EP2276272B1 - Hearing aid and method for suppressing feedback - Google Patents

Abstract

The apparatus i.e. hearing aid (1), has a microphone (2) emitting a microphone signal (11). A receiver (4) picks up a receiver signal (12). Static compensation filters (51) form compensation signals (151) from the receiver signal. A selection unit (8) selects and subtracts the compensation signals from the microphone signal such that a feedback signal caused by feedback is minimal in the receiver signal. The filters model different acoustic feedback paths and include filter coefficients to be determined by feedback path measurements. An independent claim is also included for a method for suppressing feedback in a hearing apparatus.

Description

The invention relates to a specified in claim 1 hearing aid for suppressing feedback with a microfone microphone and a receiver receiving a handset by subtraction of a compensation signal from the microphone signal and a specified in claim 8 method for suppressing feedback in a hearing by subtraction of a compensation signal from a microphone signal.

A common problem with hearing aids is the feedback between the output of the hearing aid and the input, which is annoying as feedback whistles. FIG. 1 shows the principle of an acoustic feedback using the example of a hearing aid 1. The hearing aid 1 comprises a microphone 2, which receives an acoustic useful signal 10, converts it into an electrical microphone signal 11 and outputs it to a signal processing unit 3. In the signal processing unit 3, the microphone signal 11 is, among other things, processed and amplified and output as a receiver signal 12 to a receiver 4. In the receiver 4, the electrical receiver signal 12 is again converted into an acoustic output signal 13 and delivered to the eardrum 7 of a hearing aid wearer.

The problem now is that a part of the acoustic output signal 13 passes through an acoustic feedback path 14 to the input of the hearing device 1, where it is superimposed on the useful signal 10 and recorded as a sum signal from the microphone 2. With a suitable phase position and amplitude of the fed-back output signal, disturbing feedback whistling occurs. In particular, by an open hearing aid supply, the attenuation of the acoustic feedback is low, whereby the problem is exacerbated.

To solve the problem adaptive systems for feedback suppression have been available for some time. In this case, the acoustic feedback path 14 is digitally reproduced. The replication takes place, for example, by means of an adaptive compensation filter 5, which is fed by the signal 12 driving the listener. After filtering in the compensation filter 5, a filtered compensation signal 15 is subtracted from the microphone signal 11. Ideally, the effect of the acoustic feedback path 14 is thereby canceled and there is a feedback-compensated input signal 16 of the signal processing unit 3.

For effective feedback suppression, adjustment of the filter coefficients of the adaptive compensation filter 5 is required. For this purpose, the input signal 16 of the signal processing unit 3 is evaluated by means of an analysis unit 6 and examined for possible feedback. The adaptation can cause artifacts, since 5 not optimal adaptive compensation filters 5 additional signal components are generated. In addition, in a not optimally adapted compensation filter 5, a feedback whistling may occur. In the EP 1 033 063 B1 such a hearing aid is disclosed, wherein two parallel adaptive compensation filters are used to improve the feedback suppression.

It is an object of the invention to provide a hearing apparatus and a method for improved feedback suppression.

According to the invention, the stated object is achieved with the hearing device of independent claim 1 and the method of independent claim 8.

The idea of the invention is to select from a plurality of preset static compensation filters the one appropriate for effective feedback cancellation.

The invention claims a hearing device for suppressing feedback with a microphone emitting a microphone signal and a receiver receiving a receiver signal by subtracting a compensation signal from the microphone signal. The hearing apparatus comprises a plurality of preset static first compensation filters for forming first compensation signals from the receiver signal and a first selection unit which selects a first compensation signal such that a feedback signal caused by the feedback is minimal in the receiver signal. The advantage of this is that no adaptation artifacts can occur.

In a further development, the hearing device may additionally comprise an adaptive first compensation filter for forming a further first compensation signal from the receiver signal. As a result, adaptation artifacts occur only when none of the static first compensation filters produces a better resulting signal than the adaptive first compensation filter.

