A HEARING PROTECTOR AND METHOD OF MANUFACTURING THE SAME

Abstract: A hearing protector (1) has a body made of a suitable material and matching the shape of the auricle or ear shell and/or the auditory canal of the user. The body is provided with a canal (2) which, in the condition wherein the body is placed within an ear of the wearer, provides communication between the auditory canal and the free space. The body includes a second canal (3) which, like the first canal, extends between the auditory-canal end and the free-space end of the body. An adjustable damping member (5) is provided in or on the first canal (2) for damping sound to suit the wearer's comfort in conditions in which the device (1) is used.

Description: This invention relates to a hearing protector, comprising a body of a suitable material, the shape of said body being adapted to the shape of the auricle or ear shell and/or auditory canal of the intended wearer of the device, said body being provided with a canal which, in the condition in which the body is placed within an ear of the wearer, provides a communication between the auditory canal and the free space, while moreover means are provided in or on the body for damping the sound transmitted through said canal. The present invention further relates to a method of manufacturing a hearing protector. A hearing protector or otoplast as defined hereinbefore is known from EP-A-0 112 594. The known hearing protector contains a sound damping filter comprising a bore, in which bore an elongate object, for instance a wire, is introduced. Such damps the sound transmitted through the canal. A problem is that once a filter has been placed it can no longer be changed, unless by replacement of the filter or by taking out the filter, replace the wire in the bore, and replace the filter. The known otoplasts are supplied with a standard series of acoustic filters. Depending upon the envisaged use, a filter is determined and an otoplast comprising said filter is supplied. Consequently, hearing protectors are only available with a limited number of damping values or characteristics. Intermediate values can be supplied only upon request, for these have to be manufactured separately. Another problem is that an otoplast placed within the ear can only be measured for checking the leak-tightness of the arrangement, but no longer for determining other properties, such as actual damping and the like. It is an object of the present invention to provide a hearing protector lacking the above drawbacks. This object is achieved with a hearing protector whose body is provided with a second canal which, like the first canal, extends between the auditory-canal end and the free-space end of the body, while the means for damping sound comprise an adjustable damping member in or on the first canal, whereas the second canal is adapted to be connected to a measuring device and is further adapted to be hermetically sealed after adjustment of the damping member is achieved. By virtue of the second canal provided in the otoplast in accordance with the present invention, which canal can be used as a measuring canal, it is possible to effect measurements, with the hearing protector being placed inside the ear. Not only can it thus be established whether there are acoustic leaks, air leaks or otherwise between otoplast and the wall of the auditory canal, but it is also possible to measure whether the damping resistance has the desired value. By further employing an adjustable damping member, the damping resistance can be set accurately at the desired value and this setting can be checked accurately owing to the second canal. It has to be remarked that in EP-A-0 010 168 a device is disclosed comprising a body which is to be placed in the ear of a user, said body being provided with a first canal providing a communication between the auditory canal and the free space. The body furthermore comprises a second canal that branches off from the first canal and therefore extends between the first canal and the free space. The device concerned is a hearing aid. The body with such Y-type canals is used in a method to define the most suitable hearing aid for a certain user. Different types of hearing aids are monitored with help of the body with Y-canal to set a certain level of sound amplification after which the hearing aid providing the most pleasant sound for the particular user is determined. The adjustable damping member of the hearing protector according to the present invention is preferably an infinitely variable reducing valve. Such an acoustic reducing valve may be integral with the hearing protector or be fitted thereon or therein as a separate part. The reducing valve is arranged so as to link up with, or extend into, the first canal and, by means of said valve, the inlet opening can be reduced infinitely until complete closure is achieved. In the latter case, with a device positioned inside the ear of the user, the auditory canal of the user is likewise entirely insulated from the surroundings, owing to the mass of the otoplast placed inside the ear, except that a connection is provided to the surrounding space through the second canal. This connection is broken by connecting a measuring apparatus to the second canal. A superatmospheric pressure can be created in the auditory canal through the measuring apparatus and the second canal, and when the reducing valve is actually fully closed, such superatmospheric pressure can only be maintained if there are no openings between the wall of the otoplast and the wall of the auditory canal. In this way the proper fit of the otoplast in the ear can be checked. After it has been established that a hearing protector according to the present invention properly fits in the ear of the user, and that no air leaks occur, adjustment of the reducing valve can take place, so as to set the desired damping value. This is again measured through the second canal, which is connected to the gauge for the purpose. When all measurements have been effected the second canal can be sealed off in a suitable manner. For the daily use of the hearing protector according to the present invention, the second canal is further no longer required. Yet the presence of the second canal is useful, since in cases where there is a change in the conditions of use, the second canal