US3102172A

US3102172A - Hearing aid

Info

Publication number: US3102172A
Application number: US852441A
Authority: US
Inventors: Cohen Michael
Original assignee: ARDENTE ACOUSTIC LAB Ltd
Current assignee: ARDENTE ACOUSTIC LAB Ltd; ARDENTE ACOUSTIC LABORATORIES Ltd
Priority date: 1958-11-12
Filing date: 1959-11-12
Publication date: 1963-08-27
Anticipated expiration: 1980-08-27

Description

Aug. 27, 1963 M. COHEN HEARING AID Filed Nov. 12, 1959 4 Sheets-Sheet 1 FIG! M. COHEN Aug. 27, 1963 HEARING AID 4 Sheets-Sheet 2 Filed Nov. 12, 1959 M. COHEN Aug. 27, 1963 HEARING AID 4 Sheets-Sheet 5 Filed Nov. 12, 1959 9 M. COHEN 3,102,172

I HEARING AID Filed Nov. 12 1959 4 Sheets-Sheet 4 70 ll/I12 I FIG.23

. between the receiver and the casing wall. that the casing must be undesirably larger in order to accommodate the foamed plastic'or rubber parts. In spite company of Great Britain I I Filed Nov. 12, 1959,'Ser. No, 852,441

United sate, Patent tions between the amplifier and the microphone and receiver, said connections including flexible conductors extending through said block between the first and second Claims priority, application Great Britain Nov; 12, 1958 19 Claims. (Cl. 179-107) This invention relates to hearing aids' to be worn on the head. p I

It isknown to provide hearing aids which are incorporated in spectacles frames orare worn in the ear, behind the ear or inthe hair. Such hearing aids consist prin- 'cipally of amicrophone to receive the sounds and to produce electrical signals accordingly, a transistor amplifier to amplify the electrical signals and a receiverto produce sounds from the amplified electrical signals. The volume f of the sound emitted by the receiver can be regulated by avolume control which adjusts the gain of the amplifier.

1A flexible tube usually extends from the receiver into the auditory canal of the wearer and is sealed therein by a plug having a passage therethrough forthe flexible tube. The plug is moulded to be a good fit in the car ot the wearer, since, in addition to supporting the tube comforta- :bly in the ear, its purpose is to prevent sound wavescoming out of the ear, from the inner end of the flexible tube,

' arid influencing the microphone. Influencing of the microphone by sounds emanatingfrom the. earphone is known I as acoustic feedback and produces whistling noises. Disturbing noises will also be produced if mechanical vibrations of the receiver are transmitted-to the microphone,

, this being known as mechanical feedback.

Hearing aids of the kind described above have to be i very small and it is common practice to mount the micro-.

phone, the amplifier and the receiver in a common casing.

However, inherent. in this construction are particularly serious problemsof acoustic and mechanical feedback.

- Mechanical vibrations from the receiver are transmitted to the microphoneby way of components'fitted on the inside walls of the casing and also by way of the casing walls themselves. Moreover, a proportion of the sound emitted by the receiver travels within the casing to the microphone. Attempts have been made to solve the problemof mechanical feedback by resiliently mounting the microphone and the receiver within the casing, for example by interposing pads of foamed rubber or foamed plastic between the microphone and the casing wall and This means of all known precautions to limit acoustic and mechanical feedback, in view of their existence it is necessary to limit the gain of the hearing aids to about 40 db.

- According to the invention there is provided a hearing aid of the air conduction type comprising a casing assem [blyincluding a first substantially rigid casing means in @cluding a microphone, a second substantially rigid casing means including a receiver, and coupling means coupling means. comprising a .compl-iable block disposed between said first and second casing means to retain said first and second casing means, wholly out of rigid contact but in r such a close proximity that saidcasing assembly is sub-' stantially rigid as a whole, said blockserving to resist mechanical feedback from one casing to the other, an

amplifier in said casing assembly and electrical connechow the same may be carried into effect, reference will now be made to the accompanying drawings in which:

FIGURE 1 is a side view, and FIGURE 2 is a top plan view, of a complete hearing aid to be worn behind the ear,

FIGURE 3 is a side view, corresponding to FIGURE 1,

showing the inside of part of a casing of the hearing aid.

