US3019304A

US3019304A - Electroacoustic transducers

Info

Publication number: US3019304A
Application number: US90373A
Authority: US
Inventors: Weiss Erwin
Original assignee: Beltone Hearing Aid Co
Current assignee: Beltone Hearing Aid Co
Priority date: 1961-02-20
Filing date: 1961-02-20
Publication date: 1962-01-30
Anticipated expiration: 1979-01-30

Description

Jan. 30, 1962 E. WEISS 3,019,304

ELECTROACOUSTIC TRANSDUCERS Filed Feb. 20, 1961 IN VEN TOR;

ATTORNEYS.

nite States This invention relates generally to electroacoustic transducers, and more particularly to a new and improved bone conduction type of electroacoustic transducer having advantageous use in hearing aids or the like.

While electroacoustic bone conduction receivers are known and used in present day hearing aids, such prior art receivers have not proved entirely satisfactory for a number of reasons. In the past, where bone conduction receivers have been utilized in hearing aid eyeglasses for example, it has been necessary to make certain adjustments during fitting of the eyeglasses to provide sufficient static bias pressure to maintain the receiver against the skin during dynamic excursions of the receiver. This static bias pressure-typically about ten ounces-heretofore has been provided by the compliance of the eyeglasses frame and/or the use of stiffening springs with the frame. Such bending of the temples is a difiicult adjustment achieved by much trial and error during the fitting of the hearing aid eyeglasses. In addition, there is the possibility that the static pressure will change with time to alter the intelligibility of the hearing aid output.

A further disadvantage in the use of prior art bone conduction receivers arises from the use of a flat, rigid button member which makes contact with the mastoid area. Because the rigid button member cannot conform to the mastoid contour, a limited area of high contact pressure and discomfort is created. Also, since bone conduction response is a function of the area of contact between the button member and the mastoid, there is a possibility of variability in response with time as the skin and bone tissue gradually yield under pressur to conform to the flat surface of the rigid button member.

In addition, the present day mounting of bone conduction receivers, as by means of rubber rings for example, may result in a high degree of mechanical feedback transmission at those frequencies where peak forces are developed, such as at 500 cycles and 1500 cycles. In the operation of the hearing aid rubber ring mount, the latter is severely compressed and may become quite stiff. This loss in resiliency causes vibration to be transmitted to the temple case and in accordance with certain prior art practices, such vibratory feedback is reduced by the addition of certain masses to the temple case. Thus, it is known to utilize a beryllium copper casting and a lead weight at the bone conduction receiver as well as an additional weight at the microphone to reduce the vibratory feedback in these instruments. Manifestly, this has resulted in heavy frame weights which, in turn, is a source of discomfort to the wearer of the hearing aid eyeglasses.

Accordingly, it is a general object of this invention to provide a new and improved bone conduction receiver adapted to eliminate th above-described prior art difficulties.

In particular, it is an object of this invention to provide an improved bone conduction receiver construction in which the desired static pressure is developed automatically by pre-loaded torsion suspension of the receiver to thereby eliminate any need for frame adjustment.

It is another object of this invention to provide a new and improved contact button construction for a bone conduction receiver having the ability to conform to the contour of the mastoid area upon contact to provide uniformity of response at different shaped mastoids. In addition, it is an object of this invention to provide such tet ice

an improved contact button construction having a contact area much larger than that utilized in present day constructions to provide greater wearer comfort.

It is a further object of this invention to provide a new and improved conduction receiver which utilizes torsion suspension plus highly damped vibration absorbers tuned to particular frequencies to greatly reduce the over-all weight of the receiver and the support housing within which it is mounted.

It is still another object of this invention to provide a new and improved bone conduction receiver, as above, which is adapted to be mounted in a case so as to reduce mechanical vibratory feedback coupled to the case without the use of heavy physical reaction masses and without adversely affecting the low frequency response of the receiver.

