Another alternative embodiment is shown in Figure 8. In this embodiment, the barrier 130 includes a housing 132 and first, second, third, fourth, and fifth projections, 134, 136, 138, 140, 142. Each of the projections 134-142 comprises approximately a portion of a circle portion. The second projection 136 has been rotated from that of the first projection 134. The third, fourth and fifth projections 138-142 are similarly rotated from the position of each previous projection. When the housing is viewed from the direction of the arrow of the axis 144 shown in Figure 9, the entire internal cross-sectional area of the housing is again blocked by the projections 134-142.

0054The plurality of projections 134-142 have approximately the same thickness and displacement along the axis 144 as the projections previously described for the embodiments shown in Figures 4-7. There are five, rather than four, projections however. Thus, the housing 132 is approximately 0.05 cm (0.02 inch) longer than the housing 54 shown in Figure 4.

0055Yet another embodiment is shown in Figure 9. Like the embodiment of Figure 5, the barrier 146 includes a housing 148 and a plurality of projections 150, 152, 154, 156, and each of the projections 150-156 are approximately 180° circle portions. However, each projection is rotated approximately 90° (rather than 180°) from the preceding projection. Thus, the second projection 152 has been rotated approximately 90° from the position of the first projection 150. The third and fourth projections 154, 156 are also rotated approximately 90°.

0056A further embodiment of the invention is shown in Figure 10. Each of the projections 160-166 comprises approximately a 90° circle portion. The second projection 162 has been rotated approximately 90° from the position of the first projection 160. Similarly, the third projection 164 is rotated approximately 90° from the position of the second projection 162. The fourth projection 166 has a position which is rotated approximately 90° from the position of the third projection 164.

0057A yet further embodiment of the invention is shown in Figures 11-15 as an ear wax barrier 200 for a hearing aid 202. As best shown in Figure 13, the hearing aid 202 includes a shell 204 adapted to be inserted in an ear channel (not shown) and defining an acoustical outlet port 206. The hearing aid 202 further includes a receiver 208 having a receiver outlet port 210.

0058In this embodiment, the receiver 208 is secured within the shell 204 by an elastomeric filling 212. That is, the receiver 208 is positionally set with respect to the shell 204 and then embedded in the filling 212. Once to filling 212 cures, the receiver 208 is secured as well protected by the pliable, shock-absorbing filler 212.

0059The shell 204 includes an internally threaded opening 214 which interconnects the acoustical outlet port 206 with the interior chamber 216 of the shell 204. This opening 214 is adapted to receive the ear wax barrier 200. As best shown in Figure 13, the shell 204 is filled in such a manner that the elastomeric filler 212 defines a substantially cylindrical channel 218 immediately adjacent the receiver outlet port 210 and an internally-­threaded cavity 220 immediately adjacent and extending the opening 214 into the interior chamber 216.

0060The ear wax barrier 200 is an integral piece of moulded thermoplastic material, such as ABS. The barrier 200 includes a substantially cylindrical housing 222 defining a central acoustical passageway 224 between a barrier inlet port 226 and a barrier outlet port 228. The housing 222 has an externally-threaded portion 230 and a collar portion 232, which defines the outlet port 228. As shown, the outer diameter of the collar portion 232 is slightly greater than the outer diameter of the externally-threaded portion 230.

0061The housing 222 is adapted to be received by the internally-threaded opening 214 of the shell 204, as extended by the filler 212. Secured therein, the central axis 234 of the housing 222, or more particularly the central acoustical passageway 224, substantially aligns with the receiver outlet port 210. The barrier inlet port 226 aligns with and slightly overlays the channel 218, such that audio signals produced by the receiver 208 are received by the barrier 200 and pass through the acoustical passageway 224. That is, the passageway acoustically links to receiver 208 to the outlet 206 of the hearing aid 202.

0062In this preferred embodiment, the collar portion 232 of the housing 222 includes diametrically opposed slots 236A, 236B, extending from the substantially cylindrical barrier outlet port 228. These slots 236A, 236B cooperate to define key means, generally designated 238, for rotating the ear wax barrier 200 with an instrument (not shown) having a screwdriver-like configuration. Utilizing the key means 238, the ear wax barrier 200 can be readily removed from the shell 204 for cleaning or replacement.

0063The ear wax barrier 200 or more particularly the externally-threaded portion 230 of the housing 222 includes an access opening 240. As best shown in Figures 11 and 12, the access opening 240 is substantially rectangular and substantially centrally located in the externally-threaded portion 230. The access opening 240 provides direct access to the passageway 224 for inspection and cleaning.

