Abstract:
A hearing aid device and process for its manufacture, updating, and/or repair including a resilient outer shell and one or more internal units, with the outer shell conforming in shape to at least one of the internal units so that the internal unit is held snugly in place. The outer shell can be replaced using either a destructive or non-destructive disassembly method to re-use at least one of the internal units.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an custom-moulded ear-plug device. 
     This invention addresses the problems typically encountered with conventional hearing aids. The solution to these problems, however, is also suitable for use with other types of custom-moulded ear-plugs such as earphones. 
     The basic premise of this invention lies in the problematic fact that hearing aids are still being manufactured, and replaced, as integral, fixed-design units. Yet when one considers for instance children in their growing stage, it becomes obvious that because of their growth, and as a function of that growth, it is necessary to periodically replace outer-ear and especially in-ear hearing aids. As a result, children are either given cheaper hearing aids or, if they are to use the best available hearing aids, the cumulative cost over the years will be relatively high. 
     Even if in the case of currently available outer-ear hearing aids it were possible to disassemble the device and to retrofit a new shell in adaptation to the recent growth, the cost incurred would be significant. And in the case of in-ear hearing aids it is so high that it could hardly be justified. 
     SUMMARY OF THE INVENTION 
     It is the objective of this invention to introduce an custom-moulded ear-plug device with a built-in module enveloped by a shell, and especially a hearing aid whose shells can be replaced at a reasonable cost. 
     This is achievable with an custom-moulded ear-plug device of the type first above mentioned, whose shell features at least one elastic rubber-like segment that is provided with a module insertion and retrieval port. 
     That makes it possible to mount or slip the shell of the custom-moulded ear-plug device onto or over the module that is introduced in the insertion port and, conversely, to push the module out of the shell. Where necessary, the module may be removed from a given shell by destroying the latter, for instance by cutting it open, disposing of it as a one-way item, and replacing it with a new shell that is slipped over the module. 
     In a preferred embodiment of the custom-moulded ear-plug device per this invention, the shell consists of a rubber-like elastic material. 
     In another greatly preferred embodiment of the custom-moulded ear-plug device per this invention, the elastic properties of the material are additionally utilized in that the shell envelopes and hugs at least part of the module. Indeed, it can be so designed that it not only matches and envelopes at least part of the said module but, given the extensibility of its rubber-like elastic material, that it can be at least partly stretched and friction-mounted. It is therefore particularly preferable for the elastic part to at least partially envelope the module, and at least partially in form-fitting fashion, while it is also entirely possible for a shell section of a material other than a rubberlike elastic material to be form-fitted or even friction-mounted around the module. 
     For another preferred embodiment it is proposed that the port opening of the rubberlike elastic part is smaller than the largest cross-sectional dimension of the module as viewed in a plane perpendicular to the direction of insertion of the module into the port of the shell. This essentially creates a phase plate at the elastic section which, when the module is fully inserted into the shell, will at least in part close over the inserted module. The module itself may be in the form of a single, discrete unit incorporating integrated subassemblies such as perhaps potted electronic components, or the module in question may also consist of two or more sub-units which must be inserted in the shell in the proper sequence. The module preferably encompasses a battery and/or one or more electronic components. 
     Particularly preferred is an custom-moulded ear-plug device per this invention in the form of an in-ear or outer-ear hearing aid. 
     The custom-moulded ear-plug device per this invention as described so far is equally implementable as an outer-ear and as an in-ear custom-moulded ear-plug unit. Specifically for in-ear custom-moulded ear-plug devices, and among these especially for in-ear hearing aids, the above solution is further enhanced by designing the shell to consist of at least two mutually separable sections. This makes it possible in the case of in-ear custom-moulded ear-plugs, especially including hearing aids, to disassemble the shell and to reuse the modules contained therein with a new shell or a new shell section. For example, if for hygienic reasons it is desirable to prevent the reuse of a previously employed shell section, the two sections are so designed that they can be separated only by destroying one or both of these sections. This can be accomplished for instance by means of an interlocking connection of the sections which can be released only by destroying the interlocking catches. The sections may also be separably connected by means of lock mounts, even bayonet-type couplings. Here, too, as a proposed added feature, the shell would envelope at least part of the module, at least hugging it in form-fitting fashion. Again, the module may be designed as an integral, single unit incorporating several sub-units, or it may consist of two or more parts, encompassing at least a battery and at least one electronic component. 
     The custom-moulded ear-plug device according to this invention thus makes it possible to replace the shell without wear on the built-in modules. Apart from the growth-related considerations mentioned above, this is always highly useful where the area of application is subject to change which in the case of in-ear hearing aids means changes in the auditory canal. But given the ease with which the shell of the custom-moulded ear-plug device per this invention can be replaced, it is even possible in the case of outer-ear hearing aids to change shells for reasons of preference, for instance for another color of the hearing aid or in general for considerations of aesthetic appearance. Moreover, the replacement of a shell both in the case of outer-ear and most particularly in-ear hearing aids may be desirable for hygienic reasons, in that the custom-moulded ear-plug shell, essentially serving as a one-way item, is replaced in lieu of a cleaning of the custom-moulded ear-plug device which, after all, is a complex matter. This course of action is employed especially in the case of an infected area of application, i.e. of the ear canal where an in-ear custom-moulded ear-plug device is used, and where at relatively short time intervals it is necessary to insert sterile shells, perhaps even serving as medication dispensers which, depending on the progress of the healing process, must be replaced in any event. It is entirely possible to apply on the outside of the shell a medication which will be diffused for instance into the surrounding tissue, thus employing the custom-moulded ear-plug shell as a medication dispenser. 
     The process according to this invention, as a solution to the problem first above mentioned, is thus further enhanced in that at least one section of the custom-moulded ear-plug shell covering the module is replaced. In a preferred implementation of the process per this invention, the entire custom-moulded ear-plug shell is replaced. Corresponding to the above explanations, a proposed, preferred form of implementation provides for a sleeve-shaped, rubber-like, elastic custom-moulded ear-plug shell to be slipped over the module and, conversely, for the module to be pushed out of the custom-moulded ear-plug shell, or even for the disposable custom-moulded ear-plug shell to be destroyed for instance by cutting it open, following which a new elastic shell is slipped over the exposed module. 
