Abstract:
An in-the-ear hearing aid having an electric/acoustic transducer system and a freely vibrating membrane in acoustic communication with the hearing aid transducer and the hearing aid surroundings. The membrane seals the hearing aid from its surroundings to aid in protecting the hearing aid from dirt and debris.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an in-ear hearing aid comprising an electric/acoustic transducer system as defined in the preamble of claim  1 . The invention furthermore relates to a method for manufacturing an in-ear hearing aid as claimed in the preamble of claim  9 . 
   Soiling is a problem in in-ear hearing aids, in particular as regards the acoustic device&#39;s output facing the ear drum. Such soiling degrades hearing-aid operation and requires periodic cleaning. The conventionally used aperture in the hearing aid housing used as acoustic output and coupled to the electric/acoustic transducer in this respect entails significant cleaning problems. 
   The European patent document 0,548,580 discloses using a membrane at the in-ear hearing aid to seal said housing, said membrane being coupled, as in the case of the actual loudspeaker diaphragm, with the loudspeakers motor drive. As a result the hearing aid design is comparatively more complex and so are the steps required to couple the said membrane to the loudspeaker drive and to assure that said membrane shall not be degraded by cleaning. 
   BRIEF SUMMARY OF THE INVENTION 
   The objective of the present invention is elimination of the above stated drawbacks of the known solutions and to propose an in-ear hearing aid of which the design shall fully meet the cleaning requirements in simple manner. 
   This goal of the invention is attained in that the acoustic output of the electric/acoustic transducer system at the in-ear hearing aid is separated by a freely vibrating membrane of said hearing aid from the hearing aid&#39;environment. 
   It is the insight of the invention that by appropriately designing the acoustically effective spaces in the hearing aid and by appropriately controlling the membrane characteristics, acoustic impedance matching can be achieved so that such a freely vibrating membrane practically shall not affect the acoustic transfer function of the hearing aid at the output side of said transducer, that is, the said membrane shall be acoustically transparent. 
   Where desired, such a membrane also may be used as a damper. 
   In another preferred embodiment of the in-ear hearing aid of the invention, the freely vibrating part of the membrane is made of a single material, which preferably shall be elastomeric, for instance being latex or a silicone rubber. In a preferred embodiment, moreover, the membrane of the invention shall be of constant thickness at least within said vibrating part. 
   The cost of making the hearing aid is only trivially increased by introducing the above membrane. The preferably used membrane material, for instance latex or silicone, is highly economical and is manufactured in low, uniform thicknesses, it is stress-resistant and unobjectionable as regards making contact with living tissue. 
   In an especially preferred embodiment, the said membrane is mounted very close to the hearing-aid output, and as a result indentations and accumulations at the hearing aid that would raise cleaning difficulties are eliminated at least in the vicinity of said output. Moreover the acoustic output of the transducer system can be connected by a tube stub to the acoustic output aperture, however and in preferred manner, the acoustic output of the electric/acoustic transducer system shall be mounted in the direct vicinity of the output aperture of the hearing-aid housing. 
   In a further embodiment which is exceedingly advantageously with respect to hearing-aid manufacture, the hearing-aid output aperture consists by a lamellar sealing element connected to the remaining hearing-aid housing, for instance by welding or bonding. And in a further preferred manner, the membrane sealing the hearing-aid output aperture shall be integral with said sealing element, or it may be separate. Where desired the membrane may be slipped like a hose over the hearing-aid housing. 
   If the said sealing element is integral with the membrane, then the requirements relating of materials applying to the membrane also must apply to the sealing element. Preferably the said sealing element then shall be made of a elastomeric material, for instance latex or silicone. 
   The manufacturing method of the invention relating to the cited in-ear hearing aid furthermore is characterized by the statement of claim  9 . Therein the transducer system is situated in a blind aperture in a support plate of which the base is formed by a membrane. Upon relative motion of support plate and hearing-aid housing, the transducer system then shall be inserted from the end constituting the acoustic output of the hearing-aid housing into this housing. Next the support plate is connected to the hearing-aid housing, for instance by bonding or welding, and thereafter the support plate is molded along the contour of the hearing-aid housing. 
   Such a procedure is extraordinarily well suited to automate the assembly of the in-ear hearing-aid housing and of the electric/acoustic transducer system as well as of the membrane. 