0064Referring now to Figures 12 and 14, the ear wax barrier 200 also includes at least two substantially semi­circular projections 242A, 242B, which extend into the passageway 224. The projections 242A, 242B are equally spaced from each other and from the barrier inlet port 226 and outlet port 228 and are substantially perpendicular to the central axis 234 and the interior wall surface of the housing 222. In this preferred embodiment, the projections 242A, 242B extend slightly beyond the midline "ML" of the collar portion 232 (as shown best in Figure 14), such that the projections 242A, 242B slightly overlap.

0065The projections 242A, 242B (here and in the other preferred embodiments) interrupt the central acoustical passageway 224 such that the migration of ear wax is retarded. The projections 242A, 242B cooperate to define trap means, generally designated 244, for accumulating ear wax in predetermined accumulation sites 246A, 246B, thereby retarding flow through the central acoustical passage 224 without substantial interference with the performance characteristics of the hearing aid 202. A best shown in Figure 14, the accumulation sites 246A, 246B, in cooperation, extend completely about the interior wall surface of the housing 222.

0066The ear wax barrier 200 is moulded in a five-part mould 248 shown in Figure 15. The mould 248 incudes mould halves 250A, 250B adapted to receive first, second and third inserts 252A, 252B, 252C. As shown, the three inserts 252A, 252B, 252C cooperate to define the central acoustical passageway 224 and access opening 240.

0067Referring now to Figures 16 and 17, a modified configuration for the projections 242A, 242B is shown. (Only one projection 242A is discussed herein for simplicity.) The projection 242A includes a disc portion 254 and a flange portion 256. The disc portion 254 is identical to the projection 242A described above and shown in Figures 12-15. The disc portion 254 defines a terminus edge 258.

0068The flange portion 256 extends from the terminus edge 258, substantially perpendicular to the disc portion 254. The flange portion 256 extends away from the receiver 208 and towards the acoustical outlet port 206 of the shell 204. The flange portion 256 creates further impedance to the migration of wax through the barrier 200 and cooperates with the disc portion 254 to define the trap means 244.

0069The disc portion 254 includes a series of depression or "dimples", generally designated 260, which further retard wax migration by providing additional accumulation sites. In essence, migration is retarded since the depressions 260 must at least partially filled before further advancement occurs.

0070The projection 242A shown in Figure 16 offers an additional advantage. The configuration of the disc portion 254 and flange portion 256 provides an adjustable acoustic damping means and may, with proper dimensioning, provide substantially optimum damping of the overall frequency response, in combination with the wax barrier 200. In one embodiment, the flange portion 256 is connected to the disc portion 254 by a "living hinge". The orientation of the flange portion 256 is adjusted to provide a variably constricted acoustic pathway, thus providing the desired acoustic damping in combination with the wax barrier 200. Once properly positioned, the flange portion 256 is secured to the interior wall surface of the housing 222 by gluing or other means.

0071As shown in Figures 18 and 19, the ear wax barrier 200 may also include an adjustable acoustical baffle 262. The adjustable baffle 262, or "variable acoustic attenuator", includes a central, substantially cylindrical section 264 and a pair of wing sections 266A, 266B, which extend in opposed relationship from the central section 264. Each of the wing sections 266A, 266B is substantially rectangular and thin. The adjustable baffle 262 mounted on opposed pins 268A, 268B which extend from the interior wall surface of the housing 222 and engage the channel 270 defined by the central section 264. The orientation of the adjustable baffle 262 may be set by gluing or by mated, interlocking tabs 272 on the interior wall surface of the housing 222, equally spaced about the pins 268A, 268B, and slots 274 equally spaced about the ends of the central section 264 of the adjustable baffle 262. The adjustable baffle 262 includes an adjustment aperture 276, centrally located along one side of one of the wing sections 266A, 266B. The open areas 278A, 278B between the adjustable baffle 262 and the projections 242A, 242B provide a constricted passageway for damping of the overall acoustic response.

0072In each of the embodiments described, a tortuous path is provided to effectively reduce wax migration. Moreover, in some instances, the barrier may include means for adjusting the overall acoustic damping in combination with the wax barrier 200. Nonetheless, substantial open areas are provided to reduce acoustic impedance by the wax barrier. In each of the preferred embodiments, the cross-­sectional area of the housing is substantially blocked off by one or more projections.

0073In the preferred embodiments of the invention described above, the wax barrier 30 is placed in the sound channel 50 or otherwise positioned between the output port 46 of the hearing aid shell 30 and the output port 48 of the receiver 44. Such positioning allows the barrier 20 to block wax from entering the receiver 44 from the outside of the hearing aid 22. Of course, it is understood that, as an alternative embodiment the wax barrier 20 may be interconnected directly to or into the output port 48 of the receiver 48.

0074Although wax barriers of the invention are described above in combination with hearing aids, they could be used in combination with other audio devices which are subject to deterioration in performance as a consequence of ear wax buildup.