FIGURE 4 is a top plan view of that casing part,

FIGURES 5 and 6 are views of the casing part, as seen in the directions of the arrows Y and Z, respectively, in FIGURE 3,

JFIGURE 7 is a sectional view of the casing part, as seen inthe direction of the arrows VII-VII in FIG- URE 3,

FIGURE 8 is a side view showing the inside of a cover which is combined with the casing part shown in FIG- URES} to 7 to form a casing,

FIGURE 9 is a top plan view of the cover,

FIGURE '10 is a side view of a holder for an electric cell,

.FIGURE 11 is a sectional view of the holder, as seen in the direction of the arrows XI-XI in FIGURE 10 the hear-inga'id of FIGURE 24,

and showing the cell in position,

FIGURE 12 shows the inside of another casing,

FIGURE 13 is a sectional view of the latter casing, as

seen in the direction of the arrows-XIIIXIII in FIG- URE l2, and showingalso a microphone and associated circuit elements,

FIGURE 14 is aside view of the casing of FIGURES 3 to 9,.with the cover removed, showing the components that are fitted therein,

FIGURE 15 illustrates a first member that is used to connect the two casings together, I

, FIGURE 16 is a further view of that member, as seen in the direction of the arrow XVI in FIGURE 15,

FIGURE 17 illustrates a second member that is used to connect the two casings together, FIGURE 18 is a further view of the second member, as seen in the direction of the arrow XVIII in-FIG- URE l7,

FIGURE 19 is a perspective view of the first and second members after assembly with foamed rubber pads,

FIGURE 20 is a plan view of a contact plate, FIGURE 2 is a side view of the contact plate,

FIGURE 22 is a pictorial view of an alternative form of the casing of FIGURES l2 and 13, p

FIGURE 23 is a sectional view, taken as indicated by the arrows XXIII in FIGURE 22, of a portion of the casing shown in FIGURE 22,

7 FIGURE 24 is a diagrammatic view of a part of a hearing aid of the spectacles type,

FIGURE 25 illustrates a couplingstructure for use in FIGURE 26 is a diagrammatic view of a hearing aid to be worn behind the ear or in the air, and

FIGURE 27 shows diagrammatically a hearing aid to be worn in the ear.

The hearing aid shown in FIGURES 1 to 21 consists oftwo casings 1 and 2 made of cellulose propionate, electrical components within the casings, a tube 3 extending from'the casing 1 and a plug 4 which is to be inserted into the auditory canal. When the hearing aid is in use, the casings 1 and 2 will be positioned between the pinna and the side of the head and towards the back of the pinna so that a person looking at the wearer from the front will be unable to see much, if any, of the casings 1 and 2. The casing 2. will be at the back end, and at the same time the lower end, of the structure.

The casing 1 consists of a base part 5 and a cover 6 therefor. The base part has a fiat, arcuate bottom panel 7 and two

side walls

8 and 9 extending from the edges thereof. The side Wall 8 is formed with a recess 10 which receives a knurled rotary volume-control member 11. Also formed in the side wall 8 is a shallower and longer recess 12 which receives part of a holder 13 (shown in FIGURES l0 and 11) for an electric cell. The recess 12 is deepened at 13 to accommodate the actuating arm of an on-otf and tone-control switch, which arm is shown at 14 in FIGURE 14. There are no such recesses in the side wall 9.