   In a preferred implementation of the manufacturing method of the invention, the membrane is integral with the support plate, this support plate preferably being made of a elastomeric material such as latex or silicone, or first the membrane in the form of a sheet and with apertures is deposited on the support plate and in this manner the blind apertures are formed first. 
   It has been conventional practice so far to manually carry out the assembly of in-ear hearing-aid housings and electric/acoustic transducer systems. Such a procedure eliminates the formation of acoustically shunting elements between the loudspeaker in the electric/acoustic transducer system and the hearing-aid housing whereby there would be feedback of the acoustic signals either directly or through the adjacent ear tissue into the acoustic/electric transducer at the input of the transducer system. Therefore, as already stated, the transducer system is manually inserted into the hearing-aid housing so as to be omnidirectionally spaced from it and to fix it in position therein. 
   In another aspect of the present invention, its objective is to substantially reduce the heretofore conventionally entailed cost of manufacture. This goal is attained basically by means of the statement of claim  12  in that the transducer system is inserted in automated manner into the hearing-aid housing. Compared with conventional procedure, wherein the transducer system is slipped from “above” into the hearing-aid housing, another and much preferred implementation of said manufacturing method of the invention inserts the transducer system through an aperture constituting the acoustic output of the hearing-aid housing into this housing. In a further much preferred implementation, the method of the invention is implemented in that the transducer system is positioned in a seating aperture of a support plate and then, on account of relative motion between the support plate and the hearing-aid housing, this transducer system is inserted from the end constituting the acoustic output of the hearing-aid housing into said housing. Especially as regards this further preferred implementation, whereby thereupon the support plate is joined to the hearing-aid housing, for instance by bonding or welding, and thereafter the support plate is contoured along the outer contour of the hearing-aid, the invention achieves positioning and affixing the transducer system in said support plate, as a result of which positioning the transducer system in the hearing-aid housing is reduced to the simple task of securing accurate advancing motions of hearing-aid housing and support plate. As already mentioned, such a procedure is ideal for automated assembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is elucidated below in relation to the attached Figures. 
       FIG. 1  diagrammatically shows a transducer system in the form of a module, 
       FIG. 2  is a diagrammatical simplification of a longitudinal section of one embodiment of a transducer system, 
       FIG. 2   a  is another diagrammatical embodiment of the transducer of  FIG. 2  fitted with a membrane of the invention, 
       FIG. 3  diagrammatically shows the installation of a transducer system into an in-ear hearing aid of the invention fitted with a membrane of the invention, 
       FIG. 4  is a view similar to  FIG. 3  of a further possible integration of a transducer system fitted with the membrane of the invention into an in-ear hearing of the invention, 
       FIG. 5  is a view similar to  FIG. 3  or  FIG. 4  of a further preferred embodiment variation of that portion of an in-ear hearing aid which constitutes the acoustic output of the hearing aid, and 
       FIGS. 6   a - 6   c  diagrammatically show the sequence of a manufacturing method of the invention applied to an in-ear hearing aid as regards assembling the electric/acoustic transducer system and the hearing-aid housing. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  diagrammatically shows a transducer module serving herein to elucidate the principles of acoustic coupling of this hearing aid. The transducer module  1  comprises a loudspeaker housing  3  wherein is supported the loudspeaker diaphragm  5 . This loudspeaker diaphragm  5  is powered by a motor drive  7  merely indicated in schematic manner. The loudspeaker diaphragm  5  divides the loudspeaker housing  3  into a front chamber R 1  and a rear chamber R 2 . One of the two cited chambers, for instance the rear chamber R 2 , is acoustically coupled through acoustic coupling apertures  9  with an acoustic gap  11  subtended between the loudspeaker housing  3  and the enclosure  13 . The enclosure  13  and hence the gap  11  substantially entirely enclose the loudspeaker housing  3  except for elastic braces  15  by means of which the loudspeaker housing is spaced and supported in substantially “floating” manner within the enclosure  13 . As shown in  FIG. 1 , the front chamber R 1  communicates with the acoustic output A A  of the transducer module  1 . 
   In this design, on account of the substantially free-floating support of the loudspeaker housing  3  in the enclosure  13 , the loudspeaker effect on the enclosure  13  is acoustically decoupled from this enclosure. By significantly enlarging the rear diaphragm chamber R 2 , namely by including the gap  11 , the acoustic behavior of the transducer module  1  is significantly improved over that of the loudspeaker system in the housing  3 : the bass of the transducer module is raised by several dB compared to the bass of the loudspeaker system in the housing  3 . 