It is a still further object of this invention to provide a novel bone conduction receiver having readily adjustable means for high and low frequency response and for providing the same low frequency response as prior bone conduction receivers with the use of less physical reaction mass.

It is still another object of this invention to provide a new and improved bone conduction receiver which permits the use of smaller amplifiers, as by the elimination of the interstage transformers utilized in certain present-day hearing aid amplifier constructions.

The above and other objects are realized in accordance with the features of a specific illustrative embodiment of the invention which comprises a pair of members hinged together at one end by a resilient hinge for relative movement with respect to each other and pivotally mounted by pre-loaded torsion suspension means for movement with respect to the hearing aid case. One member is combined with a slidable mass surface for enabling ready adjustment of the low frequency response of the receiver. The other member is combined with a slidable driving rod surface for adjustment of the high frequency response of the receiver. Advantageously, a permanent magnet assembly is provided between the two members for establishing a proper DC. bias flux. A coil is wound in the form of an annulus surrounding the magnet and the bone receiver is adapted to be energized by the application of an alternating potential across the coil.

Further, in accordance with a feature of this invention, a compliant contact button is mounted on the driving rod capable, when contacting the mastoid, of conforming to the shape of the mastoid area without loss of response. As explained in greater detail hereinbelow, the compliant contact button may take the form of a. flexible pouch or pillow filled with a plurality of small particles to conform to the contour of the mastoid area upon contact. Advantageously, the pouch is adapted to be formed with a relatively large contact area to nhance wearer comfort and vibration transmissibility.

The above and further novel features which are characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and operation, together with further objects and advantages thereof, will best be understood by reference to the following description taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a perspective view of a hearing aid eyeglasses temple member embodying the bone conduction receiver of the present invention;

FIGURE 2 is a cross-sectional view of the bone conduction receiver taken substantially as shown along line 2-2 of FIGURE 1;

FIGURE 3 is a cross-sectional View of the bone conduction receiver taken substantially as shown along line 3-3 of FIGURE 1;

FIGURE 4 is an exploded view of one illustrative embodiment of the bone conduction receiver in accordance with the invention; and

FIGURE 5 illustrates the bone conduction receiver of the invention in use against the mastoid area of a hard of-hearing person.

Referring now to the drawing, and more particularly to FIGURE 1 thereof, there is shown a hearing aid eyeglasses temple member embodying the present invention. Those skilled in the art will appreciate that while the invention is not limited for use with a hearing aid eyeglasses temple member and finds many other equally advantageous uses, such a hearing aid eyeglasses temple member has been shown in this application for purposes of illustration and explanation.

Thus, as shown in FIGURE 1, the hearing aid eyeglasses temple member comprises an elongated casing, of a suitable light-weight material such as plastic or aluminum, having a hinge member 12. at one end thereof suitable for hinged connection to a hinge member in the front lens frame of the eyeglasses. The central portion of the temple member 14 may house a suitable sound pick-up microphone, an amplifier and a power source such as a battery. The rear portion of the temple member 10 advantageously houses a bone conduction receiver 14 which is formed in accordance with the principles of the present invention as explained in greater detail hereinbelow. As illustrated in FIGURE 1, the portions of the bone conduction receiver 14 which protrude from the inner surface of the temple member casing comprise a large area contact button 16 adapted to be positioned against the mastoid area of the wearer and an annular acoustic seal 18, surrounding but spaced from the contact button 16.

Reference is now made to FIGURES 2, 3, 4 and 5 for a more detailed discussion of the construction of the bone conduction receiver embodying the present invention. As there shown, the contact button 16 advantageously takes the form of a resilient pouch or pillow 20 filled with a plurality of small particles 21 to enable the contact button 16 to conform to the contour of the mastoid area upon contact.