At the end of the base part 5 which is marked 5A in FIGURE 3 there is an end wall 15 and a nose portion 16, the latter being formed with a groove 17 which receives a connecting piece 18 (shown in FIGURE '14) for connecting the tube 3 to a receiver which is within the casing I. At the opposite end, 5B, of the base part 5, there is no end wall but only two very short inwardly-projecting portions 20 extending from the ends of the

side walls

8 and 9.

A raised portion 22 projects slightly from the inside of the bottom panel 7 and is partly surrounded by two L- shaped ridges 23A and 2313. The raised portion 22 serves as a mounting platform for the control member 11. Two ledges 25 land 26 extend along the insides of the

side walls

8 and 9 and are each formed at one end with an inwardly projecting nose, 27 or 28. The

noses

27 and 28 are formed with

holes

29 and 30 which extend through the bottom panel 7 and receive two screws (not shown) that pass from the exterior of the casing, through the

holes

29 and 30, and into internally screw-threaded ends of two metal tubes, shown at 34 and 35 in FIGURE 14.

The cover 6 has an arcuate bottom panel similar to the panel 7 of the base part 5 and it has two side walls 41 and 42-, an end wall 43 and a nose portion 44 having a groove 45, the parts 43 to 45 being similar to the parts 15 to 17 already described. The side wall 41 is formed with a recess 39 which, like the recess 12 in the casing part 5, receives part of the holder 13. Projecting from one edge of the side wall 41 is a portion 46 which fits into the recess 10 in the base part 5 and terminates adjacent the control member 11, as can be seen from FIGURE 2. There are no recesses in the side wall 42. At the ends of the side walls 4-1 and 42 there are very short inwardlyprojecting portions 47 similar to the portions 2i? shown in FIGURE 3.

Holes

48 and 49 extend through the bottom panel 40 of the cover 6 and fixing screws (not shown) extend through them and into the ends of the two

tubes

34 and 35, which ends are internally screw-threaded. Thus, the two tubes and the fixing screws hold the two par-ts of the casing 1 together.

The base part 5 is formed with further holes 50-52 to receive fixing screws and the cover 6 is formed with holes 53-55 for the same purpose. All these screw holes are countersunk on the outside of the casing. The screws which pass through the

holes

50 and 53 engage in screwthreaded holes in the connecting piece 13.. The purpose of the screw holes 51, 52, 54- and 55 will be explained subsequently.

The cell holder 13 consists of a frame member having a circular internal surface 61. The frame member also has a semi-circular inwardly-directed flange 62. The circular surface 61 defines a cavity into which is fitted a mercury cell 63 (FIGURE 11) which provides the operating voltage for the electric circuit components of the hearing aid. The cell is in the form of a thick disc. It is inserted in the holder from the side which is shown to the left in FIGURE 11 and is prevented by the flange 62 from falling out of the other side. The frame member 60 is formed with a bore 64 through which passes the tube 34, which thus affords :a pivotal connection for the cell holder and enables it to be swung into the position shown in dotted lines in FIGURE 1 to enable the cell 63 to be removed and replaced by another. When the hearing aid is in use, the cell holder will occupy a position in which the surface marked 59 lies flush with the

side walls

8 and 41.

The casing 2 is roughly in the shape of a rectangular box having no lid and having a rectangular hole. Thus it has a base portion 70 formed with a rectangular hole 71, two

major side walls

72 and 73 and two

minor side walls

74 and 75. The edges of the hole 71 are rabbeted, as shown at 76, to accommodate a bafile plate 77. A microphone in a rectangular brass housing 78 is inserted in the casing 2, the sound inlet of the microphone being adjacent the bafiie plate 77 and the hole 71. Electrical components forming all, or part of, the first stage of a transistor amplifier are attached to the microphone housing 78 and are represented by the rectangle 79.

The

side walls

72 and 73 are formed with countersunk holes 80 through which fixing screws (not shown) pass. The

walls

72 and 73 are also formed internally with rectangular recesses 82, the purpose of which will be discussed below.

