EP0421233B1 - Device for preventing the penetration of foreign bodies in a sound transducer - Google Patents

Abstract

In an arrangement to prevent the intrusion of foreign matter into a transducer which extends with a projection provided with an opening into a sound channel of a hearing aid, a reduced need for space as well as simpler construction, compared with the state of the art, are achieved by means of the following characterizing features: A membrane made of pore-free material is provided, which has at least one bore for the passage of sound of from a few hundredths to a few tenths of a millimeter diameter, and in which the wall thickness of the membrane is small with respect to the diameter of the bore.

Description

The invention relates to a device against the penetration of foreign bodies, in particular cerumen, into a sound transducer and is based on DE-B-12 63 849.

From DE-B-12 63 849, in an in-the-ear hearing device, a device for preventing the penetration of cerumen (ear wax) into a sound transducer is known, which as a cap-shaped hollow body (ear insert) that can be placed on the sound outlet connector (attachment) of a hearing device. is made of elastic material, which has in its interior a chamber-like extension of a sound passage bore at its hemispherical end, in which a layer of porous, sound-permeable material is arranged. With a pore size of about 0.2 to 0.5 mm and relatively thin partition walls to achieve a large pore density per unit area, the porous layer has a relatively large thickness, which approximately corresponds to the inner cylinder radius of the hollow body. The wall thickness of the hollow body is approximately one seventh of the outer diameter of the cylinder. It is therefore relatively thick. Overall, this device requires a large amount of space, particularly in the direction of sound transmission. In addition, two separate components are required to close the sound outlet connector against the penetration of cerumen, the hollow body acting as a holder (additional device) for the porous layer, which in turn prevents the penetration of cerumen and must be renewed regularly, since this porous and therefore cleaning soft material is not possible.

From DE-U-84 36 783 and DE-U-85 04 765 sieve-like perforated caps are known which can be screwed or plugged into or onto approaches are that protrude from the hearing aid housing for this purpose only as an extended sound channel. The penetration of cerumen into the sound channel is largely prevented due to the formation of niches (trenches) on the housing outside the sound channel. The outer approach, which is only necessary for holding the perforated caps, is an additional device and requires a relatively large overall length in the direction of sound propagation, which is further increased by the wall thickness of the perforated caps protruding from the approaches, in particular because their wall thickness is approximately of the order of magnitude sieve-like holes. In addition, the large number of holes arranged in a sieve increases the risk of cerumen penetration.

The object of the present invention is to design a device of the type mentioned at the outset in such a way that, with a reduced space requirement, the structure is simple compared to the prior art.

This object is achieved by the features specified in claim 1.

The following essential advantages are achieved with the invention: An additional device - as a separate cap-shaped hollow body as a holder for an inner porous layer (membrane, diaphragm) or an extension which protrudes from the hearing device housing as an extended sound channel - is unnecessary because the inventive one Device also uses an approach, which is necessary anyway for other purposes, on a sound transducer (for example a receiver) as a holder for a membrane. Reduced space requirements, particularly in the direction of sound propagation (short overall length), are created by arranging the membrane according to the invention in the sound channel which is necessary anyway. According to the invention, the term "membrane" means a component that is thin, film-like, sound-permeable and perforated-like. The arrangement of the membrane on a projection of a hearing aid component protruding into the sound channel was made possible by using non-porous Material (higher strength) - for which metallic materials are particularly suitable - with extremely thin walls (foil-like). Measurements on the occasion of the invention surprisingly showed that with a film-like small wall thickness of the membrane according to the invention, a sound passage bore (for example made with a laser beam) with a diameter on the order of pores on known thick membranes, preferably up to about 0.6 mm, is sufficient To allow largely undisturbed sound passage (low linear attenuation) on the membrane.

If the diameter of the sound passage bore on the film-like thin membrane according to the invention is reduced to a few tenths of a millimeter, preferably to about 0.15 mm, surprisingly, the device according to the invention has a clearly non-linear influence on the acoustics with the effect that with linearly increasing Output level of the sound source creates a non-linearly increasing decrease (attenuation) of the sound permeability on the membrane according to the invention. Measurements and tests on the occasion of the invention have shown that with this further novel effect of the device according to the invention, the effect of an electrical output level limiting circuit (peak clipping, PC) and / or an automatic gain control (AGC) can be largely simulated. With the device according to the invention it is therefore also possible to achieve the essential advantage that an electrical device for non-linear sound level attenuation which was previously required in the hearing device is dispensed with, which at the same time reduces the space requirement in the hearing device.