In a further embodiment, the hearing device may comprise a preset static second compensation filter for forming a second compensation signal from the receiver signal and a second selection unit connected between the microphone and the first selection unit. The second selection unit subtracts the second compensation signal from the microphone signal, as a result of which a feedback signal caused by the feedback can be minimized in the receiver signal.

Furthermore, the second compensation filter can model a mechanical feedback path within the hearing device. This offers the advantage that due to the mechanical structure of the hearing device conditional feedback paths can be compensated.

In a further embodiment, the static first compensation filters may have different acoustic feedback paths model. As a result, "typical" feedback paths can be selectively suppressed.

In a development of the invention, the filter coefficients of the static first compensation filters can be determined by feedback path measurements. An advantage of this is the individual adaptation of the filter coefficients to the usage situation of the hearing device.

In addition, the hearing device may be a hearing aid.

The invention also claims a method for suppressing feedback in a hearing apparatus by subtracting a compensation signal from a microphone signal. The method includes forming first compensation signals from a listener signal by preset static first compensation filters and selecting one of the formed first compensation signals such that a feedback signal caused by the feedback is minimal in the listener signal.

In one development, the method comprises the formation of a further first compensation signal from the receiver signal by means of an adaptive first compensation filter.

In a further embodiment, the method comprises forming a second compensation signal from the receiver signal by a preset static second compensation filter and subtracting the second compensation signal from the microphone signal, thereby minimizing a feedback signal caused by the feedback in the input signal.

Furthermore, the second compensation filter can model a mechanical feedback path within the hearing device.

In another embodiment, the static first compensation filters may model different acoustic feedback paths.

In addition, the filter coefficients of the static first compensation filters can be determined by feedback path measurements.

Other features and advantages of the invention will become apparent from the following explanations of several embodiments with reference to schematic drawings.

Figur 1:

ein Schaltbild eines Hörgeräts mit Rückkopplungs- unterdrückung gemäß Stand der Technik,

Figur 2:

ein Prinzipschaltbild eines Hörgeräts mit mehreren statischen Kompensationsfiltern,

Figur 3:

ein Schaltbild eines weiteren Hörgeräts mit mehre- ren statischen Kompensationsfiltern,

Figur 4:

ein Prinzipschaltbild eines Hörgeräts mit mehreren statischen Kompensationsfiltern und einem adapti- ven Kompensationsfilter,

Figur 5:

ein Schaltbild eines weiteren Hörgeräts mit mehre- ren statischen Kompensationsfiltern und einem adaptiven Kompensationsfilter,

Figur 6:

ein Prinzipschaltbild eines Hörgeräts mit mehreren statischen Kompensationsfiltern, einem adaptiven Kompensationsfilter und einem zusätzlichen breit- bandigen statischen Kompensationsfilter und

Figur 7:

ein Schaltbild eines weiteren Hörgeräts mit mehre- ren statischen Kompensationsfiltern, einem adapti- ven Kompensationsfilter und einem zusätzlichen breitbandigen statischen Kompensationsfilter.

Show it:

FIG. 1:

1 is a circuit diagram of a hearing aid with feedback suppression according to the prior art;

FIG. 2:

a block diagram of a hearing aid with several static compensation filters,

FIG. 3:

a circuit diagram of another hearing aid with several static compensation filters,

FIG. 4:

a block diagram of a hearing aid with several static compensation filters and an adaptive compensation filter,

FIG. 5:

a circuit diagram of a further hearing aid with several static compensation filters and an adaptive compensation filter,

FIG. 6:

a schematic diagram of a hearing aid with multiple static compensation filters, an adaptive compensation filter and an additional broadband static compensation filter and

FIG. 7:

a circuit diagram of another hearing aid with several static compensation filters, an adaptive compensation filter and an additional broadband static compensation filter.

In the following embodiments, the invention will be explained using the example of a hearing aid. The explanatory remarks of course apply to other hearing aids.