     For in-ear custom-moulded ear-plugs, the process per this invention is further implemented by designing the custom-moulded ear-plug shell as a unit consisting of at least two sections, by separating these sections for the removal of the module, by replacing at least one of the said sections and by reassembling new shell sections with the module. As stated above, when separated at least one of the sections may be destroyed, and even both especially if it is to be made mandatory that a new shell or at least a new shell section be installed. The timing of a forced shell replacement can be set in a way as to coincide with the need to replace the battery where provided. 
     The process according to this invention is particularly suitable for hearing aids incorporating expensive modules. The process per this invention is further indicated for in-ear custom-moulded ear-plugs in the case of changes in the ear canal. Both the custom-moulded ear-plug device according to this invention and the process per this invention also lend themselves to the replacement of the custom-moulded ear-plug shell for sterilization purposes and/or for the application of medications. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified, schematic illustration of a production system employing the preferred manufacturing process for the optimized commercial fabrication of custom-moulded ear-plug devices; 
     FIG. 2 is an illustration, analogous to that in FIG. 1 of another system configuration; 
     FIG. 3 is an illustration, analogous to those in FIG. 1 and 2, of yet another system configuration; 
     FIG. 4 schematically shows an in-ear hearing aid with a conventionally installed cerumen shield; 
     FIG. 5 is an illustration, analogous to that in FIG. 4, of an in-ear hearing aid incorporating a cerumen shield; 
     FIG. 6 shows an in-ear hearing aid with a venting groove proided in conventional fashion; 
     FIGS.  7 ( a ) to ( f ) are perspective, partial illustrations of custom-moulded ear-plug shell surfaces with novel venting grooves; 
     FIG. 8 is a partial, schematic illustration of an custom-moulded ear-plug surface, with a venting groove featuring over its length varied cross-sectional shapes and dimensions; 
     FIG. 9 schematically shows an in-ear custom-moulded ear-plug device with an extended venting groove; 
     FIG. 10 is an illustration, analogous to that in FIG. 9, of an in-ear custom-moulded ear-plug device with multiple venting grooves; 
     FIGS.  11 ( a ) to ( e ) show parts of custom-moulded ear-plug shells with incorporated venting channels displaying mutually different cross-sectional shapes and dimensions; 
     FIG. 12 is an illustration, analogous to that in FIG. 8, of a venting channel in an custom-moulded ear-plug shell which over its length features varying cross-sectional shapes and surface dimensions; 
     FIG. 13 is a schematic illustration, analogous to that in FIG. 9, of an in-ear custom-moulded ear-plug device incorporating an extended venting channel; 
     FIG. 14 is an illustration, analogous to that in FIG. 10, of an in-ear custom-moulded ear-plug device with multiple venting channels; 
     FIG. 15 schematically shows a longitudinal section of an in-ear custom-moulded ear-plug device with a ribbed interior surface; 
     FIG. 16 is a cross-sectional view of part of the custom-moulded ear-plug device per FIG. 15, in which the ribs feature mutually different cross sections; 
     FIG. 17 is a perspective view of part of an custom-moulded ear-plug shell with interior ribbing per FIG. 15 or  16 , in which, over their length, the ribs display varying cross-sectional shapes and dimensions; 
     FIG. 18 is an illustration, analogous to that in FIG. 15, of an in-ear custom-moulded ear-plug unit with exterior ribbing; 
     FIG. 19 schematically shows part of an custom-moulded ear-plug shell, ribbed as in FIG. 18, the ribs featuring mutually different cross-sectional surface dimensions; 
     FIG. 20 is a schematic cross-sectional view of an custom-moulded ear-plug device with external ribbing and perhaps interior ribbing and with an inner space that is at least partially filled with a filler material; 
     FIG. 21 schematically shows part of a longitudinal section of an custom-moulded ear-plug shell with a flexible and resiliently compressible region; 
     FIG. 22 schematically shows a longitudinal section of an in-ear custom-moulded ear-plug device per this invention, with a cavity for accommodating an electronic module; 
     FIG. 23 shows the custom-moulded ear-plug device per this invention, as illustrated in FIG. 22, being slipped over an electronic module; 
     FIG. 24 is a perspective and schematic illustration of an in-ear custom-moulded ear-plug device per this invention, especially an in-ear hearing aid, with a two-part, separable and joinable custom-moulded ear-plug shell; 
     FIG. 25 schematically illustrates part of the integration of acoustic conductors and adapters connecting to an acoustoelectric or, respectively, electroacoustic converter in an custom-moulded ear-plug device; 
     FIG. 26 is an illustration, analogous to that in FIG. 25, of the positioning of two or more acoustic conductors within the shell of an custom-moulded ear-plug device; and 
     FIG. 27 is a simplified signal-flow/functional block diagram of a process and, respectively, a system for its implementation, in which the contouring of an custom-moulded ear-plug unit is adapted to the dynamic movement of the area of application. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The custom-moulded ear-plug-unit design versions discussed following the description of the production process are preferably all manufactured by the said production process. 
     Definition 
     The term custom-moulded ear-plug device refers to a unit which is applied directly outside the pinna and/or at the pinna and/or in the auditory meatus or ear canal. It includes external or pinnal hearing aids, in-ear hearing aids, headphones, noise- and water-blocking ear plugs, and the like. 
     1. Production Process 
     In the preferred production process for fabricating the custom-moulded ear-plug devices described in detail further below, the shape of a particular region in which an custom-moulded ear-plug unit is to be applied, is digitized in three dimensions, whereupon the custom-moulded ear-plug unit or its shell is built up by an additive process. Additive or incremental building i.e. composite structuring processes are also known as Rapid Prototyping. 