Those skilled in the hearing aid art are familiar with the deficiencies of the small, rigid contact buttons heretofore used in bone conduction hearing aids. The present invention, through the use of a large, resilient pouch filled with a plurality of small particles provides many advantages. Since the pouch 20 conforms to the mastoid contour, it provides uniform contact pressure throughout the area of contact, hence giving a greater uniformity of bone conduction receiver response. It further serves to increase wearer comfort by the elimination of high contact pressure areas. Further, the contact button 16 can be made with contact areas of much greater size than that present in present-day devices to further facilitate wearer comfort and receiver etficiency.

In practice, it has been found advantageous to construct such a contact button 16 with a resilient pouch 20 formed of a suitable plastic material such as vinyl and to utilize spherical glass beads within the pouch 29, as illustrated by the small spherical particles 21. The contact button 16 advantageously is mounted on a pedestal platform 22. In one preferable embodiment of the invention, it has been found desirable to form the pedestal platform 22 of a suitable light-weight material, such as aluminum, having a surface area approximately the same as the lower surface of the contact button 16.

The pedestal platform 22 is mounted on a pedestal 24, also of a suitable light-weight material such as aluminum, which in turn is supported by the upper magnetic pole piece 26. In accordance with a salient feature of this invention, the receiver comprises a pair of magnetic pole pieces having resilient hinge means connected to one end of each of the pole pieces to position the latter in spaced, vibratable relation relative to each other.

This unique construction is embodied in the illustrated device by means of the upper magnetic pole piece 26, the lower magnetic pole piece 28, and the resilient hinge member 3% connected to one end of each of said pole pieces. As more clearly illustrated in FIGURE 4 of the drawing, the upper magnetic pole piece 26 comprises a generally rectangular arm 32 having an off-set shoulder 34 at one end thereof. Similarly, the lower magnetic pole piece 28 comprises a generally rectangular arm 36 having an offset shoulder 38 at one end thereof. The resilient hinge member 30 advantageously is comprised of a U-shaped spring member, preferably of magnetic steel, which is adapted to fit over off-set

shoulder portions

34 and 38 of the magnetic pole pieces so as to provide a compact, magnetic assembly structure.

Each magnetic pole piece may be secured to the resilient hinge 30 by a suitable fastening means, as for example, by means of the threaded apertures and screws shown in FIGURES 2, 3, and 4 of the drawing. Thus, the upper magnetic pole piece 26 may be securely fastened to the upper arm of resilient hinge 30 by means of the threaded fasteners 40, and in a similar manner, the lower magnetic pole piece 36 may be securely fastened to the lower arm of resilient hinge 30 by means of the threaded fasteners 42. When the magnetic structure is assembled, as illustrated in FIGURE 3 of the drawing, the upper and lower magnetic pole pieces are in spaced relation relative to each other to define an air gap therebetween, and are adapted for vibration relative to each other in response to exciting current from the hearing aid amplifier.

A magnet 44 is mounted on the lower pole piece 28 so as to be positioned in the air gap between the spaced pole pieces. Advantageously, the magnet 44 may be a cylinder of a suitable magnetic material such as Alnico 5 or the like. An electrically energizable exciting coil 46 wound on a suitable bobbin 48 is positioned around the magnet 44 such that energization of coil 46 by the application of exciting current at the

coil terminals

50 and 52 causes the upper magnet pole piece 26 to be vibrated relative to the remainder of the magnetic assembly at a frequency and with amplitude determined by the characteristics of the exciting current.

Thus, those skilled in the art will appreciate that if the output of a hearing aid amplifier is connected to the

coil terminals

50 and 52, the contact button 16 will be vibrated against the mastoid area of the wearer in a manner corresponding to the sound waves detected and amplified by the hearing aid.

In the construction and assemby of the present invention, it has been found advantageous to magnetize the magnet 44 after the magnetic structure has been assembled in the manner described hereinabove. This results in the use of less magnetic material which is of great advantage in reducing the cost of construction and in reducing the over-all weight of the hearing aid.