FIG. 2 shows the principle of the invention by means of a circuit diagram. A microphone 2 of a hearing device 1 emits a microphone signal 11 which is picked up by a first selection unit 8. The microphone signal 11 is acted on by a feedback signal which is formed as a result of acoustic feedbacks between a receiver 4 of the hearing device 1 and the microphone 2. To suppress this feedback signal, a first compensation signal 151 is subtracted in the selection unit 8. The first compensation signal 151 should ideally completely compensate the feedback signal.

According to the invention, a plurality of first compensation signals 151 are therefore generated with the aid of static first compensation filters 51 from a receiver signal 12 which is present at the output of a signal processing unit 3 of the hearing device 1. The listener signal 12 is also the input signal of the listener 4. From an analysis of the microphone signal 11 and the compensation signals 151, the first selection unit 8 selects the most suitable compensation signal 151 and outputs the thus feedback-compensated microphone signal as an input signal 16 to the signal processing unit 3.

The filter coefficients of the static first compensation filters 51 are set to "typical" feedback paths. For example, the filter coefficients are metrologically determined by feedback path measurements on the ear of a hearing aid wearer at a hearing care professional. The use of static first compensation filters is possible because in the everyday environment of a hearing aid wearer sets a finite number of approximately uniform wear conditions and thus feedback paths. A large part of the feedback-critical situations can thus be "combated".

By using statically operating first compensation filters 51, no adaptation artifacts occur. To avoid artifacts when switching between different first compensation signals 151, instead of a "hard" switching, a controlled cross-fading between the compensation signals 151 can take place.

An implementation of the principle according to FIG. 2 is in FIG. 3 shown. The FIG. 3 shows the diagram of a hearing aid 1 with a microphone 2 for receiving sound and a handset 4 for delivering sound to the eardrum of a hearing aid wearer. Between microphone 2 and receiver 4, the microphone signal 11 emitted by the microphone 2 is freed from feedback in a first selection unit 8 and subsequently amplified in a signal processing unit, inter alia, and emitted as a receiver signal 12. From the receiver signal 12, compensation signals 151 are obtained with the aid of a plurality of static first compensation filters 51, which signals are supplied to the first selection unit 8.

In the first selection unit 8, the compensation signals 151 are each subtracted from the microphone signal 11 and fed as input signals 18 to a first switching unit 82. The first switching unit 82 switches through one of the input signals 18 and outputs it as a further input signal 16 to the signal processing unit 3. The first switching unit 82 is controlled by means of a first switching signal 19 from a first analysis unit 81. For this purpose, the first analysis unit 81 analyzes the input signals 18 of the first switching unit 82 and the microphone signal 11. Based on the analysis, that input signal 18 which has the most effective feedback suppression is selected. The analysis unit 81 decides, for example, based on a minimum energy of the input signal 18 or the minimization of a watermark in the input signal 18, which is impressed on the receiver signal 12.

In order to be able to encounter feedback paths that are not statically storable in a hearing aid, it is possible to combine the static first compensation filters 51 with an additional adaptive first compensation filter.

FIG. 4 shows the principle of the combination of static and adaptive compensation filters on the basis of a circuit diagram. A microphone 2 of a hearing device 1 emits a microphone signal 11 which is picked up by a first selection unit 8. The microphone signal 11 is acted on by a feedback signal which is formed as a result of acoustic feedbacks between a receiver 4 of the hearing device 1 and the microphone 2. To suppress this feedback signal, a first compensation signal 151 is subtracted in the first selection unit 8. The first compensation signal 151 should ideally be equal to the feedback signal.

According to the invention, a plurality of first compensation signals 151 are therefore generated with the aid of static first compensation filters 51 from a receiver signal 12 which is present at the output of a signal processing unit 3 of the hearing device 1. The handset signal 12 is also the input signal of the handset 4. In addition, an adaptive first compensation filter 53 generates a further first compensation signal 151 from the handset signal 12.