     For incremental processes of this nature, already employed in rapid prototyping, reference is made to: 
     The web site: tk.hut.fi/-koukka/RP/rptree.html (1) 
     or to 
     Wohlers Report 2000, Rapid Prototyping &amp; Tooling State of the Industry (2) 
     The different incremental processes currently known and employed in rapid prototyping indicate that laser sintering, laser or stereo lithography or the thermojet process are particularly well suited to the building of custom-moulded ear-plugs or their shells and especially the specific configurations described below. These preferred additive structuring processes are therefore briefly summarized as follows: 
     Laser sintering: A thin layer of hot-melting powder is applied on a powder bed for instance by means of a roller. A laser beam, controlled by the 3D data of the specific individual application area, solidifies the powder layer that corresponds to a slice or sectional layer of the custom moulded ear-plug unit or shell. A solid sectional layer of the custom-moulded ear-plug unit or shell is thus produced in the otherwise loose powder. That layer is then lowered out of the powder deposition plane and a new powder layer is superposed, laser-solidified to constitute another sectional layer, etc. 
     Laser or Stereo lithography: A first sectional layer of the custom-moulded ear-plug unit or shell is solidified on the surface of a liquid photopolymer by means of a UV laser. The hardened layer is dipped and again covered with the liquid polymer. By means of the UV laser the second sectional layer of the custom-moulded ear-plug unit or shell is solidified on the first hardened layer. 
     The positional movement of the laser is itself controlled by the 3D data of the specific application area previously digitized. 
     Thermojet Process: The contouring for a given sectional layer of the custom-moulded ear-plug unit or shell follows a principle similar to that of an ink jet printer, in that liquid is applied based on the digitized 3D data especially of the specific area of application. The sectional image deposited is then allowed to solidify. Again following the principle of an incremental buildup, layer upon layer is deposited in building the custom-moulded ear-plug unit or shell. 
     Relative to additive structuring processes, including the above-mentioned preferred process, reference is made to these other publications: 
     The web site: www.padtinc.com/srv_rpm_sis.htm (3) 
     “Selective Laser Sintering (SLS) of Ceramics”, Muskesh Agarwala et al., presented at the Solid Freeform Fabrication Symposium, Austin, Tex., August 1999 (4) 
     The web site: www.calp.rutgers.edu/RP_Library/process.html (5) 
     The web site: www.biba.uni-bremen.de/groups/rp/lom.html (6) 
     The web site: www. biba.uni-bremen.de/groups/rp/rp_intro.html (7) 
     Donald Klosterman et al., “Direct Fabrication of Polymer Composite Structures with Curved LOM”, Solid Freeform Fabrication Symposium, University of Texas at Austin, August 1999 (7) 
     The web site: Iffme.utexas.edu/sls.html (8) 
     The web site: www.padtinc.com/srv_rpm_sla.html (9) 
     The web site: www.cs.hut.fi/˜ado/rp/rp.html (10) 
     Thus, the basic principle employed in the incremental-buildup or additive-structuring process consists in the deposition of a thin layer of material on a surface, whether that is a full-surfaced blank as in laser sintering or in stereo lithography, or, as in the thermojet process, already a contoured section of the custom-moulded ear-plug unit or shell that is being constructed. The desired sectional shape is then stabilized, i.e. hardened. 
     Once a layer has hardened, a new layer is deposited on it as described above, hardened and bonded to the finished layer underneath. In that fashion, layer by layer, the custom-moulded ear-plug unit or shell is composed by the successive, additive deposition of multiple layers. 
     In commercial production, the preferred method is not to separately deposit and solidify each individual sectional layer for a single specific custom-moulded ear-plug unit or shell, one at a time, but to simultaneously produce several layers for each unit. For example, in laser sintering one laser, typically mirror-controlled, solidifies the sectional layers of several custom-moulded ear-plug units or shells before all hardened sectional layers are jointly dipped. Thereupon, after a new powder layer has been deposited on all hardened and dipped sectional layers, the next multiple sectional layers are formed. Although fabricated in parallel, the individual custom-moulded ear-plug units or their shells are produced as separate units under appropriate digital control. 
     The solidification of multiple sectional layers employs either a single laser beam or more than one laser beam operated and controlled in parallel. 
     In an alternative process, a sectional layer is individually solidified by a laser while concurrently a powder layer is deposited for forming another custom-moulded ear-plug unit or shell. Subsequently that same laser is used to solidify the prepared powder layer representing the sectional layer for the next custom-moulded ear-plug element, while the previously solidified layer is dipped and a new powder layer is deposited on it. In this case the laser alternates intermittently between two or several custom-moulded ear-plug units or shells which are being fabricated, while the idle time of the laser otherwise occurring during the powder deposition for the forming of one of the shells is utilized for the solidification of a sectional layer of another custom-moulded ear-plug unit that is being built. 
     FIG. 1 is a schematic illustration of one process variant in which, by laser sintering or laser or stereo lithography, several custom-moulded ear-plug units or their shells are commercially manufactured in a parallel process. The laser with its control unit  5  and its beam  3  is located above the bed of powder or fluid material. In its position  1  it solidifies the layer S 1  of a first custom-moulded ear-plug unit or shell under the control of the first discrete data set D 1 . Thereupon, a repositioning device  7  moves it into a second position where, under the control of the second discrete data set D 2 , it produces the layer S 2  following another specific contour. Of course, several of the lasers may be moved in unison, for the simultaneous production of more than one individual custom-moulded ear-plug layer. Not until the appropriate lasers  5 , in all their predefined positions, have produced the various individual layers in the laser sintering process will a new powder layer be deposited by the powder feed system  9  or, in the case of laser or stereo lithography, will the solidified layers S be dipped in the fluid bed. 
     As shown in FIG. 2, several individually controlled lasers  5 , operating in parallel, simultaneously solidify layers of individual custom-moulded ear-plug units or shells in one or more fluid or powder beds  1 . Again, upon completion of this solidification phase and deactivation of the lasers, the powder feed unit  9  deposits a new powder layer, while in the case of laser or stereo lithography the layers just solidified or the already hardened structures are dipped in the fluid bed. 
     As shown in FIG. 3, the laser  5  solidifies the layer S 1  in one powder or fluid bed la, then moves over to bed  1   b  (dotted line) where, during the solidification phase at bed  1   a,  the powder deposition device  9   b  applies powder on a previously solidified layer S 1−  or, in the case of laser or stereo lithography, the layer S 1  is dipped. Not until the laser  5  is activated at bed  1   b  will the powder feed unit  9   a  deposit a new powder layer at bed  1   a  on the layer S 1  just solidified, or will the layer S 1  be dipped in the fluid bed  1   a.    