In accordance with a further feature of this invention, a highly desirable degree of low frequency response can be obtained with a smaller physical reaction mass than that required in the prior art bone conduction hearing aids. Towards this end, the lower magnetic pole piece 28 forms a part of the reaction mass of the receiver and an additional reaction mass 54 is adjustably positioned at one end of the lower magnetic pole piece 28 to permit selective adustment of the lower frequency response. The additional reaction mass 54, which may be formed of lead for example, advantageously is provided with one or more pins 56 extending therefrom and the lower magnetic pole piece 28 is formed with a suitable elongated aperture 58 for slidably receiving each pin 56 of the reaction mass 54. As a result of this construction, the additional reaction mass 54 may selectively be moved toward or away from the lower magnetic pole piece 28 to enable adjustment of the receiver low frequency response.

netic pole piece 26. The upper magnetic pole piece 26 may be provided with a plurality of spaced, threaded openings 60 adapted to receive a suitable threaded fastener 62 which is positioned through the pedestal platform 22 and the pedestal 24 to fasten the platform, pedestal and upper magnetic pole piece together. Thus, as particularly illustrated in FIGURE 3, for example, the threaded fastener 62 may selectively be positioned in any of the internally threaded openings 60 upon assembly of the receiver to adjust the high frequency response to a desired characteristic.

While the particular embodiment of the invention i1- lustra-ted in the drawings has been shown with a slidable adjustment for low frequency response and a discrete adjustment for high frequency response, it will be obvious to those skilled in the art that these adjustments may be made either continuously or discretely variable as desired, fully within the spirit and scope of the present invention.

In accordance with a highly important feature of this invention, the magnetic structure and contact button assembly of the receiver is mounted in a hearing aid case by unique pre-loaded torsion suspension means to provide a desired amount of static bias pressure of the receiver against the mastoid area of the wearer. This novel preloaded mounting of the receiver provides the desired bias pressure independent of frame stiffness adjustment in an eyeglasses hearing aid to thereby eliminate any stressing or bending of the plastic parts of the eyeglasses temple members as now required in contemporary bone conduction hearing aid eyeglasses,

This highly important characteristic of the present invention is achieved in the illustrated embodiment by means of the annular rubber torsion mounts 64 and 66 which are sandwiched between the hearing aid receiver and the hearing aid case.

As particularly illustrated in FIGURES 2 and 4 of the drawing,

suitable fender members

68 and 70 may be secured as by soldering, to opposite sides of the upper magnetic pole piece 26, but free of the lower magnetic pole piece 28, for receiving the annular torsion mounts 64 and 66. The internal side walls of the hearing aid case 10 may be suitably recessed, as at 72 and 74, to receive the annular torsion mounts 66 and 64, respectively. In the assembly of the receiver into the case, the annular torsion mounts 64 and 66 are positioned within the wall recesses 72 and 74 and are adhesively fastened thereto in a manner so as to automatically provide a pro-selected loading pressure of the contact button 16 against the mastoid area when the hearing aid is in wearing position.

Those skilled in the art will readily appreciate that other types of torsion mounts, such as a suitable torsion spring, could be used in lieu of the annular rubber torsion mounts 64 and 66. In practice, it has been found that the receiver should be mounted in the case with about 10 ounces of static bias pressure to insure that the receiver does not leave the head or the skin during dynamic excursions of the receiver. Heretofore, this static bias pressure has been provided by the compliance of the eyeglasses frame and/or stiffening springs, but the present invention eliminates these unsatisfactory prior art means for providing the desired static bias pressure.

It is a still further feature of this invention to provide the receiver with a suitable acoustic sealing means around the contact button 16 so that when the contact button is depressed against the mastoid areaas illustrated in FIG- URE 5an eificient acoustic seal is provided against the head of the wearer. In accordance with this embodiment of the invention, a fluid filled annular member 18 is positioned on the hearing aid case so as to completely surround the contact button 16. As shown in FIGURE 3, the contact button 16 normally extends above the acoustic seal 18 when the hearing aid is not in wearing position due to the pro-loaded static bias pressure afforded by the torsion mount described hereinabove. However, when the hearing aid is positioned against the mastoid area, as illustrated in FIGURE 5, the contact button 16 is depressed against its torsion mount to provide the desired static bias pressure against the mastoid area and the annular acoustic seal 18 provides high acoustic attenuation to acoustic radiation emanating from the vibrating element.

