Abstract:
A small hearing aid is provided which fits completely in an ear canal of a user wherein a shell as an outer housing of the hearing aid is shaped to closely surround components of the hearing aid to provide a gap between the hearing canal inner walls and the shell to allow flow of air when the hearing aid is mounted in the ear by a mounting element connected to the shell. The mounting element is provided with at least one aperture to allow the air flow. In a fabricating method, an image of the shell is shrunk to closely surround the hearing aid components while maintaining a shape of the ear canal to assure a custom fit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/041,336, filed Apr. 1, 2008, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     It is known to provide a completely-in-the-canal (CIC) hearing instrument (hearing aid) in which an outer housing known as a shell of the hearing aid, is formed in a shape corresponding to the ear canal. An outside surface of that shell is in contact with substantial portions of an inner surface of the ear canal. With such CIC hearing aids, because the hearing aid housing is substantially in contact with the ear canal, a vent cavity inside the shell is provided to allow air flow through the ear canal and thus permit pressure to be equalized between the outside and the inside of the ear drum. This vent cavity or channel also reduces occlusion effects and operation of the hearing aid. Occlusion effects are known in this industry as being a change in hearing acoustics which sounds like being in a tunnel. 
     SUMMARY 
     It is an object to decrease the size of the CIC hearing aid so that it is even smaller than the conventional CIC hearing aid. 
     A small hearing aid is provided which fits completely in an ear canal of a user wherein a shell as an outer housing of the hearing aid is shaped to closely surround components of the hearing aid to provide a gap between the hearing canal inner walls and the shell to allow flow of air when the hearing aid is mounted in the ear by a mounting element connected to the shell. The mounting element is provided with at least one aperture to allow the air flow. In a fabrication method, an image of the shell is shrunk to closely surround the hearing aid components while maintaining a shape of the ear canal to assure a custom fit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a CIC hearing instrument; 
         FIGS. 2A-2F  illustrate method steps in the fabrication of the small CIC hearing aid with a semi-automated method; 
         FIG. 3  is a flow chart for both first and second embodiments of a substantially fully automated method of fabrication of the small CIC hearing aid; 
         FIGS. 4A-4E  are illustrations of the first embodiment of the fully automated method for fabrication of the small CIC hearing aid; 
         FIGS. 5A-5D  are cross-sectional views showing a user adding spline points on the hearing aid shell according to the second embodiment of the fully automated method; 
         FIGS. 6A-6D  illustrate how a user is able to use a detailing tool where the hearing aid shell needs to be modified; 
         FIG. 7  illustrates in a side view a building of the hearing aid shell using a 3D printer in a stereolithography process; 
         FIG. 8  shows a prior art 3D stereolithography printer machine for fabricating the hearing instrument shell; 
         FIG. 9  is a side view of a mushroom cap mounting element, receiver, and receiver shell section having a latching mechanism for the small hearing aid; and 
         FIG. 10  is a detail of the latching mechanism of  FIG. 9  to latch the receiver shell section to one end of the receiver. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     The invention allows fabrication of a CIC hearing instrument smaller than the prior art CIC hearing instrument. The CIC hearing instrument described here has a profile smaller than the ear canal, since the hearing instrument shell is modeled around the components of the hearing instrument such that the shell is “shrunk” to more closely approximate the size of the hearing instrument components, rather than being sized to the ear canal inner walls. A mushroom cap or dome is used to secure the small hearing instrument inside the ear canal. This mushroom cap has an periphery contacting inner side walls of the ear canal near the ear drum and air vent apertures are provided therein as described hereafter. 
       FIG. 1  illustrates a CIC hearing instrument  10  positioned in the ear canal  11  with the ear canal being shown in dashed lines. The mushroom cap or dome  12 , functioning as a mounting element for the hearing instrument  10 , is positioned near the ear drum  11 A in the ear canal  11 . This mounting element or dome  12  comprises a plurality of vent apertures  12 A in a dome wall  12 B, and a periphery or outer peripheral surface  12 C that conforms to and engages the ear canal inner wall  11 B. The vent apertures  12 A permit airflow through the ear canal  11  to and from the ear drum  11 A and through the dome  12  to ensure that pressure on the ear drum  11 A is equalized and also to improve overall acoustical comfort of the hearing instrument  10 . A gap or passage  13  between the inner wall  11 B of the ear canal  11  and remaining portions of the small hearing instrument  10  enables air passing through the vent apertures  12 A to freely pass through the gap  13  between sidewall  11 B and the hearing instrument shell  14  extending from the dome  12 . 
     The hearing instrument  10  has a shell  14  comprising a receiver shell section  14 A having a receiver  18  ( FIG. 9 ) connected to a short mounting section or mounting face  14 D at one end facing the ear drum  11 A that accepts the mushroom cap or dome  12  and a shell section  14 B housing additional components. Also in  FIG. 1 , an optional curved shell section  14 C not employed in  FIGS. 2C-2F  may be provided as a transition section. The end  14 F of the shell section  14 B facing the outer ear, i.e., the direction opposite from the ear drum  11 A, contains the faceplate  60  and controls  62 , as illustrated in  FIG. 1 . The gap or passage  13  runs continuously from the dome  12  to the faceplate  60  on the outer surface  14 E of the shell  14 . The gap or passage  13  is created by the difference between the peripheral dimension  70  of the shell  14  along the length  72  of the shell  14  and the inner dimensions of the ear canal  11 . The size of the gap or passage  13  is determined by measuring the contours of the user&#39;s ear and then sizing the shell  14  accordingly, as explained below. 