     When employing the thermojet process, and for correspondingly increased productivity, sectional layers are simultaneously deposited for more than one custom-moulded ear-plug unit or shell, essentially in one single stroke by one applicator head or by several such heads operating in parallel. 
     The process described makes it possible to produce custom-moulded ear-plug units or shells of highly complex shapes both in terms of their outer contours and, in the case of a shell, of its inner contours, with individualized adaptation to the area of application concerned. Ledges, recesses and protrusions can be easily configured. 
     There also exist materials for the incremental build-up process which can be shaped into an elastic yet sturdy shell which latter, if desired, can vary in thickness down to an extremely thin yet break-resistant wall. 
     In a currently preferred implementation the digitizing of the specific individual areas of application, especially those for a hearing aid and in particular for an in-ear hearing aid, is performed at a specialized institution, in the latter case by an audiologist. The individual image information in the form of digital 3D data, especially those for hearing aids, is transmitted to a production center either on a disk or via the Internet. The production center then fabricates the individual custom-moulded ear-plug unit or shell, in the case discussed an in-ear hearing-aid shell, employing in particular the above-mentioned process. The center preferably also performs the complete assembly of the hearing aid with the appropriate functional components. 
     Due to the fact that, as mentioned above, the thermoplastic materials employed generally allow for a relatively elastic outer contour with a snug fit, the problem of pressure points in the shaping of custom-moulded ear-plug units or shells is far less critical than has been the case in the past, a point of particular significance for in-ear custom-moulded ear-plugs. It follows that in-ear custom-moulded ear-plugs such as hearing aids, headphones, water-blocking devices and especially in-ear hearing aids can be inserted much like elastic plugs whose surface adapts itself with a snug fit to the area of application i.e. the auditory meatus or ear canal. One or several venting channels can be easily provided in the in-ear custom-moulded ear-plug unit, ensuring that, notwithstanding the resulting, perhaps relatively tight fit of the custom-moulded ear-plug unit in the ear canal, the air flow to the ear drum remains uninhibited. In the production process, the specific 3D data for the area of application can also be most advantageously employed for optimizing the inner configuration of the plastic unit, even including the accommodation and constellation of any customized components as in the case of a hearing aid. 
     Specifically for custom-moulded ear-plugs in the form of hearing aids, centralized shell production also allows for the centralized storing and management of individual patient data both with regard to the patient-specific area of application and to the individual functional elements and their settings. If for whatever reason a shell must be replaced, it can be reproduced simply by retrieving the individual data sets, without requiring a laborious new fitting as in the past. 
     Given that processes for producing custom-moulded ear-plug devices, albeit prototypes only, have been part of prior art and have been described in earlier literature, there is no need at this juncture to repeat all the technical details of these processes. 
     In any event, it has been surprising to find that adopting these prior-art prototyping technologies yields rather substantial benefits for the industrial, commercially attractive production of custom-moulded ear-plugs, for reasons which for all practical purposes are of no significance in prototyping, such as the elasticity of suitable thermoplastic materials, the ability to customize extremely thin-walled elements, etc. 
     To summarize, employing the above-mentioned additive, incremental build-up process in the production of custom-moulded ear-plug units or shells makes it possible to integrate in these various functional elements, the configuration of which is already laid out in the computer during the design phase of the custom-moulded ear-plug unit and which are installed as the custom-moulded ear-plug unit or shell is produced. In the past, such functional elements were typically retrofitted or added to the finished custom-moulded ear-plug unit or shell, as evidenced by seams at junctions of different or inhomogeneous materials at the points of assembly. 
     For the custom-moulded ear-plugs discussed and especially those containing electronic components, such as hearing aids and especially in-ear hearing aids, the components which can be integrated directly into the custom-moulded ear-plug shell by the technique proposed include, by way of example, the following: Component mounts and holders, cerumen-protection systems, venting channels in the case of in-ear custom-moulded ear-plugs, or channel locks which keep in-ear custom-moulded ear-plugs in place in the auditory canal. 
     FIG. 4 schematically illustrates an example of an in-ear custom-moulded ear-plug unit  11  such as an in-ear hearing aid whose acoustic port  13  on the ear-drum side is provided with a cerumen-protection cap  15 . In past production processes, such a protective cap  15  would be mounted as a separate part on the shell  16  of the custom-moulded ear-plug unit  11  and fastened for instance with glue or by welding. When employing the aforementioned additive build-up process, as shown in an identical illustration in FIG. 5, the cerumen protection cap  15   a  is integrated directly into the shell  16   a  of the otherwise identical in-ear custom-moulded ear-plug unit  11   a.  At the junctions, schematically identified as P in FIG. 4, conventional processes would necessarily lead to material inhomogeneities or seams whereas in the case depicted in FIG. 5 there is no such seam and the material of the shell  16   a  homogeneously transitions into that of the cerumen-protection cap  15   a.    
     This is only one example of how conventional cerumen-protection systems and other functional elements can be directly integrated by employing the abovementioned production process. 
     The following will introduce a few specific, novel custom-moulded ear-plug devices: 
     2. Vented Inner-Ear Custom-moulded ear-plugs 
     It is a conventional practice in the case of in-ear custom-moulded ear-plugs and especially in-ear hearing aids to provide a venting groove on the outer surface, as schematically illustrated in FIG.  6 . As currently used venting grooves go, they are by no means optimized with regard to various features: 
     Acoustic properties: Prior-art venting grooves are not really adapted to the different acoustic requirements. For example, in active custom-moulded ear-plug devices such as in-ear hearing aids they contribute next to nothing to an effective solution of the feedback problem between the electromechanical output converter and the acoustoelectric input converter. In passive in-ear custom-moulded ear-plugs such as ear protectors, they do not provide the desired level of protection while at the same time maintaining good venting properties. 
     Susceptibility to cerumen: The venting grooves currently provided on the outer surfaces of in-ear custom-moulded ear-plugs are extremely susceptible to the formation of cerumen. 