   In a preferred embodiment of the transducer module  1  invention, this very module shall be fitted with a membrane, as diagrammatically indicated by  17 , at the acoustic output A A . Except for being clamped at its rim, the membrane  17  is vibrates freely. Preferably this membrane is made of a homogeneous material, preferably a elastomeric material such as latex of silicone rubber, and in a further preferred manner, its thickness is constant and about 100 μ, preferably no more than 0.09 mm. 
   By matching the acoustic impedance of the gap  11  to the chamber R 2 , of the chamber R 1  as far as the membrane  17 , of the membrane  17  and any acoustic conductor that might be provided to propagate toward the environment U of the transducer module  1 , the membrane  17  is practically acoustically transparent. 
     FIG. 2  is a cross-section of one embodiment of the transducer module  1 . The references already used in the diagram of  FIG. 1  are used herein also. The loudspeaker housing  3  comprising the coupling apertures  9  is supported by elastomeric bearings  19  on the enclosure  13 . The enclosure  13  is constituted by a cup  20  preferably simultaneously acting as a magnetic shield and for that purpose preferably being made of mu-metal. In any event the cup  20  preferably shall be metallic. The cup  20  is sealed by a cover  22 . The membrane  17  already shown in  FIG. 1  may be mounted directly on the cover  22 . Furthermore the cover  22  and the membrane  17  may very well be integral, in which case however the material of the cover  22  must meet the material requirements of the membrane, for instance regarding elastomeric behavior. Illustratively the entire component  22  shall be made of latex or silicone rubber. Otherwise the membrane  17  is anchored as a separate element on the cover  22 . However the membrane  17  also may be fitted between the acoustic output A 3  in the loudspeaker housing  3  and the aperture in the cover  22 . Preferably however, as shown in FIG.  2 , the membrane  17  is trimmed to be flush with the aperture in the cover  22 , whereby the transducer module  1  as a whole shall be a unit which is sealed and encapsulated per se and which can be cleaned very easily. Such a feature is especially significant if, as shall be discussed further below, the output A A  of the transducer module  1  is situated directly at the acoustic output of a hearing aid. 
   The transducer module, or its enclosure  13 , can be cubic, cylindrical or assume another, arbitrary shape, provided that the required gap  11  substantially enclosing the loudspeaker housing  3  shall be subtended by the loudspeaker housing  3  and the enclosure  13 . Based on the discussion relating to  FIG. 2 ,  FIG. 2   a  shows another embodiment, in merely diagrammatic form. Therein an elastomeric sleeve  17   a  is pulled over the enclosure  13 . Said sleeve  17   a  simultaneously constitutes the cover  22  and the membrane  17 . 
     FIG. 3  diagrammatically shows the segment comprising the output aperture A 24  of an in-ear hearing aid  24 . The transducer module  1  of  FIG. 1 ,  2  or  2   a  is integrated into the hearing-aid housing  26 , namely being situated and kept in position in frictionally or geometrically locking manner by means of straps  28 , in the hearing-aid&#39;housing  26 . This feature is made possible by decoupling the enclosure  13  from the loudspeaker housing  3  in the transducer module in the manner discussed in relation to  FIGS. 1 ,  2  and  2   a . Otherwise the design of the in-ear hearing aid of  FIG. 3  is substantially the same as the known designs because the acoustic output of the transducer module  1  is connected by a tubular stub  300  to the acoustic output aperture A 24  of the hearing aid. 
   The electronic components and the input-side acoustic/electrical transducer system at the in-ear hearing aid  24  comprising the housing  26  are omitted from FIG.  3  and the further Figures because not being essential to the invention. 
   As further shown in  FIG. 3 , the membrane  17  used in the preferred embodiments is integrated in the immediate vicinity of the acoustic output A 24  in the hearing-aid housing  26 . 
   In  FIG. 4 , the transducer module  1  is mounted in frictionally or geometrically locking manner in the immediate vicinity of the acoustic output A 24  of the hearing aid  24 , ie. of the housing  26  as indicated by the diagrammatically shown supports  28   a . In a preferred embodiment mode, the freely vibrating membrane  17  is mounted terminally. 
