WO2013016589A1

WO2013016589A1 - Hearing aid for non-contact eardrum pressure activation

Info

Publication number: WO2013016589A1
Application number: PCT/US2012/048418
Authority: WO
Inventors: Armand P. Neukermans
Original assignee: Neukermans Armand P
Priority date: 2011-07-26
Filing date: 2012-07-26
Publication date: 2013-01-31
Also published as: WO2013016589A4

Abstract

A hearing aid system (10) includes an acoustic driver (24, 23, 28 or 84, 82) that is located at the distal end of the external ear (12) canal furthest from the auricle (14) in close proximity to the eardrum (16) for stimulating the eardrum (16) acoustically. The hearing aid system (10) also includes an acoustic-absorbing stop (34) juxtaposed with the acoustic driver (24, 23, 28 or 84, 82} that is located distal from the eardrum (16), An excitation means (62) included in the hearing aid system (10) energizes operation of the acoustic driver (24, 23, 28 or 84, 82) responsive to an electrical signal received from a microphone (42) that converts sound impinging upon the auricle (14) into the electrical signal.

Description

REARING AID FOR NON-CONTACT EARDRUM PRESSURE ACTIVATION

Technical Field

The present disclosure relates generally to the technical field of hearing aid systems and, more particularly, to hearing systems that enable or enhance an individual's ability to hear by stimulating the tympanic membrane with sound.

Background Art

Most hearing aids are activated by an acoustic transducer, producing sound in the open ear canal (occasionally using a sound tube) . These sound waves activate the eardrum, which in turn, drives the ossicles in the middle ear, eventually stimulating the hair cells in the cochlea. However, some systems, such as the ear lens developed by R. Perkins, are envisioning driving the eardrum directly using external activation, with activation energy supplied by various means (magnetic or photonic) .

In some implantable hearing aids, most notably the one developed by Lesinski and Neukermans, directly stimulate the fluid in the cochlea acoustically. These fully implantable hearing aids use a fluid filled piezo transducer of small size which has a distal tube and membrane suitable for penetrating the cochlear wall. Transducers of the type disclosed by Lesisnki and Neukermans have extraordinarily flat and wide frequency response, greater than 10 KHz.

An object of the present disclosure is to provide an improved hearing aid system for placement in the external ear canal that stimulates the tympanic membrane acoustically rather than mechanically.

An object of the present disclosure is to provide an improved hearing aid system for acoustically stimulating the tympanic membrane which locates its acoustic driver in the external ear canal in close proximity to the eardrum.

An object of the present disclosure is to provide an improved hearing aid system located in the external ear canal for acoustically stimulating the tympanic membrane that an individual can easily insert or remove at will .

Briefly_., the disclosed hearing aid system includes an acoustic driver that is located at the distal end of the external ear canal furthest from, the auricle in close proximity to the eardrum for stimulating the eardrum acoustically. The hearing aid system also includes an acoustic -absorbing stop juxtaposed with the acoustic driver that is located distal from the eardrum. An excitation means included in the hearing aid system energizes operation of the acoustic driver responsive to an electrical signal received from a microphone? that converts sound impinging upon the auricle into the electrical signal .

In a first embodiment of the hearing aid system the audio driver includes a piezoelectric transducer that is located outside of the external ear canal. Displacements of this piezoelectric transducer are coupled, via a liquid filled tube, to a balloon that is located in close proximity to the eardrum. In a second embodiment of the hearing aid system a piezoelec- trie driver that is located in the external ear canal in close proximity to the eardrum provides the system's audio driver.

These and other features , objects and advantages will be understood or apparent to those of ordinary skill in the art from the following detailed description of the preferred embodiment as illustrated in the various drawing figures.

Brief Description of Drawings

PIG. 1 is a schematic coronal view through a human temporal bone illustrating the external, middle and inner ears, and showing the relative positions of one embodiment of a hearing aid system that includes a transducer connected via a tube to a balloon that is located in the external e

close proximity to the eardrum;

FIG. 2 illustrates schematically in greater detail the hearing aid system depicted in FIG. 1;

FiGs . 3A and 3B depict a prior art fluid piezo driver that may be advantageously adapted for use in the hearing aid system depicted, in FIGs, i and 2; PIG. 4 is plan -view of a spoked support ring located along the length of the tube for centering the tube within the external ear canal.;

FIG. 5A is a cross-sectional view depicting one end of the hollow tube and the .balloon that is located in close proximity to the eardrum;

FIG . SB is a plan view of an acoustic-absorbing stop that encircles the tube immediately adjacent to the balloon;