can be reopened and the reducing valve can be readjusted in the above-described manner to adapt the damping resistance to such changed operating conditions. Naturally, the second canal can always be used for inspection purposes without conditions being changed. The second canal may be a closed canal in that a membrane is incorporated therein. It will be clear that in that case, the above-described measurements should be effected in a slightly different manner. It will be understood that both in case the adjustable damping member of the device according to the present invention is an integral part of the device and in case it is a part to be separately fitted, the damping resistance can be present at an approximate value in the production laboratory, so that upon adjustment of the hearing protector with the user, only a minor correction will be necessary. It has to be remarked that in US-A-3 702 123 an ear mold assembly for use with hearing aids is disclosed, which ear mold assembly includes an acoustical valve with means providing an infinite number of adjustements. In a preferred embodiment of the hearing protector according to the present invention, the infinitely variable reducing valve comprises a needle housing with a needle chamber which tapers from a cylindrical bore in the housing to an oulet opening communicating with the first canal, as well as an adjusting needle, having a cylindrical portion and a conical end extending from the cylindrical portion. Suitably, at the base of the needle chamber, a plurality of radially extending canals provide a communication between the needle chamber and the exterior of the reducing valve extending into the free space. Furthermore, the cylindrical bore may be internally threaded and the adjusting needle attached to a threaded cylindrical foot having means for engagement by a screw driver, wrench or like tool, while preferably, the needle housing is frusto-conical and has the end of the truncated cone having the smaller diameter received in a fitting bore linking up with the first canal in the body of the hearing protector and is fixed in said bore, so that the portion of the needle housing projecting from the body can function as a hand grip. In operating condition, the second canal in the otoplast according to the present invention is hermetically sealed, preferably by a plug inserted into the canal from the free space. Preferably the plug of a device destined for the left ear is visible distinct from the plug of a device destined for the right ear, so that the plug serves as a left/right code. In the above preferred embodiment of the hearing protector according to the present invention, the adjusting needle, which is screwed into the needle housing and has a conical shape to match said housing, fits in said housing in hermetically sealed relationship, when the adjusting needle is entirely screwed home. By screwing back the adjusting needle from this home position, there is formed a space between the needle and the conical inner wall of the needle housing, which space provides a communication between the radial canals and the outlet opening, thereby connecting the auditory canal of the user with the free space outside the otoplast. The size of the passage formed is decisive for the damping resistance or characteristic, which is thus adjustable. Suitable material for the hearing protector according to the present invention are those used for known otoplasts, e.g. synthetic plastics material of the acrylate type. The acoustic reducing valve may consist of synthetic plastics material and the adjusting needle of synthetic plastics material or a material having metallurgical properties. The method according to the present invention for manufacturing the hearing protector according to the present invention is characterized to that effect in that, on the basis of an impression of the auricle or ear shell and/or auditory canal of the intended wearer, a body is made whose shape conforms to the shape of the auricle or ear shell and/or auditory canal of the intended wearer, two acoustically parallel canals are bored in the body, providing communication between the auditory canal end of the body and the free space, a reducing valve is fitted on the free-space end in a bore linking up with the first canal, the body is placed in the ear of the intended wearer and testing and measuring devices are connected to the second canal to check whether the hearing protector can be placed with sufficient leak-tightness and, if necessary, the shape is to be further adapted so as to obtain the desired leak-tightness, and in order to subsequently set the correct damping value by means of the reducing valve, after which, after removal of the body from the ear, the second canal is hermetically sealed off and the setting of the reducing valve is locked, if desired. In the above described manner, an otoplast is made which entirely conforms to the shape of the auditory canal of the intended user. The result is a personal hearing protector the damping of which can be fully adjusted to the working situation of the wearer. One embodiment of the hearing protector according to the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a cross-sectional view of an embodiment of the hearing protector according to the present invention in a condition ready for use; Fig. 2 is a similar view of the hearing protector of Fig. 1 during the testing of the leak-tightness and the setting of the reducing valve; Fig. 3 is a cross-sectional view of the reducing valve of the device shown in Fig. 1; and Fig. 4 is a similar illustration of the reducing valve in "exploded" view. In the figures, like parts are indicated by like reference numerals. The embodiment of the hearing protector according to the present invention shown in Figs. 1 and 2 comprises a body 1 made of a suitable synthetic plastics material, e.g. acrylate. The shape of the body 1 entirely conforms to the shape of the auditory canal of the intended user of the hearing protector. The body 1 is made e.g. by first preparing an impression in wax or like material of the auditory canal of the user and subsequently making from that impression a cast in acrylate. As far as such a cast does not conform fully to the auditory canal yet, it can be further finished by hand. Two canals 2, 3 are provided in the body 1, both