Hearing aid

21~8 ~54 6~17~7\ ~Cl/US~4(;71 HEARING AID .

BACKGROUND OF THE INVENTION 1.

Field of the Invention:

The present invention relates to hearing aids.

In particular, the present invention relates to a hearing aid having a microphone worn in 10 the conchal bowl of the external ear, an amplifier and power source disposed behind the ear, and a sound conductor running from the housing behind the ear through the soft tissue of the external auditory canal and into the auditory canal medial to the cerumen-producing portion of the canal.

The invention further relates to a method for installing said 15 hearing aid.

2.

Discussion of Background:

The human auditory system includes the outer ear (the auricle or pinna), an auditory canal .o.xf~nriin~ inwardly towards an ear drum or tympanum, a middle ear and an inner ear.

The outer ear serves as a 20 collecting dish for sound waves, which are then directed into the auditory canal toward the ear drum.

Sound is perceived when the vibrations caused by sound waves are transmitted by the ear drum through the bones of the ossicular chain in the middle ear to the cochlea in the inner ear.

The cochlea produces electrical impulses that are L,~ rd to the brain 25 through the auditory nerve.

WO 95/17078 2 1~ 8 7 5 ~ pCT/US94/14674 An estimated 15% of the population (about 40% of the elderly population) have impaired hearing and could benefit from the use of hearing aids.

Most users of hearing aids are fitted with conventional aids of the "air conduction" or "bone conduction" type.

Air conduction 5 devices work by collecting incoming sound with a rnicrophone, amplifying the sound and delivering the amplified signal by way of a speaker positioned in the outer portion of the ear canal.

Amplifiers may be placed behind the ear or in the ear canal, as in the devices shown by Geers (U.S.

Patent 5,048,090) arld Wullstein (UK Patent 962,780).

Bone 10 conduction aids convert the incoming sound signal into mPl`.hAniCAl vibrations that are tld~ rd to the bone structure of the skull.

The resulting vibration of the skull s~imlllArPs the cochlea, resulting in a perceived sound.

Implantable hearing devices offer some benefits in specific clinical lS situations but fail to meet the needs of the majority of those with hearing loss.

Some implantable devices stimulate the temporal bone directly.

Others vibrate the ossicular chain through various means such as a piP7,.Pl~tric device or a magnet attached to one of the ossicles.

Presently-available implantable devices include those described by 20 Mahoney (U.S.

Patents 3,346,704 and 3,557,775), Branch (IJ.S.

Patent 3,764,748), Hough (4,606,329), and PCT Application WO 89/05559.

Implantable devices have been somewhat successful in ov~ fillg problems such as acoustic feedback, but frequently require high power inputs.

In addition, some implantable devices interrupt the norma] WO 95/17078 217 8 i~ ~ 4 ` i iPCT/US94114674 hearing pathway by occluding the external auditory canal or interrupting the ossicular chain.

A number of problems are associated with present]y-available hearing aids.

In-the-ear or in-the-canal hearing aids block the external auditory canal and interfere with the user's remaining natural hearing, creating what is generally known as the "occlusion effect." These devices alter the acoustical characteristics of the auditory canal and often reduce the normal 8-10 dB amplifying effect of the concha (the centra] convexity of the external ear).

Normal conductive hearing is decreased while bone conduction hearing is enhanced by approximately 9 dB, adversely affecting the user's perception of his own voice.

This in turn may result in abnormal voice modulation.

In addition, the amplified sound is frequently perceived as harsh and unpleasant due to a different frequency distribution from natural sound.

Children, the elderly and the hi~nrli~rped may have difficulty with the tiny and/or complicated controls of some in-the-ear hearing aids, due to illllll~Ulily, lack of sufficient manual dexterity to manipulate the controls, or lack of sufficient ability to learn new skills.

Such users are more successful in manipulating the controls of behind-the-ear aids.

Many users experience problems with acoustic feedback and background noise.

Feedback is most evident in highly-mini~t--ri7Pd devices, an unavoidable consequence of the decreased distance from the speaker to the microphone.