Further electrical components, including second, third and fourth stages of the transistor amplifier, are assembled together and disposed in the casing I, the assembly being represented by the rectangle 83. A pad 84 of foamed rubber is attached to one side of the assembly of components.

A sheet 85 of rigid insulating material (FIGURE 14) has one edge thereof resting upon the ledge 25 and the opposite edge resting upon the ledge 26, as shown in dotted lines in FIGURE 7 so that a chamber 86 is formed between the bottom panel 7 and the sheet 85. In this chamber is disposed the on-oh. and tone-control switch. The switch has contacts deposited by a printed circuit technique on that face of the sheet 85 which is nearest the bottom panel 7 of the casing 1. The contacts are wiped by a moving contact member (not shown) that is actuated by a finger (shown at 89 but not in detail) which extends through the sheet 85 from the arm 14, the arm being in the form of a disc which is pivotally mounted at the centre by means of a rivet (the head of which is shown at 88) which passes through va hole in the arm 14. The arm 14 has a portion 87 extending out of the casing 1 so that the arm 14 may be turned by the wearer so that it occupies one of three positions shown by chain lines 21 in FIGURE 14. The rivet head 88 engages one side of the cell 63 to carry the current therefrom. The other side of the cell is engaged by a contact device as shown in FIG-

URES

20 and 2,1 in the form of thin sheet metal having a curved portion 90 which actually contacts the cell and an arm 91 formed with a recess 92 at each end. The screws (not shown) which pass through the bottom panel 40 of the cover 6 and enter the ends of the

tubes

34 and 35 also lie in these recesses 92 so that the screws hold the contact device in position. For ease of illustration, the contact plate is not shown in FIGURE 14.

A receiver 95 is disposed in a housing made of brass and the latter is wrapped in a sheet of foamed rubber (not shown) and disposed in the casing 1 at the end 5A. A short tube 101 extends from the sound outlet of the receiver to the connecting piece 18.

The casings 1 and 2 are connected together by a coupling structure which includes a first coupling member shown in FIGURES 15 and 16 and a second coupling member 1M shown in FIGURES l7 and 18, these coupling members being bent from brass sheet. The member 100 has a plate portion 102 with two arms 103 tween them in FIGURE 1.

bent in one direction from opposite ends of it and two lugs 104 bent in the opposite direction from the two sides of it, the lugs being formed 'with screw-threaded holes 105. During assembly of the coupling structure, the end portions 106 of the arms 103 will be bent inwardly as shown in dotted lines. The member 101 consists of a rectangular plate 107 having its two ends bent over to of a width substantially equal to the distance between the two lugs 104, and it is laid upon, and cemented to, the portion 102 between the lugs. This sheet is shown in FIG- URE 14 but not in FIGURE 19. The second sheet, 116, is longer and wider than the plate portion 102 and is'laid thereon, and cemented thereto, with the arms 103 piercing the sheet 116. The third sheet, 1 17, is a little longer than the width of the plate 107 but shorter than the distance between the two arms 103. Its width is a little less than the distance between the flanges 108. It is laid upon, and

cemented to, the plate 107 between the flanges 108. To

assemble the coupling structure, the sheets 1 15 and .116

are assembled, as described, with the member 100 and the sheet 1 17 is assembled with the member 101. The exposed face of the plate 107 of the member 101 is then laid upon the exposed face of the sheet 116, whereafter the ends 106 of the arms 103 are bent around the sides of the plate 107 and the ends of the sheet 117, as clearly shown in FIGURE 9. It will now be understood that the

members

100 and 101 cannot be pulled apart, although they are not in contact with one another, the only mechanical connection between them being by way of the member 100 fit into the recesses S-Z inthe casing 2 and two fixing screws pass through the holes 80 and into the holes 105 in the lugs 104-. The housing 78 is separated from the member 100 by the foamed rubber sheet 115. The sheet 115 could be of paper instead of foamed rubber.