From an analysis of the microphone signal 11 and the compensation signals 151, the first selection unit 8 selects the most suitable and outputs the thus feedback-compensated microphone signal as an input signal 16 to the signal processing unit 3.

Adaptation artifacts only occur when none of the static first compensation filters 51 produces a better resulting input signal 18 than the adaptive first compensation filter 53. In addition, an adaptation control of the adaptive first compensation filter 53 can be used in the case of better static first compensation filter 51 whose filter coefficients take over as the starting value of the adaptation.

An implementation of the principle according to FIG. 4 is in FIG. 5 shown. The FIG. 5 shows the diagram of a hearing aid 1 with a microphone 2 for receiving sound and a handset 4 for delivering sound to the eardrum of a hearing aid wearer. Between the microphone 2 and the handset 4, the microphone signal 11 delivered by the microphone 2 is freed from feedback in a first selection unit 8 and subsequently amplified in a signal processing unit 3 and delivered as a handset signal 12. Compensation signals 151, which are supplied to the first selection unit 8, are obtained from the receiver signal 12 with the aid of a plurality of static first compensation filters 51 and an adaptive first compensation filter 53.

In the first selection unit 8, the compensation signals 151 are each subtracted from the microphone signal 11 and fed as input signal 18 to a first switching unit 82. The first switching unit 82 switches through one of the input signals 18 and outputs it as an input signal 16 to the signal processing unit 3. The first switching unit 13 is controlled by means of a first switching signal 19 from a first analysis unit 81. For this purpose, the first analysis unit 81 analyzes the input signals 18 of the first switching unit 82 and the microphone signal 11. Based on the analysis, that input signal 18 which has the most effective feedback suppression is selected. The analysis unit 81 decides, for example, based on a minimum energy of the input signal 18 or the minimization of a watermark in the input signal 18, which is impressed on the receiver signal 12.

The adaptive first compensation filter 53 is controlled by means of an analysis unit 6. The analysis unit 6 evaluates the first compensation signal 151 of the adaptive first compensation filter 53 subtracted from the microphone signal 11 and adjusts the filter coefficients of the adaptive first compensation filter 53 accordingly.

In addition to the changing external acoustic feedback path, another mechanical feedback path exists within the hearing aid. This path is generally subject to little variation and depends primarily on the design of the hearing aid. This mechanical feedback can be suppressed by another static compensation filter separately from the first compensation filters. The advantage of this is that, in contrast to an adaptive filter, such a filter can be used in a broadband manner since it does not cause any artifacts due to potential misadaptation of the filter coefficients. Therefore, a higher maximum amplification of the hearing aid can be achieved by canceling the feedback component by housing sound.

In FIG. 6 the use of an additional static compensation filter is shown in principle. The FIG. 6 shows on the basis of a circuit diagram in addition to the at FIG. 4 Components described between the microphone 2 and the first selection unit 8, a second selection unit 9. A second compensation signal 152 is formed by a static second compensation filter 52 from the receiver signal 12. The filter coefficients of the second compensation filter are selected such that mechanical feedbacks in the hearing aid housing are suppressed. The selection unit 9 selects whether the microphone signal 11 or the difference signal between the microphone signal 11 and the second compensation signal 152 is applied as an input signal 17 to the first selection unit 8.

In FIG. 7 is the implementation of the principle FIG. 6 exemplified. The FIG. 7 shows the wiring diagram of a

Hearing aid 1 according to FIG. 5 extended by a static second compensation filter 52 and a second selection unit 9. The selection unit 9 comprises a second switching unit 92 and a second analysis unit 91. The compensation signal 152 of the second compensation filter 52 is subtracted from the microphone signal 11 and supplied to the second switching unit 92 as an input signal 20. The microphone signal 11 is applied to a further input of the switching unit 92 itself. By the second switching signal 21 of the second analysis unit 92, the second switching unit 92 is controlled. From a comparison of the microphone signal 11 with the input signal 20, which are both supplied to the second analysis unit 91, the second analysis unit 91 detects whether a mechanical feedback is present. Accordingly, the turn-on of the feedback-reduced signal 20 is caused and the second switching unit 92 outputs an output signal 17 to the first selection unit 8.