Poor signal-to-noise ratios result from the fact that hearing aids amplify signals in~icrriminilr~ly, thus, amplified background noise may prevent a user from hearing and understanding the WO 9~/17078 217 8 7 5 ~ ~ ~` PCT/US941146~4 0 signal he or she wants to hear.

By way of example, it may be difficult to ~iictin~llich a c~l~vcl~dlion from the background noise at a noisy cocktail party.

Of necessity, in-the-ear hearing aids are placed in the portion of the 5 auditory canal that produces cerumen (ear wax), blocking the normal egress of cerumen, forcing it inwardly where it blocks the auditory canal as well as the vent and speaker ports of the aid.

In addition, occlusion of the canal prevents the normal circulation of air, creating a "stuffy" sensation and predisposing the user to external ear infections.

Some users 10 develop an allergic response or intolerance when using an in-the-ear hearing aid constantly.

Venting the device may partially overcome the occlusion effect, but may cause ,ulublcllldlic acoustic feedback.

(~An~litlAt~s for hearing aids may refuse binaural fitting because of the cost or the occlusion effect.

As a result, they have an imhAlAnr~ in 15 hearing from ear to ear, which results in difficulty with directional hearing.

Devices that aim to provide directional hearing are available.

For example, Davis (U.S.

Patent 5,239,588) mounts a stereophonic microphone on top of the user's head.

Amplifiers are connected imm~ ^ly adjacent to the microphone and subcutaneous wires connect 20 the amplifiers to electroacoustic transducers in the ear canals.

Some users complain of discomfort when wearing a hearing aid, and many refuse to use one because of its association with aging or infirmity.

When others notice that a person is wearing a hearing aid, they often speak in an abno~ally loud voice which leads to discomfort.

WO 95/1707~ 217 ~ ~ 5 4 pcT~us94n467~ s The less noticeable a hearing aid is to others, the more acceptable it is to its user.

Over the years, the si~e of hearing aids has ~limini~h!~d and their general quality has improved.

However, there has been little ci~nific~nt S i~ OV~ IIt in hearing aid technology.

Even the digitally programmable hearing aid, which offers the user some previouslyunavailable flexibility in the frequency distribution of the amplified sound, does not represent a revolutionary change.

Presently-available hearing aids do not satisfy the need of many potential users for an 10 inconspicuous, easy-to-use device that provides adequate sound amplification with low acoustic feedback.

Overall, only about 10% of those who might benefit from a hearing aid actually use one Thus, a ~i~nifi~.~nt problem remains in helping those with hearing imr~irm~nt Perhaps the single most illl~)UI ~ incentive to increased hearing aid use 15 would be an aid with an improved signal-to-noise ratio that uses rather than replaces the user's remaining natural hearing.

SUMMARY OF THE INVENTION According to its major aspects and broadly stated, the present invention is a hearing aid having a microphone, an electronics package c~nt:~inin~ a sound amplifier and a power source, and an implantable speaker or sound cQn~ t--r.

The microphone is positioned in the conchal bowl of the user, and the electronics package is placed behind the pinna, connected to the microphone via a small hole formed in the concha.

The WO 95/17078 217 8 ~ ~ ~ PCT/US94/1467 1 0 : , ' ~ !

sound conductor is p~ all~ ly installed in the external auditory canal region, ~ n-lin~ from the housing behind the ear through the soft tissue of the external auditory canal and into the auditory canal medial to the cerumen-producing portion of the canal.

The outer end of the sound 5 conductor is connected to the electronics package; the inner end is positioned medial to the cerumen-producing portion of the auditory canal for directing amplified sound towards the ear drum.

Using sound from the anterior side of the pinna for amplification and delivery to the ear drum without blocking the auditory canal is a 10 major feature of the present invention.

This arrangement enables the quality of the sound received by the wearer, whether amplified by the present device or received directly through the auditory canal, to be more like what the wearer P-trPri~nred before hearing loss.

An i~ o~L~ feature of the present invention is the arrangement of 15 the implantable sound conductor for delivery of amplified sound to the ear drum.

The major portion of the auditory canal is by-passed, leaving it free to function in its normal manner.