   As shown in  FIG. 5 , the housing  26  of the in-ear hearing aid  24  consists of a main housing part  24   a , whereas a laminar cover  24   b  is set terminally on the component  24   a  onto which it is bonded or welded. A transducer module  1  described in relation to FIGS.  1  and  2 —or one fitted directly to the loudspeaker housing of a loudspeaker system of the prior state of the art, which in  FIG. 5  includes both and is denoted by  30 —is seated in the output aperture  32  of the cover  24   b  where it is affixed by clamping, bonding etc. If the transducer module  30  shown in generalized form in  FIG. 5  is fitted with an enclosure, that is designed in the manner of  FIGS. 1 and 2  or  2   a , then the hearing-aid housing  26  may again contain positioning and affixation elements again denoted by  28  for said transducer module  1 . 
   A preferred membrane of the above described kind is denoted by  17  also in  FIG. 5  in a preferred position. As discussed further below, the design of  FIG. 5 , whether applied to hearing aids comprising a transducer module as shown in  FIGS. 1 ,  2 ,  2   a  or whether applied to previously known transducer systems, that is with a loudspeaker housing directly on the outside, does offer substantial advantages. Moreover the membrane  17  may be integral with the component  24   b , and in particular the material selection regarding the portion  24   b , which is separate from the remaining housing  26 , can be matched to the requirements placed on the membrane  17 . 
     FIGS. 6   a  through  6   c  schematically show the sequence of a manufacturing method of in-ear hearing aids. 
   As shown in  FIG. 6   a , preferably blind apertures  36  are present in a support plate  34  and receive the transducer systems  30  of the in-ear hearing aids. If these transducer systems  30  are conventional, that is, if comprising an external loudspeaker housing and lacking an enclosure as shown in  FIGS. 1 ,  2 ,  2   a , then the transducer systems  30  preferably shall be firmly anchored in the support plate  34 , for instance by bonding. If on the other hand the transducer systems do comprise external enclosures as shown in  FIGS. 1 ,  2 ,  2   a , then the systems  30  need not be kept firmly joined to the support plate  34 , because, as already discussed and as shown at  28   b  in dashed lines, they may be affixed in frictionally or geometrically locking manner in the corresponding hearing-aid housings  24   a . It is of foremost significance as regards the procedure that on account of relative motion of the plate  34  bearing the transducer systems  30  and a corresponding number of housing parts  24   a , the transducer systems  30  shall not be inserted in the conventional manner from above, but instead from below into those segments of the housing parts  24   a  which face the acoustic output. 
   In case the transducer systems  30  are designed with enclosures, then, after the transducer systems  30  have been inserted in affixed manner into the housings  26 , the support plate  34  may be removed, the transducer systems or modules being positioned and held in place in the housings  24   a . On the other hand if transducer systems lacking an encapsulation enclosure are involved, the transducers  30  remain in the assigned apertures  36  of the plate  34 . The plate  34  is connected to the housing  24   a  for instance by bonding or welding, and, based on the position of  FIG. 6   b , the plate  34  then is trimmed to become flush with the external housing contour (transition to  FIG. 6   c ). 
   The result is the in-ear hearing aid shown in FIG.  5 . However this procedure is preferred for transducer modules designed in the manner of  FIGS. 1 ,  2 ,  2   a , that is fitted with an enclosure. 
   Observation of  FIG. 6  shows that this procedure is unusually well suited to integrate the membrane  17  or another preferred one to act both as soil protection for the acoustic hearing-aid output and as a means assuring simple cleaning. For that purpose the base plate  38  of  FIG. 6   a  of the apertures  36 , which preferably shall be blind holes, shall be directly formed as the membrane. Implementation takes place either by selecting the material of the support plate  34  to match the requirements set on the membrane material and hence designing integrally with the plate  34 , or, as shown in dashed lines in  FIG. 6   a , by forming the blind holes  36  first by laminating the support plate  34 , the apertures still being open end to end, with a sheet  34   b  or the like which then constitutes the membrane  17  of FIG.  5 . 
   The above discussed manufacturing method allows assembling both transducer modules as shown in  FIGS. 1 ,  2 ,  2   a  and also conventional transducer systems, that is comprising an external loudspeaker housing, in the in-ear hearing aid housing, without need for laborious positioning maneuvers. Said assembly can be implemented from that side where the acoustic output is situated. As a result substantially automated assembly is made possible. If, as preferred, the acoustic hearing-aid output shall be protected against soiling from the environment, and allow good cleaning, it is also simultaneously feasible to integrate a covering membrane  17  as discussed above.