     The fabrication of the small hearing aid will now be described with reference to  FIGS. 2A-2F ,  3 ,  4 A- 4 E,  5 A- 5 D,  6 A- 6 D,  7 , and  8 . With the fabrication method, fixed geometries are used to shrink the outer shell to fit the internal components while maintaining a clearance between the shell and the ear canal to provide what is known as an open fit. 
       FIGS. 2A-2F  are computer screens  7  showing computer-aided design (CIC) illustrations of successive steps of the design process.  FIG. 2A  shows a raw impression  8  of the patient&#39;s ear canal for the custom fit. This raw impression  8  is created by a technician first making an impression of a patient&#39;s ear canal with a two part silicon material placed in the patient&#39;s ear which hardens and is then removed. Impression  8  is then scanned with a scanner  9 . Commercially available scanners may be used for this purpose such as the Minolta Sailor 3 Scanner with related software. The scanner  9  and related software outputs what is known as an STL file  9 A based on a cloud of points (point cloud) at an outer periphery of the impression  8 . An STL file is well known in this field and represents a 3D point cloud image. The STL file raw impression image is illustrated at  17  on the computer screen illustration of  FIG. 2A . 
       FIGS. 2A-2F  represent a semi-automated method of fabrication. 
     Creating the raw impression and scanning the raw impression to create an STL file is known prior art. 
     Thereafter as shown in  FIG. 2B , using the raw impression image  17  in  FIG. 2A , an operator manually extracts a portion of the raw impression image to create a detail image  18  of the raw impression image  17 . This detail image is similar to that employed in the construction of a prior art CIC hearing aid shell. In  FIG. 2B , the modeling and detailing of the raw impression image can be performed by commercially available software known in the prior art such as the 3SHAPE modeling software. 
     In  FIG. 2C , the receiver shell section  14 A along with the short mounting shell section  14 D and expanded shell section  14 B form the hearing aid shell  14 . Here, the operator manually shrinks the shell  14  down and around the hearing aid components comprising the receiver and the other hearing aid components like a “shrink fit”. 
     In  FIG. 2D  the shell  14  which has been preshrunk in  FIG. 2C  is now cut to provide a gap in which the receiver shell section  14 A is to be placed between the expanded section  14 B and short mounting shell section  14 D which receives the mushroom cap  12 . 
     In  FIG. 2E , the receiver section  14 C is merged to one end of the expanded section  14 B and also receives the short mounting section  14 D at the other end. 
     In  FIG. 2F , the finished product is provided showing the mushroom cap  12  on the short mounting section  14 D, the receiver  18  comprising receiver modules  18 A,  18 B received in the receiver shell section  14 C, and the expanded shell section  14 B resulting in the finished product (shell  14  connected to mushroom mounting element or cap  12 ). 
     As an alternative to the semiautomatic mode involving manual manipulation by an operator, a fully automated method which automatically shrinks the outer shell  14  to the components by using fixed geometries is provided. As in the case of the semi-automatic method, with the automatic method a clearance is provided between the shell (hearing aid outer housing) and the ear canal that provides the open fit previously described. 
     Three alternative embodiments are provided for the fully automated method. A flowchart of the first and second embodiments is shown in  FIG. 3 . As illustrated there, at step  19  the point cloud is loaded. At step  20 , the rough detail to the desired instrument type is provided. At step  21  components are assembled/arranged. At step  22  the shell is shrunk via the slider bar (embodiment 1) or via 3D spline (embodiment 2). 
     At step  23  a check is made for collision between the components and the shell. At decision block  24 , if there is a collision, then the shell is again shrunk. If there is no collision, as shown at step  25  a smoothing algorithm is applied. Finally, at step  26 , the final detail/touch-up occurs. 
       FIGS. 4A-4E  show how the shell is shrunk to fit the components and thus provide a gap between the shell  14  and the ear canal sidewall  11 B (see also  FIG. 1 ).  FIG. 4A  illustrates the starting shell  27  which is about the size of the ear canal. In  FIG. 4B , the center line is computed, and the shell is sectioned into sectors  28  perpendicular to the center line CL. In  FIG. 4C , the slider bar  29  is moved and each sector  28  will shrink as shown at  28 A until collision of that portion of the shell with the component is detected. In  FIG. 4D , the operator will exercise caution to ensure embedded components can be assembled. In  FIG. 4E , a smoothing algorithm is applied with a cleanup using existing tools where necessary. The completed cleaned up shrunken shell is shown at  30 . 