The inner end of the sound c~nrlllctor is positioned in the inner portion of the auditor~v canal, medial to the cerumen-producing portion of the canal and close to the outer 20 surface of the ear drum so that amplified sound is aimed directly at the ear drum.

The sound conductor protrudes only a small distance into the auditory canal, preferably no more than d~l!lU~ ly I mm, to avoid or~ in~ the auditory canal and to preserve the user's natural hearing.

All~ /ely, the sound conductor bypasses the ear drum to direct 25 amplified sound at the round window of the middle ear.

WO 9S/17078 2 1 7 ~ 7 ~ 4 PCT/US9411467.1 Anothe} feature of the present invention is the placement of the microphone and the electronics package.

The microphone and electronics package are worn in the manner of a "reverse earring," with the electronics package concealed by the external ear and the user's hair and 5 the microphone penetrating through the pinna to receive sound from the front of the pinna, as the user would normally.

Placement of the microphone in the concha] bowl not only exploits the natu}al soundcollecting properties of the external ear and provides protection from wind noise, but also renders the microphone inconspicuous when installed 10 for use.

Like the sound conductor, the microphone is positioned so that the user's natural hearing is not blocked but can augment the sound of the present system.

Still another feature of the present invention is the method for installing the hearing aid, involving surgery that can be performed under 15 local :~nP.cth~ci~ on an out-patient basis.

The sound conductor, in the form of a length of flexible tubing, is implanted in the soft tissues of the external auditory canal region, preferably behind the auditory canal with an outer end extending outwards from the posterior surface of the ear and an inner end communicating with the non-cerumen-producing 20 portion of the auditory canal. A small hole is formed through the concha, and, after the hole heals, the microphone is connected to the amplifier input by a stem that passes through the hole.

The sound con~ ct~r is connected to the receiver output.

The non-implanted portion of the hearing aid -- the microphone and the electrorlics -- may be 2~ removed during sleeping, showering, and so forth simply by WO 95/17078 21~ 8 ~ ~ ~ PCT/US94/14674 1~ ~ i- ` f ` ` 8 ~iicConnrCtin~ the electronics package and the microphone from the sound conductor.

Other features and advantages of the present invention will be apparent to those skilled in the art from a careful reading of the Detailed 5 Description of a Preferred Embodiment presented below and accompanied by the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, Fig. I shows a side view of the ear of a user, with a hearing aid according to a preferred embodiment of the present invention installed for use;

Fig. 2 is a horizontal cross-sectional view along line 2-2 of Fig. 1, 15 showing a microphone and electronics package according to the invention;

Fig. 3 is a horizontal cross-sectional view along line 3-3 of Fig. 1, showing the placement of the sound conductor;

Fig. 4 is a perspective view showing the a~rangement of the 20 microphone, electronics package and sound conductor;

Fig. 5 shows a sound conductor according to another preferred embodiment of the present invention; and Figs. 6A and 6B shows a sound conductor according to still another preferred embodiment of the present invention.

WO 95/17078 217 8 7 ~ 4 PCT/US94114674 DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT In the following description, similar structural elements, portions or surfaces are referred to by the same reference numerals in order to simplify the understanding of the seq~ nfi~l aspect of the drawings.

The terms "proximal," "distal," "anterior," "posterior," "medial," "lateral, " "inner" and "outer" are used in the customary anatomical sense.

The problems of acoustic feedback, occlusion of the auditory canal, low signal-to-noise ratio and cosmesis are addressed by a hearing aid that 10 includes a microphone, an electronics package, and a sound conductor.

The microphone is worn preferably in the superior portion of the conchal bowl, and a housing containing the electronics package is worn behind the ear and connected to the microphone via a small hole in the conchal cartilage.

When implanted in the user, the sound conductor bypasses the 15 cerumen-producing portion of the external auditory canal and directs amplified sound towards the inner ear.

The device augments the user's remaining natural hearing without blocking the external auditory canal.

Referring now to Fig. 1, there is shown a side view of the ear of a user, with a hearing aid according to a preferred embodiment of the 20 present invention installed in the ear.

An external ear 10 includes a pinna 12, and a conchal bowl 14 with an upper or superior portion 16 and a lower portion 18.