While there has been shown and described a specific embodiment of the present invention, it will, of course, be understood that various modifications and alternative constructions may be made without departing from the true spirit and scope of the invention. Therefore, it is intended by the appended claims to cover all such modifications and alternative constructions as fall within their true spirit and scope.

What is claimed as the invention is:

l. The improvement of an electroacoustic bone conduction receiver comprising first and second magnetic pole members, resilient hinge means connected to one end of each of said pole members to position said pole members in spaced, vibratable relation relative to each other, electrically energizable electromagnetic means positioned on said first pole member and in operative association with said second pole member such that energization of said electromagnet means provides vibration of said sec ond pole member relative to said first pole member at a frequency determined by the energizing current, a reaction mass supported by said first pole member and relatively movable thereon for enabling adjustment of the low frequency response of said bone conduction receiver, a contact button mounted on said second pole member for vibration therewith against the skin of the wearer, said contact button comprising a resilient pouch filled with a plurality of small particles to enable said contact button to conform to the surface contour of the skin, selectively movable support means for supporting said contact button on said second pole member and for enabling adjustment of the high frequency response of said bone conduction receiver, and torsion mounting means attached to said receiver for mounting the latter within a case with a desired biasing force against the skin of the wearer.

2. The improvement of an electroacoustic bone conduction receiver comprising first and second magnetic pole members, resilient hinge means connected to one end of each of said pole members to position said pole members in spaced, vibratable relation relative to each other, electrically energizable electromagnetic means positioned on said first pole member and in operative association with said second pole member such that energization of said electromagnet means provides vibration of said second pole member relative to said first pole member at a frequency determined by the energizing current, a contact button mounted on said second pole member for vibration therewith against the skin of the wearer, said contact button comprising a resilient pouch filled with a plurality of small particles to enable said contact button to conform to the surface contour of the skin, and torsion mounting means attached to said receiver for mounting the latter within a case with a desired biasing force against the skin of the wearer.

3. The improvement of an electroacoustic bone conduction receiver comprising first and second magnetic pole members, resilient hinge means connected to one end of each of said pole members to position said pole members in spaced, vibratable relation relative to each other, electrically energizable electromagnetic means positioned on said first pole member and in operative association with said second pole member such that energization of said electromagnet means provides vibration of said second pole member relative to said first pole member at a frequency determined by the energizing current, and a contact button mounted on said second pole member for vibration therewith against the skin of the wearer, said contact button comprising a resilient pouch filled with a plurality of small particles to enable said contact button to conform to the surface contour of the skin.

4. The improvement of an electroacoustic bone conduction receiver comprising first and second magnetic pole members, resilient hinge means connected to one end of each of said pole members to position said pole members in spaced, vibratable relation relative to each other, elec trically energizable electromagnetic means positioned on said first pole member and in operative association with said second pole member such that energization of said electromagnet means provides vibration of said second pole member relative to said first pole member at a fre quency determined by the energizing current, and a contact button mounted on said second pole member for vibration therewith against the skin of the wearer.

5. The improvement of an electroacoustic bone conduction receiver comprising first and second magnetic pole members, resilient hinge means connected to one end of each of said pole members to position said pole members in spaced, vibratable relation relative to each other, electrically energizable electromagnetic means positioned on said first pole member and in operative association with said second pole member such that energization of said electromagnet means provides vibration of said second pole member relative to said first pole member at a frequency determined by the energizing current, a contact button mounted on said second pole member for vibration therewith against the skin of the wearer, and torsion mounting means attached to said receiver for mounting the latter within a case with a desired biasing force against the skin of the wearer.