The lugs 104 will be of such length, and will be fixed to the casing 2 atsuch positions, that the casings 1 and 2 will be spaced apart as indicated by the gap 119 shown beof the coupling structure connecting the two casings together, there is no possibility of any substantial mechanical vibrations being transmitted from one casing to the other. However, the casings l1 and 2 cannot be pulled The first, des ignated 115, is a little longer than the plate portion 102 and Due to this and tothe nature.

foamed rubber sheets 116 and 1 17. The sheets 1-15 to i further apart, due to the arms 103 being bent around the

parts

101 and 117 as described above.

The electrical connections between the circuit components will be by 'way of very flexible insulated conductors, for example consisting of a few very fine tinned copper wires twisted together and insulated with polyvinyl chloride. Enamelled fine copper conductors may be used instead. The conductors 119a passing from the circuit elements in the casing 2 to those in the casing 1 will not transmit any substantial vibrations due .to their flexibility. By virtue of the holes in the foamed rubber pads 115 to 1 17, for the passage of the conductors 1119a, being smaller than the

apertures

110 and 111 in the

members

100 and 101, and being centrally located -with,respect thereto, the insulated conductors do not come into contact with the members 100 and i101. and this helps to avoid transmission of vibrations.

tube connected at one end to the receiver, an earplug An alternative form of casing 2 is shown in FIGURES 22. and 23, wherein parts corresponding to those of the earlier figures are similarly numbered. This casing differs from that previously described in that instead of there being a hole 71 in the base 70, there is a smaller hole where the base 7 0 meets the wall 74.

Referring to FIGURE 24, one arm of a spectacles frame is formed at its rear end as a casing and in it are disposed an earphone 126, a mercury cell 127 and other circuit components, represented by blocks 124. The components are arranged in a row, so that this part of the arm 125 can be made very thin. Indeed, the only parts of the spectacles frame which need be thick or wide are those which fit behind the ear, where. they are less noticeable.

A tube 3 extends from the receiver "126 to an earplug 4. At the end of the arm 125 is disposed another casing 128 containing a microphone 129 and, if desired, the first stage of a transistor amplifier. The casing 128 may be constructed like the casing 2 described above, or as modified in accordance with FIGURES 22 and 23.

The

casings

125 and 128 are mechanically connected together and spaced apart by a coupling structure which may, if desired, be constructed in accordance with FIG- URES 15 to 19, and connected to the. casings in a manner similar to that described above. ductors (not shown) again interconnect the parts within the two casings.

An alternative coupling structure for the

casings

125 and 128 is illustrated in FIGURE 25. A rigid and hollow coupling member 140, through which pass the insulated conductors (not shown), is wrapped in a foamed rubber sheet 141 and its opposite ends are inserted in the ends of the

casings

125 and 128. The sheet 141 is cemented to the surfaces which it contacts.

In the construction according to FIGURES l to 23 or in that according to FIGURE24 the two casings could be connected together by a simple rubber link but the described arrangements appear to be preferable because they prevent the hearing aid being damaged by the casings being pulled apart.

FIGURE 26 shows a hearing aid having three separate casings 130 to 132 arranged end-to-end so as to constitute circuit components 124. Thus the coupling structure which interconnects the casings containing, respectively, the microphone and the receiver consists of the third casing and two coupling arrangements according to FIG- URES 15 to 19, or two links of rubber or the like.

Referring to FIGURE 27, a moulded plastic insert 131 which is to be fitted into the ear is bored longitudinally and is formed with a cup-shaped recess 132 at the end which is to be outermost when in use. This recess is .to receive a casing 133 which houses a receiver 126. Connected to this casing by a rubber link 134, or by a coupling structure in accordance with FIGURES 15 to 19, is another, larger, casing 135 in which is mounted the microphone 129, the mercury'cell 127 and the other electric circuit components 124.