Further advantages and details of the invention emerge from the following description of an exemplary embodiment with reference to the drawings and in conjunction with the further claims.

• Figur 1 ein In-dem-Ohr-Hörgerät mit teilweise schnittbildlicher Darstellung des Gehäuses mit einer erfindungsgemäßen Vorrichtung und
• Figuren 2 bis 4 Dämpfungsverläufe von Schallpegeln mit verschiedenen Parametern.

Show it:

• 1 shows an in-the-ear hearing aid with a partially sectional representation of the housing with a device according to the invention and
• Figures 2 to 4 attenuation curves of sound levels with different parameters.

The in-the-ear hearing aid according to FIG. 1 has a housing 1, in which, among other things, parts essential to the invention are shown. A sound channel 4 extends between an outer end face 2 and an inner end face 3 of the housing 1. A receiver 5 projects into the sound channel 4 with its extension 7 having an opening 6, on which a membrane 8 made of non-porous, metallic material is arranged , which has a sound passage bore 9. The diameter of the sound passage bore 9 is only a few tenths of a millimeter. It is crucial that the wall thickness of the membrane 8 is chosen to be small compared to the diameter of the sound passage bore 9. A size ratio of approximately 1:10 results in a good sound transmission effect with a wall thickness of approximately 2/100 millimeters.

The membrane 8 is cap-shaped and made of a deep-drawn material, for example mumetal, as a deep-drawn part. In spite of the small wall thickness, good mechanical stability is thereby achieved, in particular with respect to mechanical cleaning (scraping off) of cerumen, for example with a wire loop. The membrane 8 has a cylindrical region 10 and a region 11 which is curved further therefrom. The curved area 11 increases the mechanical stability of the membrane 8 and the cylindrical area 10 enables simple clamping attachment to the usually cylindrical extension 7 of the sound transducer, which is shown here as the receiver 5. The approach 7 has a diameter of about 1.4 mm and a length of about 1 mm. The membrane 8 is completely within of the sound channel 4 is arranged, whereby in connection with the curved area 11 an annular recess 12 is formed within the sound channel 4. Cerumen can accumulate in this annular recess 12, which makes a separate trench formed on the housing 1 unnecessary for the accumulation of cerumen.

The neck 7 on the receiver 5 is with the membrane 8 attached thereto in a sleeve 13 made of sound-absorbing material, e.g. a silicone tube, held in the housing 1 by means of a snap connection 14 and is also designed as a sound channel. The inner diameter of the sound channel 4 corresponds approximately to the diameter of the extension 7. With a low elasticity of the sound channel 4, the inner diameter of the sound channel 4 can be chosen larger up to twice the wall thickness of the membrane 8. A recessed arrangement of the sleeve 13 (the overall length is chosen to be shorter than the distance between the outer end face 2 and the inner end face 3 of the housing 1) creates a further annular recess 15 on the outer end face 2 of the housing, in which cerumen also accumulates can. The result is a very long path for the cerumen before it can reach the sound passage bore 9 arranged in the center of the curved area 11 of the membrane 8. This creates large time intervals between the mechanical and thus inexpensive and easy to carry out cleaning of the device.

Due to the small wall thickness of the membrane 8, it is also possible to arrange it within (not shown) the opening 6 of the extension 7 of the sound transducer shown here as the receiver 5, which also prevents the penetration of foreign bodies, in particular cerumen, into the respective sound transducer.

Since an electrical non-linear sound level influencing can largely be simulated with the invention, is suitable the device is particularly suitable for use in conjunction with a sound transducer designed as a microphone, which is not shown. On the one hand, foreign bodies that are larger than the diameter of the opening 6 of the membrane 8 can be kept away from the microphone. On the other hand, additional devices, such as electrical level limiting circuits (PC, AGC), are also unnecessary and there is no overriding of the electrical hearing aid amplifier the resulting side effects can be avoided.