     Depending on its intensity, cerum buildup can quickly limit the air-conducting capacity of the venting grooves by constricting or even fully clogging them. 
     The following describes proposed venting solutions for in-ear custom-moulded ear-plugs and especially for in-ear hearing aids or ear-protection devices, but also for custom-moulded ear-plugs which only partly protrude into the ear canal, such as headphones, which solutions eliminate at least in part the above-mentioned shortcomings of conventional provisions. 
     In this context, one differentiates between venting systems which 
     are essentially in the form of a groove which at least in part opens up toward the wall of the ear canal, 
     are channels completely closed toward the wall of the ear canal. 
     2a) Venting Systems which are Open Toward the Wall of the Ear Canal 
     In FIGS.  7 ( a ) to ( f ), the perspective, schematic partial illustrations of the outer wall  18  of in-ear custom-moulded ear-plugs, resting against the ear canal, depict sections of innovative venting-channel configurations. In FIG.  7 ( a ), the cross section of the venting groove  20   a  is square or rectangular with precisely defined and maintained dimensional parameters. In FIG.  7 ( b ) the venting groove  20   b  has a cross section in the form of a circular or elliptic sector, again with a precisely defined lateral curvature  21   b.  Such precise definition and implementation of the cross-sectional shape of the venting grooves  20  already allows for a certain predictability and control of the acoustic propagation characteristics along the groove when that is in flush contact with the inner wall of the ear canal. Of course, the acoustic properties also depend on the length over which the groove  20  extends along the outer surface  18  of the custom-moulded ear-plug unit. 
     FIGS.  7 ( c ) to ( f ) illustrate other venting-channel cross sections, additionally provided with cerumen protection. The groove per FIG.  7 ( c ) has a T-shaped cross section. 
     In relation to the wide cross-sectional base of the groove in FIG.  27 ( c ), the cantilevering of the sides  23   c  and resultant narrowing  25   c  in the direction of the ear-canal wall already provides an appreciable measure of cerumen protection. Even if cerumen penetrates into the narrow part  25   c  and hardens there, it will not cause any substantial constriction, never mind clogging, of the venting groove, but will only make it an enclosed venting channel. Following the principle explained in relation to FIG.  7 ( c ), FIGS.  7 ( d ) to  7 ( f ) show the wide cross-sectional base  27   d  to  27   f  of the venting groove in various shapes, such as a circular or elliptic sector per FIG.  7 ( d ), triangular as in FIG.  7 ( e ), or circular or elliptical as per FIG.  7 ( f ). 
     A specific, precise design of the cross-sectional surface of the groove, as illustrated by way of only a few examples in FIGS.  7 ( a ) to  7 ( f ), already leads to acoustic as well as cerum-protection properties which are measurably superior to those of conventional, more or less random-shaped venting grooves. For the desired cerumen-protection and acoustic properties, the cross sections are first computer-modeled and then precisely integrated into the custom-moulded ear-plug production units. A particularly suitable way to accomplish this is to employ the additive build-up processes explained above. Further optimization of the acoustic properties of the venting groove can be obtained by providing along these novel venting grooves any given acoustic impedances; in FIG. 8, for example, this results in venting grooves  29  which along their longitudinal direction feature progressively changing cross-sectional shapes, selected and sequenced in FIG. 8 from cross-sections in FIG.  7 . 
     In a manner similar to the design of passive electrical circuitry, the venting groove that is in contact with the ear canal can be computer-modelled and tested for its acoustic transmission properties and then integrated into the in-ear custom-moulded ear-plug device or shell. 
     As illustrated in FIG. 8 at point A, it is possible to specifically provide multiple cerumen-protected sections in correspondingly exposed locations. 
     It may also be altogether desirable especially with a view to optimized acoustic properties to make the venting grooves longer than would normally correspond to the basic length of a given in-ear custom-moulded ear-plug unit. As shown in FIG. 9, this is accomplished by cutting grooves  31  with shapes for instance as illustrated in FIGS. 7 and 8 into the surface of the custom-moulded ear-plug unit along predefined curves, as depicted in the example of FIG. 9, practically in the form of helical grooves surrounding the custom-moulded ear-plug unit. Enhanced, optimal design flexibility is obtained by providing not only one but several venting grooves on the surface of the custom-moulded ear-plug unit, as schematically illustrated in FIG.  10 . This substantial measure of design flexibility makes it possible to configure and variably dimension the venting grooves on the surface of the custom-moulded ear-plug unit so as to optimize cerumen protection and acoustic transmission properties for any particular area of application in the ear canal. 
     2b) Venting Systems with Fully Integrated Channels 
     This design variation of the innovative venting systems consists of venting channels which are at least in some sections fully integrated into the custom-moulded ear-plug unit and closed off against the wall of the ear canal. A system of this type, designed into an custom-moulded ear-plug shell, is described below. However, it should be stressed that, if no further modules need to be integrated in the custom-moulded ear-plug unit discussed and if the latter is a solid plastic body, the following statements naturally also apply to any desired routing of channels through the solid plastic body in question. 
     Analogous to FIG. 7, FIG. 11 illustrates various cross-sectional shapes and surface distribution patterns of the proposed venting channels  33   a  to  33   e.  In FIG.  11 ( a ) the venting channel  33   a  integrated into the custom-moulded ear-plug shell  35   a  has a rectangular or square cross section, in the design version per FIG.  11 ( b ) the cross section of the channel  33   b  is in the form of a circular or elliptic sector. In the design variant per FIG.  11 ( c ) the cross section of the venting channel  33   c  is circular or elliptic while in the design variant per FIG.  11 ( d ) it is triangular. 
     In the embodiment per FIG.  11 ( e ) the custom-moulded ear-plug shell features a complex interior shape, for instance with an integrated retaining-strip extension  37 . For optimal space utilization the cross section of the associated venting channel  35   e  is so designed as to take advantage even of complex shape variations of the custom-moulded ear-plug shell. Accordingly, part of its equally complex cross-sectional form runs into the retaining strip  37  extending from the shell  35   e.    
