Patent Application
20100329493
This application claims the priority, under 35 U.S.C. §119, of German Patent Application DE10 2009 031 135.1, filed Jun. 30, 2009; the prior application is herewith incorporated by reference in its entirety.
The invention relates to a hearing apparatus for suppressing feedback having a microphone emitting a microphone signal and a receiver picking up a receiver signal by subtracting a compensation signal from the microphone signal. The invention also relates to a method for suppressing feedback in a hearing apparatus by subtracting a compensation signal from a microphone signal.
A frequent problem with hearing apparatuses is feedback between an output of the hearing apparatus and an input, in which such feedback is experienced as interference in the form of whistling.
The problem is that some of the acoustic output signal 13 reaches the input of the hearing device 1 by way of an acoustic feedback path 14, is overlaid there with the useful signal 10 and is picked up by the microphone 2 as a sum signal. Corresponding phasing and amplitude of the fed back output signal produce interference in the form of feedback whistle. Attenuation of acoustic feedback is low due to open hearing device coverage in particular, thereby exacerbating the problem.
Adaptive systems for feedback suppression have been available for some time in order to resolve the problem. With those systems, the acoustic feedback path 14 is simulated digitally. Simulation takes place, for example, through the use of an adaptive compensation filter 5, which is supplied, for example, by the signal 12 driving the receiver. After filtering in the compensation filter 5, a filtered compensation signal 15 is subtracted from the microphone signal 11. This ideally cancels the effect of the acoustic feedback path 14 and an input signal 16 of the signal processing unit 3 with feedback compensation results.
It is necessary to regulate or adjust the filter coefficients of the adaptive compensation filter 5 for effective feedback suppression. To that end, an analysis unit 6 is used to evaluate the input signal 16 of the signal processing unit 3 and check for possible feedback. The adjustment may cause artifacts to be produced, since additional signal components are generated if the compensation filters 5 are not optimally adaptive. Feedback whistle can also occur if a compensation filter 5 is not adapted optimally. European Patent EP 1 033 063 B1 discloses such a hearing device, with which two adaptive compensation filters operating in parallel are used to improve feedback suppression.
It is accordingly an object of the invention to provide a hearing apparatus and a method for improved feedback suppression in a hearing apparatus, which overcome the hereinafore-mentioned disadvantages of the heretofore-known apparatuses and methods of this general type.
The concept of the invention is to select the compensation filter that is suitable for effective feedback suppression from a number of previously set static compensation filters.
With the foregoing and other objects in view there is provided, in accordance with the invention, a hearing apparatus for suppressing feedback. The hearing apparatus comprises a microphone emitting a microphone signal, a receiver picking up a receiver signal, a plurality of preset static first compensation filters for forming first compensation signals from the receiver signal, and a first selection unit selecting and subtracting a first compensation signal from the microphone signal in such a way that a feedback signal caused by the feedback is minimal in the receiver signal. This has the advantage that no adaptation artifacts can occur.
In accordance with another feature of the invention, the hearing apparatus can also include an adaptive first compensation filter for forming a further first compensation signal from the receivere signal. As a result, adaptation artifacts only occur if none of the static first compensation filters generates a better resulting signal than the adaptive first compensation filter.
In accordance with a further feature of the invention, the hearing apparatus can include 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, if this allows a feedback signal caused by the feedback to be minimized in the receiver signal.
In accordance with an added feature of the invention, the second compensation filter can also model a mechanical feedback path within the hearing apparatus. This has the advantage that it is possible to compensate for feedback paths due to the mechanical structure of the hearing apparatus.
In accordance with an additional feature of the invention, the static first compensation filters can model different acoustic feedback paths. This allows “typical” feedback paths to be suppressed specifically.
In accordance with yet another feature of the invention, the filter coefficients of the static first compensation filters can be determined by feedback path measurements. This has the advantage that the filter coefficients can be adjusted individually to the use situation of the hearing apparatus.
In accordance with yet a further feature of the invention, the hearing apparatus can also be a hearing device or hearing aid.
With the objects of the invention in view, there is also provided a method for suppressing feedback in a hearing apparatus. The method comprises forming first compensation signals from a receiver signal using preset static first compensation filters, and selecting and subtracting one of the formed first compensation signals from a microphone signal in such a way that a feedback signal caused by the feedback is minimal in the receiver signal.
In accordance with another mode of the invention, the method includes forming a further first compensation signal from the receiver signal through the use of an adaptive first compensation filter.
In accordance with a further mode of the invention, the method includes forming a second compensation signal from the receiver signal through the use of a preset static second compensation filter and subtracting the second compensation signal from the microphone signal, if this allows a feedback signal caused by the feedback to be minimized in the input signal.
