Damping filter for a hearing device

Abstract

The present disclosure relates to a hearing device having a microphone, where most of the microphone is shielded by an outer shielding of the hearing device. An inlet in the outer shielding allows sound from outside the hearing aid to travel to the microphone to be picked up by it. However, the combination of the microphone and the inlet results in the microphone becoming more sensitive at some audible frequencies. A damping filter positioned in connection with the inlet acts to counter the acoustic effect of the inlet by damping sound in the audible frequency range, where the microphone has increased sensitivity.

Claims

1. A hearing device comprising: a microphone; a shielding, the shielding comprising a channel configured to conduct sound from outside of the hearing device, the channel having an outer opening through which the sound from the outside can enter, and an inner opening for outputting the sound; and a damping filter positioned in connection with the channel such that the sound being conducted by the channel can pass through the damping filter, wherein the damping filter is configured to acoustically dampen the sound before the sound arrives at the microphone, so as to at least partially counteract an increased sensitivity of the microphone at audible frequencies due to acoustic effect of the channel; wherein the damping filter is configured to provide a sound damping that is at least 1 dB at a frequency below 20 kHz.

2. The hearing device according to claim 1, wherein the damping filter extends entirely or at least partially across the channel.

3. The hearing device according to claim 1, wherein the damping filter is associated with one or more filter parameters, the one or more filter parameters being an effective filter area, a pore size, a filter thickness, a distance from the microphone, or any combination of the foregoing.

4. The hearing device according to claim 1, wherein the damping filter has an effective filter area that is anywhere from 0.1 mm.sup.2-13 mm.sup.2.

5. The hearing device according to claim 1, wherein the damping filter has an effective filter area that is anywhere from 0.19 mm.sup.2-3.15 mm.sup.2.

6. The hearing device according to claim 1, wherein the damping filter has an effective filter area that is anywhere from 0.19 mm.sup.2-1.77 mm.sup.2.

7. The hearing device according to claim 1, wherein the damping filter has a pore with a pore size that is anywhere from 5 mu-25 mu.

8. The hearing device according to claim 1, wherein the damping filter has a filter thickness that is anywhere from 5 mu-2500 mu.

9. The hearing device according to claim 1, wherein the damping filter has a filter thickness that is anywhere from 20 mu-200 mu.

10. The hearing device according to claim 1, wherein the the frequency is anywhere from 3 kHz-20 kHz.

11. The hearing device according to claim 1, wherein the damping filter is configured to provide the sound damping that is at least 2 dB at the frequency below 20 kHz.

12. The hearing device according to claim 1, wherein the damping filter is configured to provide the sound damping that is at least 5 dB at the frequency below 20 kHz.

13. The hearing device according to claim 1, wherein the shielding comprising the channel extends in a primary direction that is non-parallel to a longitudinal axis of the channel.

14. The hearing device according to claim 1, wherein the damping filter is configured to also provide a sound damping at an ultrasound frequency.

15. A hearing device comprising: a microphone; a shielding, the shielding comprising a channel configured to conduct sound from outside of the hearing device, the channel having an outer opening through which the sound from the outside can enter, and an inner opening for outputting the sound to the microphone; and a damping filter positioned in connection with the channel such that the sound being conducted by the channel can pass through the damping filter, wherein the damping filter is configured to acoustically dampen the sound before the sound arrives at the microphone, so as to at least partially counteract an increased sensitivity of the microphone at audible frequencies due to acoustic effect of the channel; wherein the damping filter is within the channel between the inner opening and the outer opening.

16. A hearing device comprising: a microphone; a shielding, the shielding comprising a channel configured to conduct sound from outside of the hearing device, the channel having an outer opening through which the sound from the outside can enter, and an inner opening for outputting the sound; and a damping filter positioned in connection with the channel such that the sound being conducted by the channel can pass through the damping filter, wherein the damping filter is configured to acoustically dampen the sound before the sound arrives at the microphone, so as to at least partially counteract an increased sensitivity of the microphone at audible frequencies due to acoustic effect of the channel; wherein the shielding is configured to shield the microphone and one or more components in the hearing device.