FiGs . 6A and 6B are cross-sectional elevational views depicting an alternative embodiment transducer for use. in the. hearing aid system that omits the fluid filled tube? and balloon, and instead locates the transducer in close proximity to the eardrum; and

FIG. 7 is a schematic, cross- sectional diagram, similar to the illustration of FIG. 2, depicting a hearing aid system that includes a transducer of the type depicted in FIG. SB with the transducer located within the external ear canal in close proximity to the eardrum. Best Mode for Carrying Out the Disclosure

It is known that the human eardrum requires very little displacement to perceive an audible sound. For example, at the threshold of hearing 10^"i2W/m², the displacement of the eardrum is approximately lO^*3 ran. At the threshold of pain i.e. acoustic power of iw/m^a, the displacement is 10³ ran or 1.0 μηι. At audio frequencies, such displacements are easily replicated and forced with commercially available? piezoelectric transducers .

FIG. 1 illustrates one embodiment of hearing aid system in accordance with the present disclosure identified by the general reference character 10. As illustrated in FIG, 1, the disclosed hearing aid system 10 is adapted for placement at least partially into an external ear canal 12 of a human. The illustration of FIG. 1 depicts an auricle 14 at one end of the external ear canal 12 and an eardrum 16 {tympanic membrane) at an end of the external ear canal 12 distal from the auricle 14. The embodiment of the hearing aid system 10 depicted in FIG. 1 includes a transducer housing 22 that encloses a piezoelec- trie transducer 24. The transducer 24 might be of a type illustrated in FIG. 3Ά and 3B and described in United States Patent no. 6,068,589 that is hereby incorporated by reference as though fully set forth here. The transducer 24 connects via a generally rigid, fluid filled tube 26 to an acoustic driver located in close proximity to the eardrum 16 which, in the embodiment depicted in FIG. 1, is a balloon 28. As best illustrated in FIG. 1, the tube 26 is suitably curved to follow the shape of the external ear canal 12.

The tube 26 of the. hearing aid system 10, more clearly illustrated in FIG. 2, preferably includes short flexible sections 32, perhaps provided by soft rubber or metal bellows. The flexible sections 32 attenuate any impacts received by the transducer housing 22, and ensure that no excess pressure can be applied to the eardrum 16. An acoustic-absorbing stop 34 is juxtaposed with the balloon 28 distal from the eardrum 16 to attenuate sound at the eardrum 16 from reaching a microphone 42 that is preferably attached along the length of the tube 26. The microphone 42 (preferentially directional towards the aux'icle 14 and bi-directional if desix'ed) is preferably located along the length of the tube 26 within the external ear canal 12 in an optimum position for receiving sound that impinges upon the auricle 14. Disposed in this location the microphone 42 receives natural, virtually undisturbed sound practically the same as if the tube 26 were not px'esent within the external ear canal 12. Note that the microphone 42 should receive only sound coming into the external ear canal 12 from the auricle 14, and should be acoustically isolated from the tube 26 to avoid picking up other vibration (s) . Rejecting vibrations other than sound entering the external ear canal 12 via the auricle 14 can be further enhanced by including a dummy microphone or an accelerometer {not depicted in any of the FIGs . } that is unresponsive to incoming sound and that provides a signal useful, for canceling non- sound vibrations received by the microphone 42. The hearing aid system 10 also includes wires 44 preferably secured to the tube 26, that connect the microphone 42 to the transducer housing 22. The hearing aid system 10 preferably includes a pair of mostly open, support rings 52, better illustrated in the plan view of FIG. 4. The support rings 52 are disposed along the length of the tube 26 for centering the tube 26 within the external ear canal 12, As illustrated in FIG. 4, each of the support rings 52 includes an outer rim 54 that contacts the external ear canal 12 with thin radial spokes 56 extending inward to a circular loop 58 that encircles the tube 26. The radial spokes 56 may be stiff in the longitudinal direction, i.e. along the length of the tube 26 and the external ear canal 12. The openness of the support rings 52 permits sound to enter the external ear canal 12 virtually impeded.

The hearing aid system 10 also includes driving electronics and battery 62 illustrated in FIGs. 1 and 2 which may be located behind the auricle 14, and connects to the transducer 24 by wires 64. Alternatively, the driving electronics and battery 62 may be integrated within the transducer housing 22.