     With embodiment 1 of the fully automated method, the following occurs: 
     1. The software takes as an input an STL file that represents the receiver shell section around the receiver. 
     2. The software positions the receiver shell section as deep as possible inside a virtual cast representing the inside of the ear canal. 
     3. The software allows the user to position the other hearing aid components inside the virtual cast (ear canal), and shows a clearance equal to the shell thickness value between the other components and the virtual cast (ear canal). 
     4. The software grows the STL shell section towards the other components in such a way that the expanded shell section touches the virtual cast (ear canal) along the longest axis of the canal and has some free space between the expanded shell section and the virtual cast (ear canal) along the short axis of the canal. 
     5. The shrink wraparound the receiver and other components generated as a result of this operation shall have a minimum space required to cover the hearing aid receiver and other components. 
     6. The software ensures that on the face plane the shrink wrapped shell shall touch the virtual cast (ear canal) along the long axis of the canal. 
     7. The software ensures that the shrink wrap shall not collide with the virtual cast (ear canal). This ensures that the shell does not flop in the ear. 
     A second embodiment for the fully automated method is shown in  FIGS. 5A-5D .  FIG. 5A  shows the starting shell  31 . In  FIG. 5B , spline points at  32  are added. 
     In  FIG. 5C  spline points allow the user to grab these spline points and adjust the shape of the shell as shown at  33 . 
     In  FIG. 5D  the shrunken shell  34  results. 
     In the second embodiment for the fully automated method, the following steps occur: 
     1. The software takes as an input an STL file format that represents the receiver shell section and an STL file that represents the expanded shell section around the other components. 
     2. The software positions the STL file that represents the receiver shell section around the receiver as deep as possible inside the virtual cast (ear canal) without collisions with the virtual cast (ear canal). 
     3. The software positions the STL file that represents the expanded shell section around the other components as deep as possible inside the virtual cast without collisions with the virtual cast (ear canal) and an STL file that represents the receiver shell section around the receiver. 
     4. The software grows an STL file that represents the expanded shell section around other components in the direction of an STL file that represents the receiver shell section around the receiver in such way that no collision with the virtual cast (ear canal) occur. 
     5. The software grows an STL file that represents the receiver shell section around the receiver in the direction of an STL file that represents the expanded shell section around the other components in such a way that no collision with the virtual cast (ear canal) will occur. 
     6. The software ensures that the growing surfaces of an STL file that represents the expanded shell section around the other components and an STL file that represents the receiver shell section around the receiver will meet in-between two STL files and allow the seamless merge of two STL files to form a single shell. 
     7. The software merges the grown surfaces of an STL file that represents the receiver shell section around the receiver with the grown surface of an STL file that represents the expanded shell section around the other components to form a single hearing aid shell. 
     A third embodiment for the fully automated method will now be described with reference to  FIGS. 6A-6D . 
     In  FIG. 6A , the shell  35  of the hearing aid with components therein is illustrated. 
     In  FIG. 6B , the user is able to use the detailing tool where the user selects a section  36  of the shell that needs to be modified. 
     In  FIG. 6C , adjustment points  37  are added to the shell in the section  36  to be modified which allows the user to adjust the shell using these points  37 . There is no creating of splines. 
     In  FIG. 6D , the shell has been adjusted as shown at  38  by moving the points  37  downwardly to  37 A, for example to modify the shell. 
     With the third embodiment for the fully automated method illustrated in  FIGS. 6A-6D , the following steps occur: 
     1. The software takes as an input for this approach an STL file that represents the generic small hearing aid shell. 
     2. The software positions the generic small hearing aid shell in the virtual cast (ear canal) in such a way that no collisions occur before an area where bending of the shell is to occur. 
     3. Software bends the hearing aid shell in such a way that the bent hearing aid shell fits in a virtual cast (ear canal) without collisions. 
     For either the semi-automated or fully automated method, the final result is an STL file which is now sent to rapid prototype equipment such as SLA Viper or other 3D printers (also known as SLA stereolithography printers). Such printers are well known in the art and accept STL files to create three dimensional final objects, in this case a fabricated shell. 
     As shown in the two view of  FIGS. 7A and 7B , the commercially available 3D printer shown in  FIG. 8  builds the shell  40  on top of a support material  41 . The building of the shell and the use of support material with the known prior art 3D printer such as  39  (the known SLA Viper, for example) is known in the art. 
       FIG. 9  shows the mushroom cap or dome (mounting element)  12 , the vent apertures  12   a , the receiver  18  formed of modules  18 A and  18 B and the receiver shell section  14 C of shell  14  (forming a pocket) in a side view. The receiver  18  is installed into the receiver shell section  14 A. In order to ensure that the receiver  18  is secured in the pocket-like receiver shell section  14 A, RTV is used and also a mechanical latch system is provided to assure reliability and serviceability. This mechanical latch system is shown as a female latch element  43  and a male latch element  44  in detail in  FIG. 10 . A male latch element is provided on each receiver module  18 A,  18 B and a respective female latch element  43  is provided at opposite sides of the receiver shell section  14 C. As an alternative to male and female latch elements tongue and groove elements may be employed.