In accordance with an added mode of the invention, the second compensation filter can also model a mechanical feedback path within the hearing apparatus.
In accordance with an additional mode of the invention, the static first compensation filters can model different acoustic feedback paths.
In accordance with a concomitant mode of the invention, the filter coefficients of the static first compensation filters can also be determined by feedback path measurements.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a hearing apparatus and a method for suppressing feedback in a hearing apparatus, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Referring now in detail to the figures of the drawings and first, particularly, to
Therefore, according to the invention, a number of first compensation signals 151 are generated from a receiver signal 12, which is present at the output of a signal processing unit 3 of the hearing device 1, with the aid of static first compensation filters 51. The receiver signal 12 is also the input signal of the receiver 4. The first selection unit 8 selects the most suitable compensation signal 151 from an analysis of the microphone signal 11 and the compensation signals 151 and emits the microphone signal, which thus has feedback compensation, 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. The filter coefficients are determined by a hearing device acoustician using measuring techniques through the use of feedback path measurements, for example at the ear of a hearing device wearer. The use of static first compensation filters is possible, because in the everyday environment of a hearing device user there are a finite number of approximately identical wearing conditions and therefore feedback paths. A large proportion of feedback-critical situations can therefore be overcome.
The use of statically operating first compensation filters 51 means that adaptation artifacts do not occur. In order to avoid artifacts when switching between different first compensation signals 151, it is possible for a controlled cross-fading to take place between the compensation signals 151 rather than a “hard” switching.
An application of the principle according to
In the first selection unit 8, the compensation signals 151 are respectively subtracted from the microphone signal 11 and supplied as input signals 18 to a first switching unit 82. The first switching unit 82 switches one of the input signals 18 through and emits it as a further input signal 16 to the signal processing unit 3. The first switching unit 82 is controlled by a first analysis unit 81 with the aid of a first switching signal 19. To this end, the first analysis unit 81 analyzes the input signals 18 of the first switching unit 82 and the microphone signal 11. The input signal 18 having the most effective feedback suppression is selected on the basis of the analysis. The analysis unit 81 decides, for example, on the basis of a minimum energy of the input signal 18 or a minimization of a water mark in the input signal 18, which is impressed onto the receiver signal 12.
In order to also be able to counteract feedback paths, which cannot be stored statically in a hearing device, it is possible to combine the static first compensation filters 51 with an additional adaptive first compensation filter.
Therefore, according to the invention, a number of first compensation signals 151 are generated from a receiver signal 12 with the aid of static first compensation filters 51. The receiver signal 12 is present at the output of a signal processing unit 3 of the hearing device 1. The receiver signal 12 is also the input signal of the receiver 4. An adaptive first compensation filter 53 also generates a further first compensation signal 151 from the receiver signal 12.
The first selection unit 8 selects the most suitable signal from an analysis of the microphone signal 11 and the compensation signals 151 and emits the microphone signal which thus has feedback compensation, as an input signal 16 to the signal processing unit 3.
Adaptation artifacts then only occur if none of the static first compensation filters 51 generates a better resulting input signal 18 than the adaptive first compensation filter 53. In the case of a better static first compensation filter 51, an adaptation control of the adaptive first compensation filter 53 can also adopt the former's filter coefficients as a start value for the adaptation.
An application of the principle according to
In the first selection unit 8, the compensation signals 151 are respectively subtracted from the microphone signal 11 and supplied as the input signal 18 to a first switching unit 82. The first switching unit 82 switches one of the input signals 18 through and emits it as the input signal 16 to the signal processing unit 3. The first switching unit 82 is controlled by a first analysis unit 81 with the aid of a first switching signal 19. To this end, the first analysis unit 81 analyzes the input signals 18 of the first switching unit 82 and the microphone signal 11. The input signal 18 having the most effective feedback suppression is selected on the basis of the analysis. The analysis unit 81 decides, for example, on the basis of a minimum energy of the input signal 18 or a minimization of a water mark in the input signal 18, which is impressed onto the receiver signal 12.
The adaptive first compensation filter 53 is controlled with the aid 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 sets the filter coefficients of the adaptive first compensation filter 53 correspondingly.
There is also a further, mechanical, feedback path within the hearing device, as well as the changing external acoustic feedback path. This further path is generally only subject to minor fluctuations and is primarily a function of the structure of the hearing device. This mechanical feedback can be suppressed by a further static compensation filter separately from the first compensation filters. This has the advantage that, unlike an adaptive filter, such a filter can be used wideband since it does not produce any artifacts due to potential incorrect adaptation of the filter coefficients. It is therefore possible to achieve greater maximum amplification of the hearing device by obliterating the feedback element due to housing sound.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2009 031 135.1 | Jun 2009 | DE | national |