     Going back to the design variant per chapter 2a) it should be mentioned that this type of complex cross-section which offers optimal utilization of the available space can equally well be chosen for venting grooves that are open toward the wall of the ear canal and, conversely, the channel patterns illustrated in FIGS. 9 and 10 for open grooves can be used for closed venting channels as well. 
     FIG. 12 finally illustrates a design version of a fully integrated venting channel  39  which in its longitudinal direction, for instance in the depicted custom-moulded ear-plug shell  41 , features varying cross sections and/or cross-sectional dimensions so that, with different acoustic impedance elements, the acoustic transmission properties can be optimized. In this context, and with reference to chapter 5) below, it should also be pointed out that the ability to produce complex acoustic impedance characteristics makes it entirely possible to simultaneously utilize at least certain sections of the venting channels, and especially of the closed designs discussed here, as acoustic conductor output sections of active electromechanical converters, like on the output side of microphones, for instance in the case of in-ear hearing aids. 
     Analogous to FIGS. 9 and 10, FIGS. 13 and 14 show how ina given custom-moulded ear-plug unit  43  the integrated venting channels explained in this chapter can be extended by appropriate routing, and, respectively, how two or more of these channels can be integrated into the custom-moulded ear-plug unit, perhaps with different and/or varying channel cross sections analogous to FIG.  12 . 
     These capabilities, described in chapters 2a and 2b and combinable in any desired fashion, open up to the expert innumerable design-variation.opportunities for the novel venting systems and most of all, in view of the various and variously dimensionable parameters, considerable leeway in providing for each individual custom-moulded ear-plug unit optimal cerumen protection as well as optimal acoustic transmission properties. For all design variants the specific individualized system configuration is preferably calculated and computer-modeled for the requirements at hand and the corresponding custom-moulded ear-plug unit custom-fabricated. And again, a particularly suitable way to accomplish this is to employ the production process first above explained, based on the additive building principle known from rapid prototyping and controlled by the optimized modeling data. 
     3. Optimized Structural Stability of Custom-moulded Ear-plug Units 
     This chapter serves to introduce novel custom-moulded ear-plugs which are optimally adapted to the dynamics of the area of application. For example, it is a known fact that, due to their essentially uniform degree of structural stability, conventional custom-moulded ear-plug in-ear devices cannot adapt to the relatively strong dynamic movement of the auditory canal for instance during mastication. Similarly, the acoustic conductors for instance between pinnal i.e. external hearing aids and the auditory canal cannot freely follow a dynamic movement of the area of application. In the case of in-ear custom-moulded ear-plugs, and with ear protectors, earphones, water-repellent ear plugs etc., the same problem is encountered, albeit in part to a lesser degree. Most important, some of their intrinsinc functionality such as their protective effectiveness are compromised the more an allowance is made for the aforementioned dynamics of the area of application. Reference can be made for instance to conventional ear protectors made of an elastically deformable plastic material which, although adapting to the mentioned dynamics of the area of application, do so at the expense of their acoustic transmission characteristics. 
     FIG. 15 shows in schematic fashion a longitudinal section of an in-ear custom-moulded ear-plug device, FIG. 16 schematically illustrates part of the cross section of that same custom-moulded ear-plug unit. The custom-moulded ear-plug unit, for instance designed to accommodate electronic components, includes a shell  45  which, sock-shaped, consists of a thin-walled, elastic material. Where desired, the structural stability of the skin of the shell, smooth on the outside in the design example shown, is assured by means of fins or ribs  47  integrated into the inside of the shell which ribs are of the same material as the skin of the shell. 
     Depending on the necessary dynamic adaptability of the in-ear custom-moulded ear-plug device for instance to match the dynamics of the auditory canal, and on the requirements in terms of channel locks and for protecting built-in components as in the case of an in-ear hearing aid, the progression of the wall thickness of the shell skin  45  and the density and shape of the ribs  47  are computed in advance and the custom-moulded ear-plug unit is built on the basis of the computed data. And again, the above-mentioned production method, employing the additive build-up process, is eminently suitable for the task. Of course, the design of the in-ear custom-moulded ear-plug unit as just explained can without question be combined with a venting system as described with reference to FIGS. 7 to  14 . In particular, for modifying the degree of rigidity i.e. flexibility in specific regions of the custom-moulded ear-plug unit the ribs can have varying cross sections which, if desirable, may also transition progressively along their longitudinal axis from one cross section to another. 
     By way of a perspective illustration, strictly representing one typical example, FIG. 17 schematically shows the outer skin  45  with ribs  47 , the latter displaying varying cross-sectional surface dimensions in the longitudinal direction. 
     In lieu of or in addition to the targeted wall reinforcement and predefined bending and torsional characteristics, in short the structural properties of the in-ear custom-moulded ear-plug unit, the inner ribbing as shown in FIGS. 17 and 18 may be complemented by an outer rib pattern as mentioned further above. To that effect, as indicated in FIGS. 18 and 19, the outer surface of the custom-moulded ear-plug unit  49  is provided with a pattern of ribs  51  which may differ regionally in terms of their density, orientation and cross section. 
     FIG. 19 shows that this approach can be taken with the hollow, cavity-type custom-moulded ear-plugs, but it is equally suitable for custom-moulded ear-plug units without a cavity, for instance without electronic components, and thus for devices such as ear protectors and water-blocking ear plugs. The cross section of an custom-moulded ear-plug unit of this type is schematically shown in FIG.  20 . In this case, the core  53  is made for instance of a highly compressible absorption material, surrounded by a contour-shaping skin  55  with ribbing  57 . The “skin”  55  and the ribbing  57  are produced jointly and integrally, for which once again the production method first above described, employing the additive build-up process, offers itself. To what extent any such additive build-up process will be implementable any time soon when applied to a work piece with inhomogeneous materials, remains to be seen. If that turns out to be possible, the road is clear, for instance in the case of the design example per FIGS. 20, to also build the filler  53  concurrently with the skin  55  and the ribs  57 , layer by sequential layer. 
     Going back especially to FIGS. 18 and 19, it will be evident that the outer rib profiles can also double as delineators for venting channels and/or free spaces, as is illustrated in purely schematic fashion by the example of path P. 