17. A method performed by a hearing device, the hearing device comprising a microphone, and a shielding, the shielding comprising a channel, the channel having an outer opening and an inner opening, the method comprising: receiving sound by the outer opening of the channel; conducting the sound by the channel; outputting the sound via the inner opening of the channel; and acoustically dampening the sound by a damping filter before the sound arrives at the microphone, so as to at least partially counteract an increased sensitivity of the microphone at audible frequencies due to an acoustic effect of the channel; wherein the damping filter is configured to provide a sound damping that is at least 1 dB at a frequency below 20 kHz.

18. The method according to claim 17, wherein the damping filter extends entirely or at least partially across the channel.

19. The method according to claim 17, wherein the damping filter is associated with one or more filter parameters, the one or more filter parameters being an effective filter area, a pore size, a filter thickness, a distance from the microphone, or any combination of the foregoing.

20. The method according to claim 17, wherein the frequency is anywhere from 3 kHz-20 kHz.

21. The method according to claim 17, wherein the damping filter is configured to provide the sound damping that is at least 2 dB at the frequency below 20 kHz.

22. The method according to claim 17, wherein the damping filter is configured to provide the sound damping that is at least 5 dB at the frequency below 20 kHz.

23. The method according to claim 17, wherein the damping filter is configured to also provide a sound damping at an ultrasound frequency.

24. A method performed by a hearing device, the hearing device comprising a microphone, and a shielding, the shielding comprising a channel, the channel having an outer opening and an inner opening, the method comprising: receiving sound by the outer opening of the channel; conducting the sound by the channel; outputting the sound via the inner opening of the channel to the microphone; and acoustically dampening the sound by a damping filter before the sound arrives at the microphone, so as to at least partially counteract an increased sensitivity of the microphone at audible frequencies due to an acoustic effect of the channel; wherein the damping filter is within the channel between the inner opening and outer opening.

25. A hearing device comprising: a microphone; a shielding, the shielding comprising a channel configured to conduct sound from outside of the hearing device, the channel having an outer opening through which the sound from the outside can enter, and an inner opening for outputting the sound; and a damping filter positioned in connection with the channel such that the sound being conducted by the channel can pass through the damping filter, wherein the damping filter is configured to acoustically dampen the sound before the sound arrives at the microphone, so as to at least partially counteract an increased sensitivity of the microphone at audible frequencies due to acoustic effect of the channel; wherein the damping filter is configured to provide a sound damping at a frequency that is between 6 kHz-20 kHz.

26. The hearing device according to claim 25, wherein the sound damping is at least 1 dB.

27. The hearing device according to claim 25, wherein the sound damping is at least 2 dB.

28. The hearing device according to claim 25, wherein the sound damping is at least 5 dB.

29. The hearing device according to claim 25, wherein the shielding comprising the channel extends in a primary direction that is non-parallel to a longitudinal axis of the channel.

30. The hearing device according to claim 25, wherein the damping filter is configured to also provide a sound damping at a frequency that is between 3 kHz-6 kHz.

31. The hearing device according to claim 25, wherein the damping filter is configured to also provide a sound damping at an ultrasound frequency.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following exemplary embodiments are described in more detail with reference to the appended drawings, wherein:

(2) FIG. 1 shows a simplified drawing of an exemplary hearing aid having a microphone inlet,

(3) FIG. 2 shows a graph of the simulated frequency response of a microphone for a hearing device when affected by the acoustic effect of an inlet,

(4) FIG. 3 shows a simplified drawing of a microphone for a hearing device behind an outer shielding having an inlet with a damping filter according to an embodiment,

(5) FIGS. 4A, 4B and 4C are simplified drawings of a damping filter positioned within an inlet channel according to some embodiments,

(6) FIG. 5 shows a graph of simulated and measured frequency response at audible frequencies of a microphone for a hearing device with and without a damping filter,

(7) FIG. 6 shows a graph of the measured frequency response at ultrasound frequencies of a microphone for a hearing device with and without a damping filter, and

(8) FIG. 7 shows a flow diagram in accordance with exemplary embodiments.