I claim:

1. A hearing aid of the air-conduction type, comprising at least two casings, a microphone in a first of the'casings, a receiver in a second of the casings, a sound-conducting adaptedto fit into the ear of the user connected to the other end of the tube to receive sound from the receiver, means coupling the casings together to form anassembly of casings shaped to be disposed wholly on one side of the head and at least partly in the rearward part of the space between the pinna and the side of the headof the Flexible electrical conuser, said coupling means including a first rigid coupling member rigidly secured to the first casing, a second rigid coupling member rigidly secured to the second casing and a compliable block disposed between the first and second members to preclude contact between them and said coupling means holding the first and second casings apart but preventing them from being accidentally pulled further apart whilst at the same time preventing them from being pushed into contact with one another, said block serving to resist mechanical feedback from one casing to the other, an amplifier in the assembly of casings and electrical connections between the amplifier and the microphone and receiver, said connections including flexible conductors extending rough said block between the first and second casings.

2. A hearing aid according to claim 1, wherein a hattery and components of said amplifier are disposed in the first casing.

3. A hearing aid according to claim 1, wherein a battery and components of said amplifier are disposed in the second casing.

4. A hearing aid according to claim 1, wherein said amplifier is a multi-stage amplifier and components of the first stage are disposed in the first casing and the components of the remainder of the amplifier are disposed in the second casing.

5. A hearing aid according to claim 1, and further comprising portions of one of the coupling members which embrace the other coupling member, thereby preventing the two casings being pulled apart.

6. A hearing aid according to claim 5, and further comprising a first plate portion of the first coupling member disposed near the first casing, a second plate portion of the second coupling member substantially parallel to the first plate portion and disposed near the second casing, two parallel arms of the first coupling member extending from opposite edges of the first plate portion, perpendicularly thereto and towards the second casing, end portions of said arms bent around opposite edges of the second plate portion to the side thereof nearest the second casing, a first compliable block separating the two plate portions and a second compliable block separating the second plate portion from said end portions of said arms.

7. A hearing :aid according to claim 6, and furth r comprising two flanges bent over from the second plate portion at opposite ends thereof, portions of said flanges defining holes therethrough and screws in said holes fixing the second coupling member to the second casing.

8. A hearing aid according to claim 6, and further comprising two parallel lugs extending from the first plate portion, perpendicularly thereto and away from the second casing, portions of said lugs defining holes therethrough and screws in said holes fixing the first coupling member to the first casing.

9. A hearing aid according to claim 8, wherein the microphone is disposed between the lugs and separated from the first plate portion by a pad of compliable material.

10. A hearing aid according to claim 1, wherein the first casing is in the form of a lidless rectangular box having portions defining an aperture, for the entry of sound, where the base meets one of the side walls.

11. A hearing aid according to claim 1, and further comprising a battery holder in said second casing and a pivotal connection between said holder and the second casing so that the holder can be swung out of the second casing for the battery to be removed.

12. A hearing aid according to claim 11, and further comprising a tone-control device and a battery in said second casing, an actuating member of said tone-control device, a pivot pin which pivotally mounts said actuating member in the second casing, and a portion of said pivot pin which constitutes a contact engaging one pole of the battery.

13. A hearing aid according to claim 11, wherein the first and second casings form part of one arm of a pair of spectacles.

14. A hearing aid of the air-conduction type, comprising first, second and third casings, of which the second is positioned between the first and third, a microphone in the first casing, a battery and at least part of an amplifier in the second casing, a receiver in the third casing, a sound-conducting tube connected at one end to the receiver, ran earplug adapted to fit into the ear of the user connected to the other end of the tube to receive sound from the receiver, finst coupling means coupling the first and second casings together, second coupling means coupling the second and third casings together, said casings and coupling means forming an assembly shaped to be disposed wholly on one side of the head and at least partly in the rearward part of the space between the pinna and the side of the head of the user, each coupling means including a first rigid coupling member rigidly connected to one of the two casings coupled by that coupling means, a second rigid coupling member rigidly connected to the other of the two casings coupled by that coupling means and a compliable block disposed between the first and second members to preclude contact between them and said coupling means holding the first and second and also the second and third casings apart but preventing them from being accidentally pulled further apart whilst at the same time preventing them from being pushed into contact with one another, said block serving to resist mechanical feedback from one casing to the other, an amplifier in the assembly of casings and electrical connections between the amplifier and the microphone and receiver, said connections including flexible conductors extending through said block between the first and second casings and between the second and third casings.