Transducers of the type described in United States Patent no. 6,068,589 and illustrated in FIGs. 3A and 3B includes piezoelectric elements that press on thin membranes thereby, if included in the hearing aid system 10, squeezing fluid in and out. of an exit tube. Use of a symmetric drive disposed along opposite sides of the transducer reduces spurious vibrations that could be coupled to the tube 26. These transducers exhibit extremely high and flat frequency response i.e. well over 10 kHz and above. It has been known for a very long time that faithful or enhanced sound reproduction of high frequencies is very desirable for increasing speech comprehension. This type of transducer may include one or two piezo- electric elements operating in tandem to produce the desired fluid motion. The transducers might be from a few mm to well over 1.5 cm in size, and can be arranged to connect with the tube 26 at any angle. As described in United States Patent no. 6,068,589, the tube 26 and the transducer 24 are both filled with an incompressible liquid such as saline water, silicone oil, etc. having a low viscosity. Gaseous bubbles should not be ρχ-esent in the transducer 24 or the tube 26 as their compression reduces sound transmission efficiency. FIG. Sh schematically depicts the balloon 28, or alternatively a bellows. The impervious balloon 28 can be made out of thin, very flexible polymeric material such as silicone, polyivnide etc, preferably any material that is known to avoid allergic reactions to tissues of the external ear canal 12, The balloon 28 may include an internal very thin wire cage 68 to ensure, similar to a stent, that the balloon 28 maintains free standing support and permanent shape that generally matches the conical eardrum 16 thereby establishing a somewhat cylindrical cavity between the balloon 28 and the eardrum 16. The back of the balloon 28 furthest from the eardrum 16 is rigid to project deformation of the balloon 28 toward the eardrum 16.

Note that the activating the transducer 24 may emit a small amount of sound which could result via the microphone 42 in undesirable audio feedback. However, such undesirable emissions may be attenuated either fay acoustic isolation within the transducer housing 22 that surrounds the transducer 24, or by techniques well known as used in noise reducing microphones (e.g. by canceling the sound with drivers of opposite movements) . The motion of the fluid itself in the tube 26 is almost free of sound. Sound emanating near the eardrum 16 can likewise be attenuated with the acoustic -absorbing stop 34. As best illustrated in FIG. 5B, the acoustic-absorbing stop 34 includes a low pass filter, i.e. a small tubular hole 72 well known in the art, allowing the air to equilibrate in the. small cavity between the plug and the eardrum 16, but effectively preventing sound from escaping past the acoustic-absorbing stop 34.

The tube 26 is preferably made from small, thin-walled rigid tubing, e.g. 1 mm in diameter either of metal or plastic. The tube 26 conducts liquid motion to the balloon 28 which is carefully positioned in close proximity to but not contacting the eardrum 16, anywhere from 100 urn to a few mm from the eardrum 16. Energizing the transducer 24 alternatively expands and contracts the balloon thereby generating pressux'e changes in the space between the acoustic-absorbing stop 34 and the eardrum 16, These pressure changes stimulate in the natural way the human auditory pathway.. An advantage of this non-contact method for stimulating the auditory pathway is that the eardrum, which is susceptible to various complex modes of operation, is excited naturally by uniform changes in pressure. To create a sound level of 96 dB, the pressure excursion must be 1 Pascal RMS, or 10^'s atmosphere. A compression of 10^"K of the volume of the acoustic cavity will create this pressure. For a cavity that is 3.0 mm in diameter x 1.0 mm high, and a balloon 28 that is 3.0 mm in diameter, lateral extension of the balloon 28 need only foe 10^-5 of 1.0 mm, to create this pressure. A 10^'5 of 1.0 mm displacement of the balloon 28 requires a liquid volume displacement of 70 μην which is easily accomplished with transducers of the type described in United States Patent no. 6, 068, 589. Very little mass needs to be displaced for this movement of the balloon 28, hence the balloon 28 exhibits little vibration. This lack of movement assists in isolating the microphone 42 from movement of the balloon 28. The balloon 28 requires no particular shape, but the cavity between the acoustic-absorbing stop 34 and the eardrum 16 should be minimized, e.g. by suitable shaping of the balloon 28. The smaller the effective cavity, the smaller the volume of liquid that must .be displaced within the tube 26 to effect, a specified pressure change at the eardrum 16.

While the hearing aid system 10 depicted in FIG. 1 and 2 uses liquid coupling between a transducer 24 located outside the external ear canal 12, a small, low mass transducer making sound and creating uniform pressure excursions in the confined, acoustically blocked space between the acoustic-absorbing stop 34 and the eardrum 16 may alternatively be used for acoustical- ly stimulating the tympanic membrane . PIGs . 6A, 6B and 7 depict such an alternative embodiment for implementing the hearing aid system 10. Those elements depicted in FIGs . 6A, 6B and 7 that are common to the embodiment of the hearing aid system 10 illustrated in FIGs. 1 and 2 carry the same reference numeral distinguished by a prime {" } designation.

