US 2643729 A
Description (OCR text may contain errors)
Patented June 30, 1953 UNITE-D STATES PATENT OFFICE AUDIO PICKUP DEVICE Charles C. McCracken, Chicago, Ill.
Application April 4, 1951, Serial N o. 219,243
The present invention relates tovaudio pickup devices nding particular though by no means exclusive utility in connection with hearing aids.
It is a general object of the present invention to provide a novel attachment for a hearing aid which makes the reproduction of sound more pleasant to the user and which increases the ef'- fectiveness of the aid in overcoming deciencies in hearing. v
Another object of the invention is to provide an audio pickup deviceincluding a microphone element together with physical means operative to limit maximum loudness to the end that reproduction of sharp or sudden noise impulses is minimized.
A further object is to provide an' audio pickup device of the above general character in a hearing aid whereby to eliminate painful and disturbing sensations to the user which result from Sharp noises such, for example, as those produced by a slamming door, a clanging'bell, `or the like.
Still another object lies in the provision of means of a simple character which is effective with the aforementioned audio pickup deviceto minimize the objectionable noises incident to the wearing of a hearing aid known as clothing scratch.
The objects of the inventionV thus generally set forth together with other objects and ancillary advantages are attained by the construction and arrangement shownby `way of illustration in the accompanying drawing,r in which: Y
Figure l is a perspective View of a hearing aid including an audio pickup device embodying the features of thel present invention.
Fig. 2 is a fragmentary vertical section taken substantially in thefplane of li-ne 2 2 in Fig. 1.
Fig. 3 is a perspective view of a modied form of hearing aid embodying the features of the present invention.
Fig. 4 is a vertical section taken substantially in the plane of line 4--4 in Fig. 3.
Fig. 5 is a' fragmentary elevational view of a microphone arrangement intended for use with public address `systems and the like and showing in dotted section an audio' pickup device embodying the features of the invention.
While illustrative embodiments of the invention have been shown in the drawing and will herein be described in detail. it is to be understood that the intention is not to limit the invention to the specific embodiments shown, but, on the contrary, it is intended to cover all modiiications and alternative constructions falling within the spirit and scope of the inventicn as expressed in the appended claim,
Users of hearing aids have been continuallyy plagued by the reproduction by the aids of sharp disturbing noises and scratches. For this reason numerous attempts have been made to overcome or eliminate such objectionable noises which attempts include the provision of acoustical labyrinths, microphone baffles, and various sound absorbing or deadening schemes. To the same end, much effort has been expended in the design of electronic circuits for such devices which serve to limit maximum loudness and to lter out certain frequency ranges. Not only have these attempts not permitted of economical manufacture, but more important, none has proved entirely effectual.
The present invention provides a means of a simple and practical character which has proved eifectual to minimize the reproduction of such noises so that when utilized with conventional hearing aid circuits objectionable noises are reduced substantially below the discomfort threshold level. K
In accordance with the invention, there is provided n combination with a microphone element a passageway or `audio canal to the microphone element for the conduction of an audio wave thereto, and an audio filter shield arranged at the outer end of the passageway` surrounding the same, for receiving and guiding an audio wave impinging thereon into said passageway. The audio filter shield has a flared portion which lies predominantly ony one side of the passageway, its surface being interrupted by generally longitudinal ridges 'and valleys and having a curled peripheral flange, the same being formed in the manner of a human ear.
By way of illustration. an audio pickup device I!) embodying the instant invention is shown applied to a conventional hearing aid which includes a generally rectangular case l 2, The case i2 may conveniently be formed of a thermosetting plastic. In the form of the invention illustrated in Figs. l and 2, the audio pickup deviceV Iii .is formed integral with the hearing aid case I 2 and includes a passageway or canal Hi formed by a tubular projection I6 extending inwardly from the front wall of the hearing aid case v l2. A microphone element, generally designated i8, is supported adjacent the inner end of the passageway I4 in any suitable manner. Preferably the microphone I8 is enclosed within a resilient coverm ing 2li which serves both to shock-mount the same and to shield it from the reception of audio waves from directions other than by way of the passageway I4.
The outer end of the passageway I4 is out wardly iiared and merges smoothly with an audio filter shield 22 which, as above noted, is formed integral with the case I2. The shield 22 is of inverted, generally pear-shaped outline and in 5 cludes a curled peripheral flange or helix 2 bordering a depressed valley area 2E. Adia nt to the valley area is an arcuate, generally lo tudinal ridge or antihelix 2S `which borders flared open end or concha of the passageway irl. 1 The shield also includes an arcuate tab-dike projection or tragus 29 which partially overlies the outer end of the passageway is at one side thereof.