DETAILED DESCRIPTION

(9) Various exemplary embodiments and details are described hereinafter, with reference to the figures when relevant. It should be noted that the figures may or may not be drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. Like elements will, thus, not necessarily be described in detail with respect to each figure. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or if not so explicitly described.

(10) FIG. 1 shows a simplified drawing of a hearing device 1 exemplified as a behind-the-ear part of a receiver-in-ear hearing aid 1. The hearing aid 1 has a microphone (not visible), which is shielded by an outer shielding 5 from mechanical damage and harmful substances. The outer shielding 5 has an inlet with an outer opening 7. The inlet conducts sound from the environment outside of the hearing aid 1 to the microphone within the outer shielding 5 of the hearing aid 1. The presence of the inlet conducting sound to the microphone has an acoustic effect such that the combined system of the inlet and the microphone effectively makes the microphone more sensitive to some frequencies of sound.

(11) FIG. 2 shows a graph of the simulated frequency response of a microphone. Microphones, which are different models, and particularly, different types will have a dissimilar frequency response. When the microphone is positioned with an inlet, the frequency response is altered as shown in the graph. When affected by the acoustic effect of an inlet this particular microphone displays an undesirable increased sensitivity to sound at frequencies above approximately 6 kHz.

(12) FIG. 3 shows a simplified drawing of a microphone 3 positioned behind an outer shielding 5 having an inlet comprising an outer opening 7, an inner opening 9 and an inlet channel 11 extending between the inner opening 9 and the outer opening 7. The inlet conducts sound from outside the outer shielding 5 via the inlet channel 11 to the microphone 3.

(13) The presence of the inlet affects the frequency response of the microphone 3 as illustrated by the graph in FIG. 2. The inlet therefore further comprises a damping filter 13, which is positioned within the inlet channel 11 and which is configured to counteract the acoustic effect of the inlet, which is an increased sensitivity of the microphone at audible frequencies. This is achieved by the damping filter 13 acting as an acoustic damper. Some of the parameters, which affect the damping produced by the damping filter 13, are effective filter area, pore size, filter thickness and distance of the filter 13 from the microphone 3.

(14) The damping filter 13 is installed in the inlet channel 11 as a filter extending beyond the cross-section of the inlet channel 11. This is an example of how the damping filter 13 can be installed during assembly of the hearing device 1. The part of the filter, which extends into the outer shielding 5 does not form part of the effective filter area of the damping filter 13. The damping filter 13 may be installed in other ways known to the skilled person.

(15) A damping filter 13 will preferably extend entirely across the inlet channel 11 such that the sound being conducted by the inlet has to pass through the damping filter 13. However, the damping filter 13 may extend only partially across the inlet channel 11 and still serve it's function, i.e. without the damping of the damping filter 13 being compromised to an unacceptable degree.

(16) The damping filter 13 is simplistically illustrated in FIG. 3 as positioned at a right angle across a simple inlet channel 11 without varying cross-section. However, the damping filter 13 may be positioned at an angle with respect to the wall of the inlet channel 11. Also, the inlet channel 11 may have a varying cross-section. Further, the damping filter 13 may comprise more than one filter, where a resultant acoustic damping is achieved by the plurality of individual filters comprised in the damping filter 13.

(17) FIGS. 4A, 4B and 4C show simplified drawings of a damping filter 13 comprising a plurality of individual filters 15 positioned within an inlet channel 11 according to some embodiments. The individual filters 15 may be separated by space, wherein no filter material is present or be positioned abutting each other. If the individual filters 15 have similar properties, abutting them will acoustically resemble a single filter of the total thickness of the abutting filters. However, the individual filters 15 may have dissimilar properties such as different pore sizes, effective filter areas and filter thicknesses. The individual filters 15 may also be made of different materials.

(18) In FIG. 4A is shown a damping filter 13 comprised of two individual filters 15 separated by a space, wherein no filter material is present. The two filters 15 are positioned at right angles to the wall of the inlet channel 11, which has a constant cross-section.