An auditory canal 20 leads from conchal bowl 14 to an - ear drum and middle ear (not shown).

Canal 20 and surrounding soft tissues 22 constitute an external auditory canal region 24 (Fig. 2). A 25 hearing aid 30 includes a microphone 32 worn in superior portion 16.

WO 9S/17078 2 ~ ~ 8 7 ~ 4 PCT/US94114674 As best seen in Fig. 2, microphone 32 is attached to ear 10 via a hole 34 formed through pinna 12.

An electronics package 36 is placed against a posterior surface 38 of ear 10, directly behind superior portion 16 of conchal bowl 14.

Electronics package 36 contains an amplifier, a S battery for energizing the package, a receiver, user-operable controls, and other electronics needed for the operation of aid 30. I)epending on the patient and his hearing loss, package 36 may include other electronics such as cu~ ,asion circuitry or noise reduction circuitry.

Microphone 32 is positioned near an anterior surface 40 of ear 10, attached to 10 electronics package 36 by a stem 42.

Stem 42 contains electrical wiring (not shown) for electrically connecting microphone 32 and package 36.

A sound conductor 50 extends from package 36 through tissues 22 of external auditory canal region 24, generally as shown in Fig. 3.

Sound conductor 50 has an outer, input end 54 c~ d to an output of 15 package 36, and an inner, output end 56 that presents amplified sound close to the outer surface 58 of the user's ear drum.

Auditory canal 20 has a lateral, cerumen-producing region 26, and a medial, non-cerumen-producing region 28.

Sound conductor 50 extends past region 26, bypassing region 26, and directs amplified sound 20 medially towards the eardrum.

Output end 56 extends through the skin layer 21 of canal 20, communicating with canal 20 in medial region 28.

End 56 is positioned so as not to occlude canal 20 and to direct the amplified sound at ear drum 58, preferably within d~ u~illla~ely 3-9 mm of ear drum 58 ~nd more preferably within a~ lldl~ly 5-7 mm of ear ~WO 95117078 21 7 ~ 7 S ~ PCT/US94/1467.1 Il drum 58.

End 56 may have a rolled edge 62 as shown in Fig. 3, or, alternatively, a flat edge.

A female-type connector 70 is attached to outer end 54 of sound conductor 50, and a male-type connector 72 is attached to package 36.

5 Connectors 70, 72 are dimensioned so as to detachably connect package 36 to sound conductor 50.

Alternatively, connector 70 may be a maletype connector, and connector 72 a female-type connector.

A view of hearing aid 30 installed for use is shown in Fig. 4.

Electronics package 36 is positioned behind ear 10, connected to 10 microphone 32 and sound conductor 50 generally as indicated.

Microphone 32 collects sound waves that impinge on conchal bowl 14 and transmits an output signal to package 36, where the signal is amplified, modified, and directed to ear drum 58 by sound conductor 50.

Microphone 32 is positioned in superior portion 16 of conchal bowl 14, 15 and inner end 56 of sound conductor 50 extends only a small distance into auditory canal 20 (preferably no more than d~ U~ ldl~ly 1-2 mm).

Thus, canal 20 is not occluded by either microphone 32 or sound conductor 50.

Rather than rliminichin~ the user's remaining natural hearing as occurs with devices that occlude the auditory canal, hearing aid 20 30 enhances hearing by adding amplified sound to the user's natural hearing.

Hearing aid 30 is installed generally as follows:

- 1.

The region posterior to auditory canal 20 and superior portion 16 of conchal bowl 14 is ~nf~cth~ti7~-1, preferably by a local anesthetic.

25 This region is readily anesthetized by many types of local ~nPSthPti~`C WO 9~/17078 21~ 8 ~ 5 4 12 PCr/USs4~l4674 however, other types of ~nPsthf~si~ or analgesia may be useful for some users.

2. A first incision is made through the skin of posterior surface 38 of pinna 12, at the location where it is desired to install microphone 32 5 and electronics package 36 (see Figs. 2, 4). A small hole (hole 34) is formed through the cartilage of superior portion 16 and the skin of anterior surface 40, preferably by punching through the conchal cartilage with a suitable punching tool and incising the anterior skin with a scalpel.