forming a communication between, on the one end, the auditory canal end of body 1 (left in Figs. 1 and 2) and on the other , the free-space end of body 1 (right in the figures). The first canal 2 is enlarged at the free-space end, by a bore 4 drilled from that end. The reducing valve 5 is secured in bore 4. Said valve 5, which will be described in more detail with reference to Figs. 3 and 4, is secured in bore 4 e.g. by gluing. Other methods of fixing are of course possible. If desired, the reducing valve 5 may be integral with the body 1. The portion of reducing valve 5 projecting from bore 4 forms a hand grip by means of which the user can position the hearing protector in his ear and remove it. The second canal 3 in the body 1 of the hearing protector according to the present invention is a canal that functions during testing and adjustment of the hearing protector. In the daily use of the otoplast, the second canal 3 has no function any more and, as shown in Fig. 1, it is hermetically sealed off by a plug 26 introduced into canal 3 from the free-space end. The plug is made of a suitable material, e.g. a suitable synthetic plastics material. By imparting to the plug 26 for an otoplast according to the present invention destined for the left ear of the user, a colour differing from that of the plug destined for the otoplast for the right ear, the plug can likewise function as a left/right code. In testing and adjusting the hearing protector according to the present invention a hose 27 of a measuring and regulating appliance (not shown) is connected to the second canal 3, as illustrated in Fig. 2. Hose 27 extends e.g. from the free-space end into an enlarged portion of canal 3. By means of this appliance, when reducing valve 5 is closed a superathmospheric pressure can be generated at the auditory-canal end of body 1 through hose 27 and canal 3, so that it may be checked whether the otoplast fits the auditory canal of the user in a leak-tight manner. If necessary, body 1 can be trimmed to obtain an entirely leak-tight fit. Subsequently, the reducing valve is adjusted and set at the desired damping valve. Figs. 3, 4 show the reducing valve 5 in further detail. Valve 5 comprises a somewhat conically tapering body or needle housing 6, made e.g. of synthetic plastics material and having a central bore 7. In the widest portion of the conical needle housing 6, the bore is cylindrical and has internal threading 8. In the tapering portion of needle housing 6, bore 7 is likewise tapered or conical, terminating in the opening 9 in the front wall of housing 6. At the location where the cylindrical portion of bore 7 merges into the conical portion, four radial canals 10, uniformly interspaced, communicate with the free space. Needle housing 6 accommodates the adjusting needle 11, shown in Fig. 4 removed from housing 6. Needle 11, which is made e.g. of synthetic plastics material or a material having metallurgical properties, comprises a first cylindrical portion 12 whose dimensions correspond with those of the cylindrical portion of bore 7 in needle housing 6. Cylindrical portion 12 is threaded at 13 so that needle 11 can be screwed into housing 6. Adjoining cylindrical portion 12, needle 11 has a reduced cylindrical portion 14, which, in turn, merges into a tapered end portion 15. Cylindrical portion 12 of needle 11 contains two parallel bores 16 extending parallel to, and symmetrically with respect to the axis of needle 11. Bores 16 serve as points of engagement for a special type of wrench or screw driver used for setting the reducing valve. This type of screw driver is not provided at its end with a blade but with two parallel needles fitting in bores 16. Fig 3 shows how needle 11 fits in needle housing 5. As illustrated in Fig. 3 needle 11 has not yet been screwed home. When needle 11 has been screwed home in housing 6, the wall of the conical portion 15 of needle 11 touches the inner wall of the conical portion of bore 7, so that the valve is hermetically sealed. When the needle is slightly screwed back, there is produced a slit 17 between the needle tip 15 and the wall of the bore 7, which slit 17 constitutes a connection between the radical canals 10 and opening 9. By screwing out needle 11 to a greater or lesser extent, the dimensions of slit 17 can be adjusted infinitely. In an embodiment of the hearing protector according to the present invention reduced to practice, the needle housing 5 had a length of 11.0 mm. It was conically formed with a smallest diameter of 4.0 mm and a largest diameter of 6.0 mm. Needle housing 5 contained a bore having at the larger end a cilindrical protion of a diameter of 3.0 mm and a length of 5.0 mm, provided with screw thread M3 with a pitch of 0.25 mm. The connecting portion of the bore tapered conically over a length of 6.0 mm with a largest diameter at the end of the cylindrical portion of 2.0 mm and a smallest diameter at the opening 9 of 0.6 mm. At the transition of the cylindrical portion to the conical portion of the bore, there were provided four radial canals 10, uniformly interspaced, each canal 10 having a diameter of 0.7 mm. The needle 11 fitting in needle housing 5 had a first cylindrical, threaded portion with a pitch of 0.25 mm and a length of 3.0 mm. This portion 12 had such a diameter that it properly fitted in the cylindrical portion of bore 7. To the first portion 12 of needle 11 connected a second cylindrical portion 14, having a diameter of 1.6 mm and a length of 2.5 mm. Next, needle 11 comprised a conically tapering portion 15 with a length of 5.0 mm. Cylindrical portion 12 contained two bores 16 parallel to one another and to the axis of needle 11, having a diameter of 0.5 mm, a depth of 2.0 mm and a pitch measure of 1.0 mm, in which bores fitted a wrench with two cylindrical pins at its end for adjusting the needle in the needle housing. By means of adjusting needle 11, the passage to the auditory-canal side of the reducing valve could be reduced infinitely from a surface area of about 0.283 mm² to a surface area of 0 mm² (entirely closed). One advantage of the hearing protector according to the present invention and the method for its manufacture according to the present invention is that a hearing protection is realized that is entirely tuned to the user, the adjustment and setting of which can take place in vivo.