LIST OF REFERENCE NUMBERS

1

hearing Aid

2

microphone

3

Signal processing unit

4

receiver

5

adaptive compensation filter

51

static first compensation filter

52

static first compensation filter

53

adaptive first compensation filter

6

analysis unit

7

eardrum

8th

first selection unit

81

first analysis unit

82

first switching unit

9

second selection unit

91

second analysis unit

92

second switching unit

10

payload

11

microphone signal

12

earpiece signal

13

output

14

acoustic feedback path

15

compensation signal

151

first compensation signal

152

second compensation signal

16

Input signal of the signal processing unit 3

17

Output signal of the second selection unit 9

18

Input signal of the first switching unit 82

19

first switching signal

20

Input signal of the second switching unit 92

21

second switching signal

Claims (13)

1. Hearing apparatus (1) for suppressing feedback, having a microphone (2) emitting a microphone signal (11) and a receiver (4) picking up a receiver signal (12), by subtracting a compensation signal (151, 152) from the microphone signal (11, 17),
   characterised by:

   - a number of preset static first compensation filters (51) for forming first compensation signals (151) from the receiver signal (12) and

   - a first selection unit (8), which selects a first compensation signal (151) such that a feedback signal caused by the feedback is minimal in the receiver signal (12).
2. Hearing apparatus (1) according to claim 1,
   characterised by:

   - an adaptive first compensation filter (53) for forming a further first compensation signal (151) from the receiver signal (12).
3. Hearing apparatus (1) according to claim 1 or 2, characterised by:

   - a preset static second compensation filter (52) for forming a second compensation signal (152) from the receiver signal (12) and

   - a second selection unit (9) connected between the microphone (2) and the first selection unit (8), which subtracts the second compensation signal (152) from the microphone signal (11), if this allows a feedback signal caused by the feedback to be minimised in the receiver signal (12).
4. Hearing apparatus (1) according to claim 3,
   characterised in that
   the second compensation filter (52) models a mechanical feedback path within the hearing apparatus (1).
5. Hearing apparatus (1) according to one of the preceding claims,
   characterised in that the static first compensation filters (51) model different acoustic feedback paths.
6. Hearing apparatus (1) according to claim 5,
   characterised in that the filter coefficients of the static first compensation filters (51) can be determined by means of feedback path measurements.
7. Hearing apparatus (1) according to one of the preceding claims,
   characterised in that the hearing apparatus is a hearing device.
8. Method for suppressing feedback in a hearing apparatus (1) by subtracting a compensation signal (151, 152) from a microphone signal (11, 17),
   characterised by:

   - forming first compensation signals (151) from a receiver signal (12) by means of preset static first compensation filters (51) and

   - selecting one of the formed first compensation signals (151) such that a feedback signal caused by the feedback is minimal in the receiver signal (12).
9. Method according to claim 8,
   characterised by:

   - forming a further first compensation signal (151) from the receiver signal (12) by means of an adaptive first compensation filter (53).
10. Method according to claim 8 or 9,
    characterised by:

    - forming a second compensation signal (152) from the receiver signal (12) by means of a preset static second compensation filter (52) and

    - subtracting the second compensation signal (152) from the microphone signal (11), if this allows a feedback signal caused by the feedback to be minimised in the receiver signal (12).
11. Method according to claim 10,
    characterised in that the second compensation filter (52) models a mechanical feedback path within the hearing apparatus (1).
12. Method according to one of claims 8 to 11,
    characterised in that the static first compensation filters (51) model different acoustic feedback paths.
13. Method according to claim 12,
    characterised in that the filter coefficients of the static first compensation filters (51) are determined by means of feedback path measurements.

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