In the illustration of FIG. 6A, a piezoelectric transducer 82 mounted within a closed transducer case 84 provides an acoustic driver located in close proximity to the eardrum 16' - δ - to generate pressure variations in the space between the acoustic-absorbing stop 34* and the eardrum 16*. In the configuration depicted in FIG. 6Ά, the piezoelectric transducer 82 mounted within the transducer case 84 acts like a piston creating pressure variations in the space surrounded by a section of the external ear canal 12' and located .between the acoustic-absorbing stop 34' and the eardrum 16'. Configuring the piezoelectric transducer 82 and the transducer case 84 in this way eliminates any need for the liquid filled tube 26 depicted in FIGs . 1 and 2 that extends between the transducer 24 and the balloon 28. If necessary, vibration of the transducer case 84 may be reduced by including an identical, second piezoelectric transducer within the transducer case 84 that is energized to move in a direction that is opposite to movement of the piezoelectric transducer 82.

For lowest drive requirements and hence minimum vibration the space between the piezoelectric transducer 82 and the eardrum 16 ' should be minimized. For example, assuming a cylindrical geometry with the size of the piezoelectric transducer 82 approximately the same as that of the eardrum 16 ' , if the distance between the piezoelectric transducer 82 and the eardrum 16' were 0,1 mm a 96 dB stimulation of the eardrum 16' corresponds to 1.0 Pascal for which displacement of the piezoelectric transducer 82 need only to 0.1 * 10^-5 mm. Since the piezoelectric transducer 82 is minimally loaded, very thin piezoelectric material may be used which reduces both the. power required, for driving the piezoelectric transducer 82 and the acoustic power that may leak to the transducer case 84 ' .

Because the piezoelectric transducer 82 is flat while the eardrum 16' has a mainly conical shape, the piezoelectric transducer 82 may advantageously be covered with a very light, closed, elastic cap 88 depicted in FIG. SB that is shaped to match the conical shape of the eardrum 16' . The presence of the cap 88 establishes an approximately cylindrical cavity between the cap 88 and the eardrum 16' thereby reducing the space surrounded by a section of the external ear canal 12* and located between the acoustic -absorbing stop 34 ^! and the eardrum 16 · . FIG. 7 depicts schematically an implementation of the hearing aid system 10 using the piezoelectric transducer 82 and cap 88 depicted in FIG. 6B. In the implementation depicted in FIG. ?, the transducer case 84 carrying the piezoelectric transducer 82 and the cap 88 is attached to one end of a support tube 92 , A key 94 attached to the opposite end of the support tube 92 together with a tool (not illustrated in any of the FIGs.) that mates with the key 94 are used to position the alternative embodiment hearing aid system 10· within the external ear canal 12*. The two (2) support rings 52' locate, the transducer case 84 carrying the piezoelectric transducer 82 and the cap 88 uniquely in the external ear canal 12 ' . The microphone 42* is isolated to the extent possible from vibrations of the support tube 92 to minimize feedback from the piezoelectric transducer 82. The acoustic-absorbing stop 34' impedes sound diffusion from the piezoelectric transducer 82 to the microphone 42 ^> . If advantageous, the hearing aid system 10 may include one or more additional acoustic-absorbing stops to further attenuate sound diffusing from the piezoelectric transducer 82 to the microphone 42'. Such additional acoustic-absorbing stops may be advantageously incorporated into the support rings 52 ' nearest the transducer case 84 , As illustrated in FIG. 7, the hearing aid system 10 includes wires 64^» that extend along the support tube 92 for connecting the microphone 42 ' and the piezoelectric transducer 82 to the driving electronics and battery 62' which may be located behind the auricle 14 ^! .

Alternatively, since little energy is required to operate the alternative embodiment hearing aid system 10, a wireless configuration for the hearing aid system 10 that eliminates the wires 64' becomes feasible. For a hearing aid system 10 having a wireless configuration, a small battery would be included on the support tube 92 together with some driving electronics for the piezoelectric transducer 82 and receiving electronics for the microphone 42'. The driving electronics and battery 62' could then be located behind the auricle 14 or somewhere else in close proximity to the support tube 92 to exchange wireless signals with the electronics mounted on the support tube 92. Industria1 Appliea.biiity