     Referring back once again to FIG. 20, to the dotted line  57 , it is entirely possible, if necessary, to provide the shell skin  55  with an inner rib pattern  57  even when the in-ear custom-moulded ear-plug unit is filled with a filler material and is not intended to accommodate other components such as electronic modules. 
     Moreover, as indicated by the dotted line  59  in FIG. 20, it is possible to produce custom-moulded ear-plug units with a cavity for accommodating modules such as electronic components which cavity  59  is specifically shaped to conform to the size and shape of these additional components to be installed, while at the same time the space between that cavity and the shell skin  55  is filled for instance with a resilient or sound-absorbing material or, alternatively, the components to be installed are embedded in such a material up to the shell skin  55 . 
     The shell skin  55  or, respectively,  45  per FIGS. 15,  16  and  17 , may in fact be produced from an electrically conductive material, creating at the same time an electrical shield for internally situated electronic components. Where appropriate, this also applies to the filler material  53  per FIG.  20 . 
     FIGS. 15 to  20  illustrate an example of an in-ear custom-moulded ear-plug device whose shell is reinforced with inner and/or outer rib profiles, allowing the structure to be exceptionally light-weight and customizable. Obviously, where necessary, this type of structure can also be employed in outer-ear custom-moulded ear-plug units. 
     FIG. 21 shows another design variation of an in-ear custom-moulded ear-plug unit with a specific pliable and, respectively, compressible section. This is accomplished in that the shell  61  of an custom-moulded ear-plug unit, and in particular the shell of an in-ear hearing aid, is provided in one or more predefined areas with a corrugated or bellows-like section  63  which is flexibly expandable or compressible to the necessary extent. Although FIG. 21 illustrates this concept in conjunction with the shell of an in-ear custom-moulded ear-plug device, that concept, where necessary, is entirely implementable in a pinnal custom-moulded ear-plug design as well. Again, the preferred production method is as first above described. 
     In the case of this design example as well it is possible, as explained in reference to FIG. 20, to fill the inner space of the custom-moulded ear-plug unit with the proper filler material for the purpose intended, or to embed integrated modules in such a filler material, thus obtaining improved stability of the device as well as better acoustic properties. 
     4. Modular Housing and Build-ins 
     A problem especially with in-ear hearing aids consists in the fact that the shape of the area of application, i.e. the auditory canal, changes progressively. This is obviously true in the case of youngsters growing up, but even the ear canal of adults changes, often considerably, and mostly in a constrictive sense (e.g. the co-called diver&#39;s ear). 
     Conventional in-ear hearing aids, even where their components could otherwise be expected to be retainable for extended periods in a person&#39;s life, perhaps requiring only a readjustment of the transmission characteristics of the hearing aid in adaptation to the changed auditory conditions, thus pose a problem in that an all-new hearing aid needs to be designed repeatedly merely because the previous ones no longer fit properly into the ear canal. 
     This can already be improved alone by means of the measures explained in the above chapter 3) due to the fact that they permit an automatic adaptation of the shape of the custom-moulded ear-plug unit to the changing area of application. The following will describe additional measures especially for in-ear custom-moulded ear-plug devices. It should be pointed out, however, that for outer-ear custom-moulded ear-plugs as well, such as pinnal hearing aids, it becomes possible to replace the “housing”, and not only when that is necessary for reasons of wearing-comfort but also, if desired, for instance for changing the aesthetic appearance of such an outer-ear hearing aid. 
     FIG. 22 shows schematically the longitudinal section of an in-ear custom-moulded ear-plug unit  65 , whose inner space  67  conforms essentially to the shape of the electronic module  69 , schematically illustrated in FIG. 23, that it must accommodate. The custom-moulded ear-plug unit  65  consists of a rubber-like elastic material and, as shown in FIG. 23, can be slipped over the electronic module  69 . The inner space  67  is so contoured that it matches the shape of any module to be accommodated which is thus held in place by and in the custom-moulded ear-plug unit  65 . In this fashion it is easily possible to equip one and the same electronic module  69  with different custom-moulded ear-plug units  65 , thus permitting an adaptation to the changing shape of the auditory canal for instance of a growing child. Thus, for all practical purposes, the custom-moulded ear-plug unit used for the in-ear hearing aid becomes a replaceable one-way accessory. The custom-moulded ear-plug unit  65  can be easily replaced not only to compensate for changes in the area of application, that being the ear canal, but also when the unit is soiled. This concept may even prove useful, for instance in the case of an ear infection, for introducing medication which could be applied on the outside of the custom-moulded ear-plug unit, or in any event for inserting sterilized custom-moulded ear-plug units at regular time intervals. 
     The concept illustrated in FIGS. 22 and 23 is, of course, combinable with those presented in chapters 2) and 3), and the custom-moulded ear-plug unit  65  is preferably fabricated by the production method explained in chapter 1), which permits the formation of the most complex internal configurations for the tolerance- and vibration-free accommodation of the module  69 . 
     As can be seen in FIGS. 22 and 23, the phase plate  1  with which conventional in-ear hearing aids are equipped, is incorporated as an integral part for instance of the module mount. The same applies to other mounts and retaining cavities for electronic components of the hearing aid. If the incremental layer-by-layer build-up process explained in chapter 1) is applied following the dotted line in FIG. 22 in the direction of the arrow AB, it should be altogether possible to fabricate the custom-moulded ear-plug unit in the progressive build-up direction AB in accordance with the requirements of each area and from a variety of materials. This also applies to the custom-moulded ear-plug devices discussed in chapters 2) and 3) and to those described in the following chapters 5), 6) and 7). In reference to the example per FIG. 22, it is thus entirely possible to fabricate section  65   a  from a rubber-like elastic material and the port section  65   b  from a more rigid material. 