Hole 34 is preferably between approximately 1-3 mm in diameter, 10 although sizes outside this range may also be useful.

Most preferably, hole 34 is approximately 2 mm in diameter.

3. A stent or some other suitable type of retainer is placed in the hole to prevent closure during the healing process.

The stent is rotated by the user at intervals, preferably several times daily, to prevent 15 adhesion to the skin and cartilage and facilitate formation of a prl Ill,.

skin-lined hole 34.

During healing, the area is cleaned regularly with water, alcohol, hydrogen peroxide solution or the like.

4. A second incision is made through the skin of posterior surface 38, at the desired location of outer end 54 of sound conductor 50 (Figs. 3, 20 4). A trochar or other suitable device is advanced through the skin and soft tissues 22 behind auditory canal 20, and guided through the tissues until it p~ L~ canal 20 at the desired position of irmer end 56 of conflllctrr 50.

One end of a length of flexible tubirlg is attached to the trochar.

The trochar is then drawn back from canal 20 until the tubing 25 extends through tissues 22, with inner end 56 in approximately the WO 95/17078 2 :~ 7 ~ 7 5 4 PCT/US94/14674 1~ position shown in Fig. 3 and an opposing end l~x~Pn~lin~ outwards from posterior surface 38.

Conductor 50 is cut to length, and connector 70 is attached to outer end 54.

Inner end 56 of sound conductor 50 is positioned in non-cerumen5 producing region 28, medial to cerumen-producing region 26.

Region 28 is normally sterile, thus, end 56 requires no special care after installation.

Outer end 54 is rinsed at intervals with water, alcohol, hydrogen peroxide solution or the like, preferably at least once per day, while healing.

5.

The electronics needed for operation of hearing aid 30, including an amplifier, receiver, power source, controls, and the like, are encased in a custom mold (electronics package 36) to fit snugly against posterior surface 38 of the user's ear, and pcl"lallelllly attached to microphone 32 via stem 42.

6.

After hole 34 heals, sound conductor 50 is connected to electronics package 36 and microphone 32 is inserted into hole 34.

The controls of hearing aid 30 are preferably located on the surface of package 36 so as to be readily accessible by the user.

When aid 30 is installed for use and energized, amplified sound is 20 p}esented close to ear drum 58, preferably within à~lO~ ]y 3-9 mm of the ear drum.

Due to the placement of microphone 32 in conchal bowl 14, the inherent sound collecting and amplifying properties of external ear 10 are substantially unaltered by the presence of the microphone.

Neither microphone 32 nor sound conductor 50 occludes auditory canal 25 20, thus, the normal conduction of sound through canal 20 is not WO 9~/17078 217 8 7 5 ~ PCTIUS94/14674 1~ 14 -. . .

dlsturbed.

As a result, hearlng ald 30 IS both "acoushcally hransparent" and "subjectively lldllsl~alt;llt," that is, it augments the user's remaining natural hearing rather than replacing all or part of that hearing by amplified sound.

To the extent of his or her remaining natural hearing, S the user receives the full harmonic range of natural sound as well as amplified sound from aid 30, and is therefore less likely to perceive the amplified sound as being abnormal or unpleasant.

Microphone 32 and electronics package 36 may be removed from the user's ear when not in use, such as while sleeping, showering, 10 swimrning, and so forth.

Those components of aid 30 which contact the skin or soft hssues of the user are preferably made of biocompatible m~t~ri~lcl as will be explained below.

However, any hssue reaction in the vicinity of hole 34 may be controlled by temporarily removing microphone 32 and package 36 whenever that area is irritated Ol infected.

15 The occurrence of such reactions is Ill;llilll;,r.d by rinsing hole 34 at regular intervals, preferably a~ v,.illlal~ly once per day, with water, alcohol, hydrogen peroxide solution, or some other mild ~ inf~-ct~nt Implantable sound conductor 50 takes the forrn of a length of flexible tubing having an outer diameter between al~Jlu~dlllalely 1-3 mm, 20 preferably a diameter of ~IJIu~illla~ly 2 mm.