15. A hearing aid of the air-conduction type, comprising at least two casings, a microphone in a first of the casings, a receiver in a second of the casings, a soundconducting tube connected at one end to the receiver, an earplug adapted to fit into the ear of the user connected to the rather end of the tube to receive sound from the receiver, means coupling the casings together to form an assembly of casings shaped to be disposed wholly on one side of the head and at least partly in the rearward part of the space between the pinna and the side of the head of the user, said coupling means including (a first rigid coupling portion carried by one of the first and second casings, a second rigid coupling portion carried by the other of those two casings, portions of the second coupling portion which embrace the first coupling portion and prevent the two casings being pulled apart and a compliable block disposed between the two coupling members and positively preventing contact between them, said lblock serving to resist mechanical feedback from one casing to the other, said hearing aid further comprising an amplifier in the assembly of casings and electrical connections between the amplifier and themicrophone and receiver, said connections including flexible conductors extending through said block between the first and second casings.

16. A hearing aid of the air-conduction type, comprising at least two casings, a microphone in a first of the casings, a receiver in a second of the casings, a soundconducting tube connected at one end to the receiver, an earplug adapted to fit into the ear of the user connected to the other end or" the tube to receive sound from the receiver, means coupling the casings together to form an assembly of casings shaped to be disposed wholly on one side of the head and at least partly in the rearward part of the space between the pinna and the side of the head of the user, said coupling means including a first rigid plate portion carried by one of the first and second casings, a second rigid plate portion carried by the other of those two casings and positioned substantially parallel to the first plate portion, two parallel arms extending from opposite edges of the first plate portion perpendicular thereto and towards said other casing, end portions of said arms bent around opposite edges of the second plate portion to the side thereof nearer said other casing. a first compliab'le block separating the two plate portions and a second compliable block separating the second plate portion from said end portions of said arms, said block serving to resist mechanical deedb ack from one casing to the other, said hearing aid further comprising an amplifier in the assembly of casings and electrical connections between the amplifier and the microphone and receiver, said connections including flexible conductors extending through said blocks between the first and second casings.

17. A hearing aid ct the air-conduction type, comprising at least two casings, a microphone in a first of the casings, a receiver in a second of the casings, a soundconducting tube connected at one end to the receiver, an earplug adapted to fit into the ear of the user connected to the other end of the tube to receive sound from the receiver, means coupling the casings together to form an assembly of casings shaped to be disposed wholly ion one side of the head and at least partly in the rearward part of the space between the pinna and the side of the head of the user, said coupling means including a rigid tubuliar coupling member having one and inserted in the first casing and the other end inserted in the second casing and a compliable block separating the tube from the first and second casings, to preclude contact between them and said coupling means holding the first and second casings apart but preventing them from being accidentally pulled further apart Whilst at the same time preventing them from being pushed into contact with one another, said block serving to resist mechanical feedback from one casing to the other, an amplifier in the assembly of casings and electrical connections between the amplifier and ly rigid casing means including .a microphone, a second the microphone and receiver, said connections including flexible conductors extending through said block between the first and second casings.