The achievable extent of the non-linear influence on the acoustics with the device according to the invention as a function of the level of a sound source and the diameter of the sound outlet opening in a membrane according to the invention is exemplified in FIGS. 2 to 4 on the basis of curves 16 to 22 and 16 ′ to 22 'Shown. To simplify the interpretation of the measurement results, the wall thickness of the membrane was uniformly set at 0.02 mm in the recorded curves 16 'to 22' and a membrane made of mumetal in the deep-drawing process was always used. All curves were measured on a hearing aid on which a handset was operated with constant current.

• Durchmesser der Schalldurchtrittsöffnung in der Membran 0,4 mm,
• Wandstärke der Membran 0,02 mm,
• maximaler Ausgangspegel am Hörer von 110 dB bei Kurve 16 ohne und bei Kurve 16′ mit Membran;

Figur 2 zeigt deutlich, daß bei einem Durchmesser der Schalldurchtrittsöffnung von 0,4 mm und einem maximalen Ausgangspegel von 110 dB gemäß Kurve 16 nur bei diesem hohen Ausgangspegel eine Dämpfung gegenüber Kurve 16′ von ca. 3 dB eintritt. Bei den niedrigen Ausgangspegeln außerhalb des Frequenzbereiches um 2 kHz ist der Dämpfungsunterschied deutlich geringer oder gar nicht mehr vorhanden.The following parameters apply to FIG. 2:

• Diameter of the sound passage opening in the membrane 0.4 mm,
• Wall thickness of the membrane 0.02 mm,
• maximum output level at the listener of 110 dB for curve 16 without and for curve 16 'with membrane;

Figure 2 clearly shows that with a diameter of the sound passage opening of 0.4 mm and a maximum output level of 110 dB according to curve 16, attenuation compared to curve 16 'of approximately 3 dB occurs only at this high output level. At the low output levels outside the frequency range around 2 kHz the attenuation difference is significantly smaller or no longer available.

• Durchmesser der Schalldurchtrittsöffnung in der Membran 0,25 mm,
• Wandstärke der Membran 0,02 mm,
• maximaler Ausgangspegel am Hörer von 110 dB bei Kurve 17 ohne und bei Kurve 17′ mit Membran,
• maximaler Ausgangspegel am Hörer von 100 dB bei Kurve 18 ohne und bei Kurve 18′ mit Membran,
• maximaler Ausgangspegel am Hörer von 90 dB bei Kurve 19 ohne und bei Kurve 19′ mit Membran;

In Figur 3 wurden die strichlierten Kurven 17′ bis 19′ bei einem Durchmesser der Schalldurchtrittsöffnung an der Membran von 0,25 mm aufgenommen. Zwischen den beiden Kurven 17 und 17′ entsteht jetzt eine maximale Pegeldifferenz von ca. 7 dB bei wiederum maximalen Ausgangspegel von 110 dB. Bei einem maximalen Ausgangspegel von 100 dB entsteht zwischen den Kurven 18 und 18′ eine maximale Differenz von nur etwa 4 dB. Zwischen Kurve 19 mit einem maximalen Ausgangspegel von 90 dB beträgt die Differenz zur Kurze 19′ nur noch etwa 3 dB. Daraus ist deutlich erkennbar, daß die Dämpfung durch die erfindungsgemäße Vorrichtung mit zunehmenden Ausgangspegel nichtlinear zunimmt. Außerdem nimmt die Dämpfung mit sinkendem Durchmesser der Schalldurchtrittsöffnung zu, was ein Vergleich der Kurven 16 und 16′ in Figur 2 mit den Kurven 17 und 17′ in Figur 3 deutlich macht.The following parameters apply to FIG. 3:

• Diameter of the sound passage opening in the membrane 0.25 mm,
• Wall thickness of the membrane 0.02 mm,
• maximum output level at the listener of 110 dB with curve 17 without and with curve 17 ′ with membrane,
• maximum output level at the listener of 100 dB with curve 18 without and with curve 18 ′ with membrane,
• maximum output level at the listener of 90 dB with curve 19 without and with curve 19 'with membrane;