     Depicted in FIG. 24 is another design version of an custom-moulded ear-plug unit, again as an example of an in-ear hearing aid which permits the simple, rapid exchange of the internal, built-in components. It is recommended that for any such in-ear custom-moulded ear-plug unit with built-in components, the shell be produced in several assemblable sections as shown in FIG.  24 . By means of quick-connect closures such as catch pawls, detents or even bayonet-type junctions it is possible to quickly separate the housing sections  73   a  and  73   b  of the in-ear custom-moulded ear-plug unit, remove the internal modules such as electronic components and reinstall these in a new shell, perhaps one with a modified outer contour or into an altogether different shell, as may be necessary for instance for cleaning purposes, sterile requirements etc. In cases where the used shells must be disposed of, it is entirely possible to configure the shell sections in a way that they can be opened only in a destructive fashion, rendering them nonreusable, for instance by means of locking elements such as pawls which are inaccessible from the outside, so that it is necessary to cut the shell open for disposal. 
     Of course, this design version can on its part be combined with the variants described above and those yet to be described below. 
     5. Integration of Acoustic Conductors in Custom-moulded Ear-plug Devices or Their Shells 
     The input and, respectively, output ends of acoustoelectric input converters or electroacoustic output converters in outer-ear as well as in-ear hearing aids are customarily coupled to the auditory environment by way of discrete, separately assembled acoustic conductors in the form of tubular structures, or, especially for acoustoelectric input converters, their receiving surface is positioned in the immediate vicinity of the hearing-aid surface, possibly separated from the environment by only small spaces and protective provisions. 
     The design of hearing aids of that type involves relatively severe restrictions as to where the converter proper and where on the hearing aid the actual interface to the outside world must be positioned. It would be highly desirable to have maximum design latitude in the placement of the interface to the environment and the positioning of the converters within the hearing aid. 
     This is entirely feasible in that the acoustic conductors concerned, extending on the input side from acoustoelectric converters and on the output side from electroacoustic converters, are integrated directly into the custom-moulded ear-plug unit or the wall of the respective custom-moulded ear-plug shell. 
     That is schematically illustrated in FIG. 25. A converter module  75  is provided with an acoustic input or output  77 . Integrated into the shell  79  of the custom-moulded ear-plug unit of an in-ear or pinnal hearing aid or an earphone is an acoustic conductor  81  which, at least in part as shown in FIG. 25, extends within the wall of the custom-moulded ear-plug shell  79 . Preferably, acoustic stub connectors or line sections  83  are employed for tuning the corresponding acoustic impedance of the acoustic conductor  81 . With a view to outer-ear hearing aids, this concept makes it possible to provide input openings  85  wherever desired, in an offset arrangement along the hearing aid, and to couple these via the acoustic conductors  89 , integrated into the custom-moulded ear-plug unit or its shell  87 , to the appropriate acoustoelectric converters  91  essentially regardless of where in the hearing aid these converters  91  are located. As an example only, shown in FIG. 26, two converters are centrally positioned and their inputs are connected to the desired receiving ports  85  via the above-mentioned acoustic conductor  89 . It will be evident from FIGS. 25 and 26 and from the discussion in chapter 2) of the innovative venting systems that it is entirely possible for the venting channels to double as acoustic conductors, especially if, as schematically indicated in FIG. 25, acoustic adapters  83  are used for defining specific acoustic impedance parameters. 
     6. Marking of Custom-moulded Ear-plug Units 
     When custom-moulded ear-plug devices and especially in-ear hearing aids are manufactured, they are customized for each individual wearer. It would therefore be highly desirable to label each such manufactured custom-moulded ear-plug unit, especially each in-ear custom-moulded ear-plug device and most particularly each in-ear hearing aid. Hence, it is recommended that each custom-moulded ear-plug unit or its shell be provided with a recessed or raised labeling area for individualized markings that may include, in addition to the name of the individual buyer, such information as the manufacturer, product serial number, left or right ear application, etc. Most preferably, such labeling is produced during the fabrication of the custom-moulded ear-plug unit by means of the ablation process referred to under 1) above. This ensures that there can be no mix-up with the custom-moulded ear-plug devices. This is particularly important in the subsequent, possibly automated assembly process involving additional modules, for instance in the assembly of in-ear hearing aids. 
     Of course, this step can be combined with any one or several of the procedures described in chapters 2) to 5) above. 
     7. Optimization of Custom-moulded Ear-plug Devices Relative to the Dynamics of the Area of Application 
     For the fitting of custom-moulded ear-plug devices intended for in-ear application, such as in-ear hearing aids, current practice involves the taking of an impression, for instance in silicone, of the auditory canal. Considering the relatively substantial dynamics of movement of the ear canal, for instance during mastication, it becomes obvious that such an impression, a snapshot as it were, can hardly produce a fit of the in-ear custom-moulded ear-plug unit that is entirely satisfactory in everyday use. Therefore, according to the new method as illustrated by the simplified functional/signal-flow diagram in FIG. 27, measurements are taken at several points of statistical dynamic movement in the dynamic application area, represented by the block  93 , i.e. the dynamic movement of the area of application is recorded, frame by frame. The data sets thus obtained are stored in a memory module  95 . With conventional impression-based methodology as well, this approach can be implemented by taking impressions of the area of application at two or more points representative of the actual dynamic movement. 
     These impressions are then scanned and the corresponding digital data sets are stored in the memory  95 . It would also be possible to use x-rays for acquiring the dynamic data of the application area. 
     Accordingly, depending on the intended degree of precision, a number of “frames” or, for all practical purposes, a “film strip” of the movement pattern in the application area of interest is recorded. The data recorded and stored in the memory module  95  are then fed into a computer  97 . The output end of the computer  97  controls the custom-moulded ear-plug production process  99 . If, as is still common practice, the in-ear custom-moulded ear-plugs produced include a relatively hard shell, the computer  97  will use the dynamic data stored in the memory  95 , as well as perhaps other production parameters as schematically indicated at point K, and calculate these for the best fit of the custom-moulded ear-plug unit so as to assure optimal wearing comfort in daily use without compromising functionality. When the custom-moulded ear-plug unit is fabricated following the principle explained in chapter 3), the computer  97  will determine which sections of the custom-moulded ear-plug unit must have what characteristics in terms of flexibility, pliability, compressibility etc. As mentioned above, the output end of the computer  97  controls the production process  99 , and preferably the production process referred to in chapter 1) as the technique of choice.