(19) FIG. 4B shows a damping filter 13 comprised of two individual filters 15, where one of the two filters 15 are positioned at a right angle to the wall of the inlet channel 11, while the other of the individual filters 15 is positioned within the inlet channel 11 at an angle that is not 90 degrees with respect to the inlet channel wall.

(20) FIG. 4C illustrates a damping filter 13 comprised of two individual filter 15, where both filters 15 are positioned within the inlet channel 11 at angles that are not 90 degrees with respect to the inlet channel wall.

(21) FIG. 5 shows a graph of the simulated and measured frequency response at audible frequencies of a microphone for a hearing device installed with an inlet to conduct sound to the microphone. When no damping filter is installed a relatively large peak is seen at the high frequency end of the audible spectrum (compare with FIG. 2). The unfiltered frequency response with a large peak is undesirable, but can be mitigated by installing a damping filter in connection with the inlet. The damping filter is configured to dampen the sound in the range, where the presence of the inlet causes increased sensitivity of the microphone. The effect is to dampen the peak, which will make the graph of the frequency response “flatter”, i.e. with a smaller range of level values, which is desirable in hearing devices. As shown in FIG. 5, the effect of the damping filter can be significant.

(22) As the peak will usually be in the higher range, such as e.g. 3-20 kHz, of the audible frequencies for hearing device microphone inlets, such as a hearing aid microphone inlet, the damping filter is designed to dampen in this range of audible frequencies.

(23) The microphone model shown in FIG. 5 was successfully dampened more than 7 dB at the frequency of the peak maximum.

(24) FIG. 6 shows a graph of the measured frequency response at ultrasound frequencies of a microphone for a hearing device installed with an inlet to conduct sound to the microphone. As an additional benefit of the damping filter, when damping at high frequencies in the audible spectrum, is that it will likely also dampen at ultrasound frequencies. In FIG. 6 can be seen damping by a damping filter of at least 1-2 dB and even more than 4 dB at frequencies in the ultrasound spectrum. Damping of ultrasound in hearing devices is desirable, as the ultrasound can can saturate microphones and create problems in the delicate sensors and electronics of the hearing device.

(25) FIG. 7 shows a flow diagram in accordance with exemplary embodiments. The flow diagram illustrates a method of configuring a hearing device, wherein a damping filter is used in connection with a microphone inlet to counteract the acoustic effect of the inlet on the frequency response of the microphone. The damping filter may e.g. be any of the embodiments described herein.

(26) The hearing device comprises a microphone, and an outer shielding, which is configured to shield components within the device. The outer shielding comprises an inlet channel configured to conduct sound from the outside of the device to the microphone. The inlet channel has an outer opening through which sound from the outside enters and an inner opening through which sound arrives at the microphone.

(27) In step S10, the frequency response of the microphone is simulated or measured under the acoustic effect of the inlet channel.

(28) In step S20, a damping filter is configured such that, when installed, the damping filter will acoustically dampen the sound arriving at the microphone via the inlet channel so as to at least partially counteract the increased sensitivity of the microphone at audible frequencies due to the acoustic effect of the inlet channel,

(29) The system comprising a microphone and an inlet may be simulated with the inlet simulated as a transmission line of optionally varying diameter and the damping filter modelled as simple resistance. The resistance will then be proportional to the effective filter area of the damping filter such that the effective filter area can be tuned in simulation by tuning the resistance. This assumption is valid in the audio band, whereas at ultrasonic frequencies the damping filter may start behaving as a membrane.

(30) As the filter introduces noise, the filter configuration may be an optimization of the trade-off between the damping and the noise created by the damping filter.

(31) One or more parameters may be fixed, for example the pore size of the damping filter could be fixed and from the simulation an effective filter area can be determined to reach a desired damping.

(32) In step S30, the damping filter is positioned in connection with the inlet channel between the inner opening and outer opening.

LIST OF REFERENCES

(33) 1 Hearing device 3 Microphone 5 Outer shielding 7 Outer opening 9 Inner opening 11 Inlet channel 13 Damping filter 15 Individual filter comprised in damping filter