Due to individual anatomical differences, both embodiments of the hearing aid system 10 described above must be fitted to an individual. Fitting the hearing aid system 10 to an individual begins with making an imprint of their external ear canal 12, Then the tube 26 or the support tube 92 is suitably curved to follow the shape of the external ear canal 12 followed by precisely locating the support rings 52, 52' , If the embodiment of the hearing aid system 10 depicted in FIGs. 1 and 2 is being fitted to an individual and if one of the. flexible sections 32 is located near the auricle 14, that end of the tube 26 can be made rigid for insertion into the external ear canal 12 by a clamp which is removed after insertion. During insertion of the balloon 28 or the transducer case 84 carrying the piezoelectric transducer 82 and cap 88 into the external ear canal 12, the hearing aid system 10 produces a suitable tone with the perceived sound rising quadratically with decreasing separation between the eardrum 16 and either the balloon 28 or the transducer case 84 carrying the piezoelectric transducer 82 and cap 88. Guided by the tone and the support rings 52, an individual can monitor the progress of insertion, and terminate insertion of the hearing aid system 10 unambiguously in the proper location without damage to the eardrum 16 or the hearing aid system 10. Thus, the hearing aid system 10 is advantageously amenable to an individual's self insertion and removal of the hearing aid system 10 at will.

While both embodiments of the hearing aid system 10 have been described as using a piezoelectric transducer, those skilled in the relevant art. will recognized that other types of light weight electromagnetic or electrostatic transducers might be substituted in the hearing aid system 10 for the piezoelectric transducer (s) .

The driving electronics and battery 62 included in either embodiment of the hearing aid system 10 can be of any type- known to be useful for receiving an electrical signal from the microphone 42 and supplying a driving electrical signal to the piezoelectric transducer 24, 82. Although the present invention has been described in terms of the presently preferred embodiment , it is to be understood that such disclosure is purely illustrative and is not to be interpreted as limiting. Consequently, without departing from the spirit and scope of the disclosure, various alterations, modifications, and/or alternative applications of the disclosure will, no doubt, be suggested to those skilled in the art after having read the preceding disclosure. Accordingly, it is intended that the following claims be interpreted as encompass- ing all alterations, modifications, or alternative applications as fall within the true spirit and scope of the disclosure?.

Claims

The._.Claimg_ What is claimed is:

1. A hearing aid system (10) adapted for placement at least partially into an external ear canal (12} of a human, the external ear canal (12} having an auricle (14} at one end thereof and an eardrum (16) (tympanic membrane} at an end of the external ear canal (12} distal from the auricle (14) , the hearing aid system (10) comprising:

a. an acoustic driver (28, 82} for placement at the. distal end of the external! ear canal (12) in close proximity to the eardrum (16) for stimulating the eardrum (16) acoustically;

b. an acoustic-absorbing stop (34, 34'} juxtaposed with the acoustic driver (28, 82) and distal from the eardrum (16) ;

c. excitation means (24 & 62, 62'} for energizing operation of said acoustic driver (28, 82) ; and d. a microphone (42) for converting sound impinging upon the auricle (14) into an electrical signal that is supplied to said excitation means {24 & 62, 62'} ,

2. The hearing aid system (10) of claim 1 wherein said acoustic driver (23, 82} includes:

i. a transducer (24) for placement outside the external ear canal (12);

ii. a rigid tube (26) filled with liquid that moves in response to displacements of said transducer (24) ; and

iii. a balloon (28) for placement in the external ear canal (12) in close proximity to the eardrum (16) that receives via the tube (26) displacements of said transducer (24) for stimulating the eardrum (16) acoustically.

3. The hearing aid system (10) of claim 1 wherein said acoustic driver (28, 82} includes: a transducer case (84) for placement within the external ear canal (12) distal from the auricle (14) ;

11. a transducer (82) carried within said transducer case (84) at an end thereof that is nearest the eardrum. (16) for placement in close proximity to the eardrum (16) for stimulating the eardrum (16) acoustically; and in . a support tube (92) attached to an end of said transducer case (84} that is furthest from the eardrum (16) , the support tube (92) facilitating placement of said transducer case (84) carrying said transducer (82) at the proper location within the external ear canal (22) ,

4. The hearing aid system (10) of claim 3 further comprising a elastic cap (88) that is attached to an end of said transducer case (84) that is nearest the eardrum (16) and covers said transducer (82), said cap (88) being shaped to match the shape of the eardrum (16) ,

5. The hearing aid system. (10) of any one of claims 1 through 4 wherein said microphone (42) is located within the external ear canal (12) between the acoustic-absorbing stop (34, 34') and the auricle (14) ,

6. The hearing aid system (10) of any one of claims 1 through. 4 further comprising at least one support ring (52) through which said tube (26, 92) passes for positioning said tube (26, 92) within the external ear canal (12) .