Conductor 50 is sufficiently flexible for installation in hssues 22 of exter~al auditory canal region 24, and is sllhst:~nti~lly illly~ ~lible to the user after installahion.

Conductor S0 may be installed as shown in Fig. 3, or, all~lllali\~t;ly, installed in some other suitable posihon in region 24.

WO9~i/17078 ~ 37~4 PCT/US91/1467~ Sound conducto} 50 may assume other forms without departing from the spirit of the present invention.

If desired, conductor 50 may be a closed tube 74 that extends from electronics package 36 (Fig. 2) eo a middle ear 76, medial to ear drum 58 (Fig. 5).

Tube 74 has an inner end 78 that abuts the round window 80 of middle ear 76, thus, end 78 is preferably rounded and sufficiently flexible to conform to the shape of window 80.

Tube 74 transmits sound from electronics package 36 directly to window 80.

For efficient sound transmission, tube 74 is preferably fil]ed with a biocompatible fluid such as physiological saline solution.

Alternatively, a lens 90, including a ",r".l"A"P 92 and a magnet 94, may be carried by ear drum 58 (Figs. 6A and 6B).

An electromagnetic driver 96 is installed in tissues 22 of external auditory canal region 24, preferably medial to cerumen-producing region 26 and positioned within ~I~IuAi~l~ately 2-10 mm of ear drum 58.

Electromagnetic driver 96 is connected to electronics package 36 by an insulated wire 98.

Electromagnetic driver 96 transmits an electromagnetic signal to lens 90.

Magnet 94 is any suitable type of p~lllldlll~ magnet, such as a S~mArillm cobalt magnet encased in silastic or similar biocompatible material.

As shown in Figs. 3 and 4, conductor 50 has an a~loAillldL~ly constant diameter throughout its length, however, a variable-diameter sound con-lllctnr may be used. A variable-diameter sound conductor for use with the invention might be, for example, a "Libby tube" having a diameter that increases gradually from outer end 54 to inner end 56.

Use of a Libby tube for conductor 50 increases the high-freqoency output of WO95/1707~ 217 8 ~ S 4 PCT/US94114674 16 the conductor due to enhanced conduction of high frequencies by such tubing, thereby increasing the perceived "natural" quality of the amplified sound.

However, any loss of natural high frequency harmonics due to use of a constant-diameter sound conductor can readily be comrçnc~f.od for 5 by suitably-programmed electronics in package 36. _ Conductors 50 and 74 are made of a biocompatible material that is well tolerated by body tissues.

Suitable materials include GORE-TEXTM, silicon rubber compositions such as SILASTICTM, and GORE-TEXTMcoated SILASTICTM.

Polytetrafluoroethylene tubing (PTFE, TEFLONTM) 10 and PARYLENETM tubing may also be used.

These materials are well tolerated by most users, with almost no foreign body reactions.

However, flexible tubing made of other biocompatible materials may also be useful.

Wire 98 and amplifier 96, if present, are covered by biocompatible materials such as those listed above.

The material of conductors 50 and 74 may be i~ -dl~d with silver to help reduce the incidence of infections.

Similarly, wire 98 and amplifier 96 may be covered by a silver-ill-~ dL~;d material.

Alternatively, con-lllctors 50 and 74 may be provided with silYerilll~-~,E,lldl~d outer coatings or cuffs at the junctions of ends 54 and 56 20 with the skin.

Inner end 56 of conductor 50 is positioned in a normallysterile portion of auditory canal 20, away from the active glandular (i.e., cerumen-producing) portion of the external auditory canal, so the possibility of infection is Illillilll;~r(l Any infections that occur may be treated with local care (irrigation with mild di~ r~ such as alcohol 25 and hydrogen peroxide; application of topical antibiotics).

If desired, WO 95/1707~ 2 1 7 8 7 5 4 PCT/IIS94/14674 17 disinfectants and topical antibiotics may be injected into conductor 50 for delivery to region 28 of auditory canal 20.

Conductor 50 may be removed if necessary, and replaced after the infection clears.