l8. Ahearing aid of the air conduction type comprising a casing assembly including a first substantially rigid casing means including a microphone, a second substantially rigid casing means including a receiver, and,

coupling means coupling said first and second casing means, said microphone being held by said first casing means outside of and out [of rigid contact with said second casing means, said receiver being held by said second casing means outside of and out of rigid contact with said first casing means,said coupling means comprising a compliable block disposed between said first and second casing means to retain said first and second casing means wholly out of rigid contact but in such a close substantially rigid casing means including a receiver, and coupling means coupling said first and second casing means, said microphone being held by said first casing means outside of and out of rigid contact with said second casing means, said receiver being held by said second casing means outside of and out Otf rigid contact with said first casing means, said coupling means comprising a compliable block disposed between said first and second casing means to retain said first and second casing means wholly out of rigid mechanical contact, said block serving to resist mechanical feedback from one casing to the other, an earplug fitted to said second casing means in acoustical coupling with said receiver, an amplifier in said first casing means and electrical connecticns between the amplifier and the microphone and receiver, said connections including flexible conductors extending through said block between the first and second casings.

References Cited in the file of this patent UNITED STATES PATENTS 419,962 Lane Jan. 21, 1890 2,084,761 Bradley June 22, 1937 2,587,529 R'ocksell Feb. 26, 1952 2,794,085 De Angelis May 28, 1957 2,856,466 Gustafson et al. Oct. 14, 1958 2,882,348 Erickson Apr. 14, 1959 2,909,619 Hollingswortb Oct. 20, 1959 2,915,598 Brunton Dec. 1, 1959 FOREIGN PATENTS 679,303 Great Britain Sept. 17, 1952 761,169 Great Britain Nov. 14, 1956 210,888 Australia Oct. 10, 1957 792,742 Great Britain Apr. 2, 1958 794,347 Great Britain Apr. 30, 1958 1,066,621 Germany Oct. 8, 1959

Claims

1. A HEARING AID OF THE AIR-CONDUCTION TYPE, COMPRISING AT LEAST TWO CASING, A MICROPHONE IN A FIRST OF THE CASINGS, A RECEIVER IN A SECOND OF THE CASINGS, A SOUND-CONDUCTING TUBE CONNECTED TO ONE END TO THE RECEIVER, AN EARPLUG ADAPTED TO FIT INTO THE EAR OF THE USER CONNECTED TO THE OTHER END OF THE TUBE TO RECEIVE SOUND FROM THE RECEIVER, MEANS COUPLING THE CASINGS TOGETHER TO FORM AN ASSEMBLY OF CASINGS SHAPED TO BE DISPOSED WHOLLY ON ONE SIDE OF THE HEAD AND AT LEAST PARTLY IN THE REARWARD PART OF THE SPACE BETWEEN THE PINNA AND THE SIDE OF THE HEAD OF THE USER, SAID COUPLING MEANS INCLUDING A FIRST RIGID COUPLING MEMBER RIGIDLY SECURED TO THE FIRST CASING, A SECOND RIGID COUPLING MEMBER RIGIDLY SECURED TO THE SECOND CASING AND A COMPLIABLE BLOCK DISPOSED BETWEEN THE FIRST AND SECOND MEMBERS TO PRECLUDE CONTACT BETWEEN THEM AND SAID COUPLING MEANS HOLDING THE FIRST AND SECOND CASINGS APART BUT PREVENTING THEM FORM BEING ACCIDENTALLY PULLED FURTHER APART WHILST AT THE SAME TIME PREVENTING THEM FROM BEING PUSHED INTO CONTACT WITH ONE ANOTHER, SAID BLOCK SERVING TO RESIST MECHANICAL FEEDBACK FROM ONE CASING AND THE OTHER, AN AMPLIFIER IN THE ASSEMBLY OF CASINGS AND ELECTRICAL CONNECTIONS BETWEEN THE AMPLIFIER AND THE MICROPHONE AND RECEIVER, SAID CONNECTIONS INCLUDING FLEXIBLE CONDUCTORS EXTENDING THROUGH SAID BLOCK BETWEEN THE FIRST AND SECOND CASINGS.