Claims: Hearing protector comprising a body (1) made of suitable material, the shape of said body (1) conforming to the shape of the auricle or ear shell and/or the auditory canal of the intended wearer of the device, said body (1) being provided with a canal (2) which, in the condition wherein the body (1) is placed within the ear of the wearer, provides a communication between the auditory canal and the free space, while furthermore means (5) are provided in or on the body (1) for damping the sound being transmitted through said canal (2), characterized in that the body (1) is provided with a second canal (3) which, like the first canal (2), extends between the auditory-canal end and the free-space end of the body (1), while the means (5) for damping sound include an adjustable damping member (5) in or on the first canal (2) and in that the second canal (3) is adapted to be connected to a measuring device and is further adapted to be hermetically sealed after adjustment of the damping member (5) is achieved. A hearing protector as claimed in claim 1, characterized in that the adjustable damping member (5) is an infinitely variable reducing valve. A hearing protector as claimed in claim 2, characterized in that the infinitely variable reducing valve (5) comprises a needle housing (6) having a needle chamber that tapers conically from a cylindrical bore (7) in the needle housing (6) to an outlet opening (9) linking up with the first canal (2), as well as an adjusting needle (11) having a cylindrical portion (12,14) and a conical end (15) extending from the cylindrical portion (12,14). A hearing protector as claimed in claim 3, characterized in that at the base of the needle chamber, a plurality of radially extending canals (10) provide communication between the needle chamber and the exterior of the reducing valve extending into the free space. A hearing protector as claimed in either of claims 3-4, characterized in that the cylindrical bore (7) is internally threaded (8) and that the adjusting needle (11) is attached to a threaded cylindrical foot (13) having means (16) for engagement by a screw driver, wrench or the like tool. A hearing protector as claimed in any of claims 3-5, characterized in that the needle housing (6) is frusto-conical and extends with the end of the truncated cone having the smaller diameter into a fitting bore (4) in the body (1) of the hearing protector connecting to the first canal (2) and is secured in said bore (4), so that the portion of the needle housing (6) projecting from the body can function as a hand grip. A hearing protector as claimed in any of claims 1-6, characterized in that the second canal (3) is sealed hermetically by a plug (26) introduced into the canal (3) from the free space. A method of manufacturing the hearing protector as claimed in any of claims 1-7, characterized in that, on the basis of an impression of the auricle and/or auditory canal of the intended wearer, there is made a body (1) whose shape conforms to the shape of the auricle and/or auditory canal of the intended wearer, two acoustically parallel canals (2,3) are bored in the body (1) which provide a communication between the auditory-canal end of the body (1) and the free space, a reducing valve (5) is fitted at the free-space end in a bore (4) connecting to the first canal (2), the body (1) is placed within the ear of the intended wearer and testing and measuring devices are connected to the second canal (3) to check whether the hearing protector can be placed in sufficiently leak-tight condition and, if necessary, the shape is trimmed to obtain the desired leak-tightness, and in order to subsequently set the correct damping value by means of the reducing valve (5), after which the body (1) is removed from the ear, the second canal (3) is hermetically sealed and the setting of the reducing valve (5) is locked, if desired.

Inventors: VAN MIERLO, CORNELIS MATHEUS
Applicants: SAFETEC S.A.
Application year: 1989
Main classification: A61F11
IPC codes: H04R25, A61F11