Microphone 32 is preferably an omnidirectional microphone, S oriented facing approximately forwards to take advantage of the natural sound-collecting properties of ear 10.

While an omnidirectional microphone is preferred, other types of microphones including directional microphones may also be useful.

The optimum type of microphone for hearing aid 30 depends on such factors as the size of the 10 microphone, its precise position in the user's concha, and the components of electronics package 36.

The external ear is a natural parabolic sound collector from the front, and superior portion 16 of conchal bowl 14 is well shadowed and protected from wind and wind noise.

The signal-tonoise ratio of hearing aid 30 is increased by placing microphone 32 in the 15 natural sound collector of the concha and by avoiding occlusion of external auditory canal 20.

As noted above, increased signal-to-noise ratios are crucial to und~ an.:lillg speech in a noisy t;llVilUIIIIII::III.

The signal-to-noise ratio of aid 30 may be as much as 15 dB higher than that of canal-occluding aids.

For those users who need binaural amplification, 20 use of an aid 30 in each ear results in further illl~)lUVt;lllt;llt:j in the signal to-noise ratio.

Microphone 32 may extend above anterior surface 40, preferably by no more than 1-3 mm.

All~lllaliv~ly7 microphone 32 may be approximately flush with surface 40.

Microphone 32 may be flesh25 colored to enhance its inconspicuousness.

However, some users may WO 95/17078 217 8 ~ ~ ~ PCT/US94114674 18 prefer a microphone 32 having a decorative appearance similar to a smallearring. ~ ~ Microphone 32 and elèctronics package 36 are removably attached to the user's ear.

Microphone 32 may be p~rrn~n~n~ly attached to stem 5 42, or may be detachable from stem 42 and package 36.

By way of example, stem 42 may have a diameter d~ ldl~]y equal to the diameter of hole 34, but preferably slightly larger than the diameter of the hole.

Stem 42 may also carry a collar 64 (Fig. 2).

The user installs microphone 32 in conchal bowl 14 by gently pushing the microphone into 10 hole 34 from the rear.

Stem 42 is held in place by collar 64 and by friction between the stem and the skin lining hole 34.

In addition, the underlying cartilage has some tensile strength and can "grip" stem 42.

Microphone 32 is removed by grasping package 36 and gently pulling backwards.

Microphone 32 and package 36 are configured as a "reverse earring," with rnic}ophone 32 pushed onto stem 42 after the stem is installed in hole 34.

Alternatively, microphone 32 may be attached to stem 42, so that stem 42 is inserted into hole 34 from the front for connection to a suitable input connector (not shown) on package 36.

20 Since stem 42 is dimensioned to fit in hole 34, the length of stem 42 is approximately equal to the thickness of the cartilage at the location of hole 34.

If desired, the outer surface of microphone 32 rnay be ~ illld~ly flush with anterior surface 40 except for a flange to help retain the microphone in position.

As will be evident, other methods for 2~ installing microphone 32 and package 36 may be used without departing WO 95/17078 2 1 7 8 7 S ~ PCT/U594/1467~ 19 from the spirit of the present invention.

By way of example, the anterior skin over hole 34 may be left intact when the hole is formed.

Then, stem 42 and microphone 32 are simply pushed into hole 34 from the rear, held in place by the natural tensile strength of the conchal cartilage. A tube or 5 stent may be pc~ ld~ t]y implanted in hole 34 to serve as a guide and retainer for stem 42.

Stem 42 is preferably s--hst~n~i~lly rigid in order to facilitate insertion into hole 34 (and removal from hole 34), and hollow to accommodate electrical connections between mucrophone 32 and 10 electronics 36.

Stem 42 is made of a biocompatible material, including but not limited to stainless steel, gold, gold-plated metal, and ceramic.

Stem 42 may coated with a material such as silicone rubber or polytetrafluoroethylene .

Electronics package 36 may contain an amplifier that is responsive 15 to the output signal of microphone 32, a battery, user-operable controls, frequency-culll~ dLion circuitry, a receiver, and such other electronics as are needed for operation of hearing aid 30.

These parts may be selected from any readily-available, conventional colll~,ol~ that are suitable for use with microphone 32 and sound conductor 50.