Another form of the invention is shown in Figs. 3 and 4 wherein the audio pickup device i8 is formed separately from the case 2A of the hearing aid in which it is incorporated. Preferu ably the case I2A is provided with an inwa ly extending boss 30 which denes a recess 332 within which the pickup device I is partially re ceived. Adjacent the lower right-hand corner of the boss is provided an opening .ifi for the reception of the tubular projection le of the pick up device which defines the passageway or audio canal I4. The microphone element It of the device is, of course, disposed at the inner end of the passageway I4 as previously described.
In this instance the audio filter shield 2'? and. the tubular projection Iii comprise a or molding of resilient material such, for as soft rubber or pliable plastic. As shown, the microphone element I8 is molded within the projection I6 and the latter is provided with an irrtegral rear wall Ia so as to completely enclose the microphone element I8.
Hearing aids are usually supported on an inne'1 garment in a manner such that they are li' rom View by an outer garment. For exa la the instrument may be supported in a shirt pocket and concealed by the wearers coat. This Y jects the instrument to highly objection noise resulting from therubbing together oi t' a outer layer of clothing against the'inner cr rui- Mi lying layer, or by the rubbing of an outer layer directly against the case of the instrument. The noise produced by this rubbing together of clothing layers produces substantially the same sensa"- tion to the wearer of the instrument as that prem duced in the normal ear by the rubbing together of two pieces of sandpaper. In order to climi-- nate the production of such noise, or at least to minimize the same, the hearing aid ifi/.A is provided with a covering or envelope [iu of soft, resilient, porous material such, for example, 55 sponge rubber. An opening 42 is provided in the covering of the same general shape as of the recess 32 and the audio pickup device Iii in order not to hinder the operation of the latter and block off the impingement of audio air waves thereon.
It will be observed that the inner surface of the covering 4D lies intimately against the outer surface of the hearing aid casing IZA. Thus there is substantially no relative motion between these two surfaces. If desired, the covering may be fixed to the casing I2A as by cementing. By virtue of the soft resilient character of the covering 40 a layer of clothing bearing thereon tends to cling to the outer surface of the covering and not slide thereover. It will be apparent, therefore, that since there is substantially no movement between the covering 4t and the case I2A, and little or no movement between the clothing layer and the outer surface of the covering even though the clothing layer might more with respect to the casing I2A, such moi/ein will be accommodated within the resilient coveru ing 40 without the production of any rasping or scratching noise. Should there be movement the clothing layer with respect to the cove the character of the covering not only minii any noise production but also will absorb it to the end that it is not picked up by the audio device IU.
Turning now to Fig. 5 of the drawing, there shown is an acoustic pickup device incorporated within a microphone structure for a conventional public address system or the like. As shown, the structure includes an audio pickup device It like that illustrated in Figs. 3 and 4 housed within a generally ellipsoidal casing Sii. The latter includes an imperforate rear shell porm tion 50a and a foraminated or mesh front portion 5017, and the composite structure is sup ported on a suitable stand 52. The audio filter shield 22 is disposed substantially in the transverse plane defined by the junction between the two casing sections 50a and 50D, substantially transversely of the casing 50.
It has been Observed that the use of an audio pickup device of the character described with conventional amplifying equipment operates to substantially eliminate the production of reedback unless the device is placed directly in front of and in close proximity to the speaker of such equipment.
I claim as my invention:
In a hearing aid having a microphone element, the combination of a case for the hearing aid and an audio pickup device, the latter comprising means defining a canal for conducting an audio wave to the microphone element disposed within said case, and an audio filter shield arranged at the outer end of said canal and generally surrounding the same, said filter shield including a flared portion lying predominantly on one side of said canal and including a tablike projection on the opposite side of said canal partially overlying its outer end, the outer surface of said iiared shield portion being interrupted by smoothly merging arcuate ridges and valleys and terminating in a curled peripheral flange, said filter shield being integrally formed with said Acase and lying generally in a plane parallel and closely adjacent the outer surface of said case.
CHARLES C. MCCRACKEN.
' References cited irl the sie of this patent UNITED STATES PATENTS Number Name Date 1,485,918 Hearn Mar. 4, 1924 1,601,063 Frederick Sept. 28, 1925 2,148,477 Koch Aug. 31, 1935 2,468,721 Volkmann Apr. 26, 1949