In Figure 3, the dashed curves 17 'to 19' were recorded at a diameter of the sound passage opening on the membrane of 0.25 mm. Between the two curves 17 and 17 'there is now a maximum level difference of approximately 7 dB with a maximum output level of 110 dB. At a maximum output level of 100 dB, there is a maximum difference of only about 4 dB between curves 18 and 18 '. Between curve 19 with a maximum output level of 90 dB, the difference to the short 19 'is only about 3 dB. From this it can be clearly seen that the attenuation by the device according to the invention increases non-linearly with increasing output level. In addition, the damping increases with decreasing diameter of the sound passage opening, which makes a comparison of the curves 16 and 16 'in Figure 2 with the curves 17 and 17' in Figure 3 clearly.

• Durchmesser der Schalldurchtrittsöffnung in der Membran 0,15 mm,
• Wandstärke der Membran 0,02 mm,
• maximaler Ausgangspegel am Hörer von 110 dB bei Kurve 20 ohne und bei Kurve 20′ mit Membran,
• maximaler Ausgangspegel am Hörer von 100 dB bei Kurve 21 ohne und bei Kurve 21′ mit Membran,
• maximaler Ausgangspegel am Hörer von 90 dB bei Kurve 22 ohne und bei Kurve 22′ mit Membran.

The following parameters apply to FIG. 4:

• Diameter of the sound passage opening in the membrane 0.15 mm,
• Wall thickness of the membrane 0.02 mm,
• maximum output level at the listener of 110 dB with curve 20 without and with curve 20 ′ with membrane,
• maximum output level at the listener of 100 dB with curve 21 without and with curve 21 ′ with membrane,
• maximum output level at the listener of 90 dB with curve 22 without and with curve 22 'with membrane.

In Figure 4, the relationships described are more clearly visible because the diameter of the sound passage opening on the membrane has been reduced to 0.15 mm. Compared to curve 20 with a maximum sound output level of 110 dB to curve 20 ', which was recorded with a membrane according to the invention, an attenuation of approximately 17 dB. In addition, with this diameter reduction on the membrane, an almost linear frequency response was achieved in the transmission range of the listener. At a reduced output level, the attenuation in turn decreases non-linearly, which is based on curves 21 and 21 'with a maximum level difference of 14 dB and on curves 22 and 22' with a maximum level difference of only about 11 dB at a maximum output level of 90 dB can be seen.

Claims (10)

1. Device for preventing penetration of foreign bodies into a sound transducer, which transducer, with a projection (7) having an opening (6), extends into a sound channel (4) of a hearing aid, characterised by a membrane (8) produced from a pore-free material, which membrane has at least one bore for the passage of sound (9) with a diameter of 0.09 to 0.6 millimetres, and in which device the wall thickness of the membrane is smaller than the diameter of the bore for the passage of sound.
2. Device according to claim 1, in which the bore for the passage of sound (9) of the membrane (8) has a diameter of 0.15 mm to 0.4 mm for non-linear control of the acoustic level of the sound passing through.
3. Device according to claim 1 or 2, in which the membrane (8) is formed like a cap of a metallic and particularly deep-drawable material, preferably mu-metal.
4. Device according to one of claims 1 to 3, in which the membrane (8) is arranged completely inside the sound channel (4), the diameter of which channel corresponds approximately to the outer diameter of the projection (7) or is selected to be larger by up to twice the wall thickness of the membrane.
5. Device according to one of claims 1 to 4, in which the wall thickness of the membrane (8) is a maximum of a few hundredths of a millimetre, preferably approximately 0.02 mm.
6. Device according to one of claims 1 to 5, in which the membrane (8) has a cylindrical (10) region and a curved region (11) pointing away therefrom.
7. Device according to claim 6, in which the membrane (8) is secured with its cylindrical region in a clamping manner on the cylindrical projection (7).
8. Device according to claim 6 or 7, in which the membrane (8) is held with the projection (7) in a tube or in a sleeve (13), which are formed in each case as a sound channel, into which extends the projection (7).
9. Device according to claim 6, in which the membrane (8) has the bore for the passage of sound (9) in the centre of the curved region (11).
10. Device according to one of claims 1 to 9, in which the membrane (8) is arranged inside the projection (7) of the sound transducer, in particular of the earphone (5).

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