20 Electromagnetic driver 96, if present, is any suitable type of electromagnetic driver that can be implanted in tissues 22.

The CUIII~JOI~CII~ of hearing aid 30 may be selected for each particular user's - individual needs.

Thus, users with severe hearing loss may benefit from a more powerful amplifier than those with relatively mild hearing loss, W0 95/17078 2 1~ ~ 7 ~ ~ PCTIUS94/1467 J O ; ! . ~ 1 20 and music lovers may benefit from an amplifier with adjustable frequency ranges.

Package 36 is encased in a substantially water-impervious outer housing, preferably individually molded to fit behind the user's ear and 5 conform to the shape of the ear and the head.

Stem 42 is positioned so that, when package 36 is installed for use, the stem is directly insertable into hole 34 with attached microphone 32.

Package 36 is dimensioned to fit comfortably behind the ear. no greater than ~~ ldl~ly 2 cm long x I cm in diameter.

It will be evident that the size and weight of package 10 36 depends on the choice of amplifier, power supply, and so forth that are selected for aid 30.

Preferably, package 36 weighs less than ~IJIu~illld~ely 28 g (about I ounce), and more preferably less than a~ o~illldl~ly 14 g (about 1/2 ounce).

When installed for use, package 36 is attached to the user's ear at 15 two points: by stem 42 and microphone 32 at hole 34, and by connectors 70, 72 at outer end 54 of sound conductor 50.

Package 36 is supported by microphone 32, in a manner similar to a pierced earring held by an earring stud.

Connection to end 54 stabilizes package 36, adding to the user's comfort and providing additional support.

Therefore, to minimize 20 strain on implânted conductor 50, stem 42 and connector 72 are preferably approximately the same distance apart as hole 34 and outer end 54.

Because conductor 50 delivers sound to the region of ear drum 58, and microphone 32 is placed in the relatively distant location of conchal bowl 14, the problem of feedback is greatly reduced.

Feedback 25 is also reduced when a sound conductor such as conductor 74 is used, WO 95117078 2 1 7 8 7 5 4 ~ PCT/US9411467 1 21 since amplified sound is delivered in a relatively distant location from microphone 32.

Since only the sound conductor of hearing aid 30 is pPrrn~n~-ntly implanted, the need to remove a failed portion of the device is minimized.

5 Those portions of hearing aid 30 that are most likely to need replacement or "".;"lP~,,.,re -- microphone 32 and electronics package 36 -- are not implanted and therefore are readily available for ,llAllllr",ll.re as needed.

By providing a sound conductor that bypasses cerumen-producing region 26 of the external auditory canal, a hearing aid 30 according to the 10 present invention avoids the predisposition to external otitis caused by in the-ear hearing aids.

In addition, the cosmetic appearance of aid 30 is improved over that of many currently-available hearing aids.

Electronics package 36, containing a battery, amplifier, and so forth, is placed behind the ear, where it is concealed by the ear and the user's hair.

Only 15 microphone 32 shows in superior portion 16 of conchal bowl 14.

User operable controls on package 36 may be made simply to minimi~e difficulty in manipulating the controls.

Other problems experienced by users of presently-available devices are avoided, including ear canal occlusion, secondary abnormal sensation 20 and the abnormal quality of amplified sound.

Discomfort is avoided because the external ear is a relatively soft and compliant site for the placc~ of a hearing device.

Once installed, hearing aid 30 is no more perceptible by the user than is an earring.

The power needs of aid 30 are reduced since the amplified sound is presented close to the user's ear 25 drum.

Reduced feedback achieved by the separation of sound conductor WO 95/17078 PCT/US94114674 22 SO and microphone 32 enables greater amplification without the lirnitation of feedback.

Finally, the sound comes from the portion of the ear that is used for collecting sound but without the usual ear canal blockage, so the quality of sound that is received by the wearer, from the 5 present invention and directly from the ear canal, is more like that the wearer enjoyed before his or her hearing became impaired.

It will be apparent to those skilled in the art that many changes and substitutions can be made to the preferred embodiment herein described without departing from the spirit and scope of the present invention as 10 deflned by the appended claims.