6. The improvement of an electroacoustic bone conduction receiver comprising first and second magnetic pole members, resilient hinge means connected to one end of each of said pole members to position said pole members in spaced vibratable relation relative to each other, electrically energizable electromagnetic means positioned on said first pole member and in operative association with said second pole member such that energization of said electromagnet means provides vibration of said second pole member relative to said first pole member at a frequency determined by the energizing current, a reaction mass supported by said first pole member and rela tively movable thereon for enabling adjustment of the low frequency response of said bone conduction receiver, a contact button mounted on said second pole member for vibration therewith against the skin of the wearer, and selectively movable support means for supporting said contact button on said second pole member and for enabling adjustment of the high frequency response of said bone conduction receiver.

7. The improvement of an electroacoustic bone conduction receiver comprising first and second magnetic pole members, resilient hinge means connected to one end of each of said pole members to position said pole members in spaced, vibratable relation relative to each other, electrically energizable electromagnetic means positioned on said first pole member and in operative association with said second pole member such that energization of said electromagnet means provides vibration of said second pole member relative to said first pole member at a frequency determined by the energizing current, a resilient contact button mounted on said second pole member for vibration therewith against the skin of the wearer, said contact button having a relatively large surface area adapted to conform to the surface contour of the skin, and torsion mounting means attached to said receiver for mounting the latter within a case with a desired biasing force against the skin of the wearer.

8. The improvement of an electroacoustic bone conduction receiver comprising first and second magnetic pole members, resilient hinge means connected to one end of each of said pole members to position said pole members in spaced, vibratable relation relative to each other, electrically energizable electromagnetic means positioned on said first pole member and in operative association with said second pole member such that energization of said electromagnet means provides vibration of said second pole member relative to said first pole member at a frequency determined by the energizing current, a resilient button adapted to conform to the contour of the skin mounted on said second pole member for vibration therewith against the skin of the wearer, acoustic sealing means positioned around said resilient contact button for attenuating acoustic radiation from said receiver when the contact button is positioned against the skin of the wearer, and torsion mounting means attached to said receiver for mounting the latter within a case with a desired biasing force against the skin of the wearer.

9. The improvement of an electroacoustic bone conduction receiver comprising first and second magnetic pole members, resilient hinge means connected to one end of each of said pole members to position said pole members in spaced, vibratable relation relative to each other, electrically energizable electromagnetic means positioned on said first pole member and in operative association with said second pole member such that energization of said electromagnet means provides vibration of said second pole member relative to said'first pole member at a frequency determined by the energizing current, a reaction mass supported by said first pole member and relatively movable thereon for enabling adjustment of the low frequency response of said bone conduction receiver, a contact button mounted on said second pole member for vibration therewith against the skin of the wearer, selectively movable support means for supporting said contact button on said second pole member and for enabling adjustment of the high frequency response of said bone conduction receiver, acoustic sealing means positioned around said contact button and effective when the contact button is positioned against the skin of the wearer to attenuate undesirable acoustic radiation from said receiver, and torsion mounting means attached to said receiver for mounting the latter within a case with a desired biasing force against the skin of the wearer.

10. The improvement of an electroacoustic bone conduction receiver comprising first and second magnetic pulse members, resilient hinge means connected to one end of each of said pole members to position said pole members in spaced, vibratable relation relative to each other, electrically energizable electromagnetic means positioned on said first pole member and in operative association with said second pole member such that energization of said electromagnet means provides vibration of said second pole member relative to said first pole member at a frequency determined by the energizing current, a resilient, skin conforming, contact button mounted on said second pole member for vibration therewith against the skin of the wearer, a fender securely attached to each side of said second pole member, and annular rubber torsion members attached to said fenders for mounting the receiver within a case with a desired biasing force against the skin of the wearer.

No references cited.