Patent Application
20120082330
This application claims the priority, under 35 U.S.C. §119, of German patent application DE 10 2010 041 740.8, filed Sep. 30, 2010; the prior application is herewith incorporated by reference in its entirety.
The invention relates to a method for signal processing in a hearing aid and to a hearing aid in which an input signal is subdivided into a plurality of frequency bands.
It is established practice in hearing aids to use dynamic compression in order to compensate for a user's hearing loss, in particular when a recruitment is present. The real acoustic environment is mapped into the residual dynamic range of the hearing-impaired user by means of the dynamic compression. In such cases the residual dynamic range is defined by the user's hearing threshold and threshold of discomfort. The residual dynamic range is frequency-dependent.
The mapping of the real acoustic environment onto the residual dynamic range of the hearing-impaired person is accomplished by means of automatic gain control (AGC). The use of output-level-controlled automatic gain control (AGCO) and input-level-controlled automatic gain control (AGCI) are well-known in this context.
As an example of output-level-controlled dynamic compression, reference is had to U.S. Pat. No. 6,731,767 B1 and its counterpart international publication No. WO 00/47014, which describe a so-called Adaptive Dynamic Range Optimization (ADRO) compression. With that approach the output level is used for controlling the amplification, and moreover not simply for level limiting but also for (slow) compression across the entire dynamic range, an attempt being made in the process to apply a linear gain and its advantages in respect of sound and speech intelligibility against background noise.
The use of output-level-controlled and input-level-controlled dynamic compression in a hearing aid is described in the commonly assigned patent application publication No. US 2007/0140512 A1 and its counterpart German published patent application DE 10 2005 061 000 A1. Switching between the different dynamic compression algorithms is effected on the basis of the assignment of the input signal entering the respective hearing aid to a specific hearing environment (classification).
Commonly assigned patent application publication No. US 2007/0053535 A1 and its counterpart German published patent application DE 10 2009 004 185 A1 describe the simultaneous use of both output-level-controlled dynamic compression and input-level-controlled dynamic compression in a hearing aid, wherein the different dynamic compression modes are performed in two parallel signal paths and the two signal paths are merged using weighting that is dependent on the classification.
Extensive studies carried out with the different types of dynamic compression have revealed that it makes sense to give precedence to one of the two compression modes in certain hearing situations. The choice made or weighting applied can be determined e.g. on the basis of a classification system which decides in which acoustic hearing environment the hearing aid is currently situated. Thus, output-level-controlled dynamic compression (AGCO), e.g. ADRO (Adaptive Dynamic Range Optimization) compression, is preferred, for instance in a very loud hearing environment. If, on the other hand, a hearing situation is detected in which a strong voice signal is present, then input-level-controlled dynamic compression (AGCI), e.g. WDRC (Wide Dynamic Range Compression) compression, is preferred. The studies mentioned have shown in particular that the type of compression has an effect on the perception of a specific input signal. Thus, in ADRO compression, for example, a significant impact on the perception of loudness is evident, while WDRC compression improves the perception of speech. It is therefore advantageous to perform the dynamic compression as a function of the classification.
It is accordingly an object of the invention to provide a hearing aid and a signal processing method which overcome the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides for a further improvement in the perception of acoustic signals in the provision of hearing assistance by way of a hearing aid.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for signal processing in a hearing aid, the method which comprises the following steps:
receiving an input signal and dividing the input signal into a plurality of frequency bands;
performing input-level-controlled dynamic compression in at least one first frequency band of the plurality of frequency bands;
performing output-level-controlled dynamic compression in at least one second frequency band of the plurality of frequency bands; and outputting an output signal.
The invention initially makes provision for an acoustic input signal to be subdivided into a plurality of frequency bands (channels). In principle this can also entail a very large number of frequency bands, as results for example in the digital transformation of the input signal from the time domain into the frequency domain, by way of a digital FFT (fast Fourier transform) for example. Usually, however, the acoustic input signal is subdivided into a manageable number of frequency bands (e.g. 16) by means of a filter bank. According to the invention input-level-controlled dynamic compression (AGCI) now takes place in at least one of the generated frequency bands and simultaneously output-level-controlled dynamic compression (AGCO) is performed in at least one other frequency band. For example, output-level-controlled compression (AGCO) can be used in at least one frequency band in the low frequency range of the acoustic input signal, since low frequencies have a significant effect on the perception of loudness, which means that a form of compression that positively influences the loudness perception is advantageous in the low frequency range. In the upper frequency range, on the other hand, input-level-controlled compression is advantageously used, since this frequency range is more dominant with regard to speech intelligibility and input-level-controlled compression (AGCI) has an advantageous effect on speech intelligibility. However, in the case of a hearing aid according to the invention it is advantageously possible to assign any type of compression to each channel.
In accordance with an added feature of the invention, the signal path in at least one frequency band is subdivided into at least two parallel signal paths. In this case input-level-controlled dynamic compression (AGCI) is performed in a first signal path within the respective frequency band and output-level-controlled dynamic compression (AGCO) is performed in a second signal path of the respective frequency band before the signal paths are merged once more. This has the advantage that it is possible to switch between the different compression types in the respective frequency band, and moreover independently of the compression type chosen in another frequency band. This enables the signal processing of the hearing aid to be adapted more effectively to different hearing situations.
In a further embodiment variant of the invention in which the signal processing is performed in at least two parallel signal paths in at least one frequency band, no switching takes place between the individual signal paths, but instead, following the respective execution of different types of dynamic compression, the signal paths are merged in a specific mixing ratio, i.e. using different weightings. This permits the signal processing in the respective hearing aid to be adapted even more effectively to different hearing situations. The system described would basically no longer require a classification, since the signal processing is constantly operated with input-level-controlled and output-level-controlled dynamic compression. The different compression methods could, however, also be activated and deactivated automatically in a frequency-dependent manner as a function of the classification or be linked to one another with a different weighting in the respective frequency band. This switching or mixing is advantageously performed not only on the basis of the classification, which tends to take physical variables into account, but also with the inclusion of psychoacoustic variables.
All in all the invention offers the advantage that a hearing aid according to the invention operates in a frequency-specific manner also in relation to the dynamic compression. Thus, the advantages of input- and output-related gain control can be exploited simultaneously in a specific acoustic situation.
In a preferred embodiment variant of the invention the input-level-controlled dynamic compression (AGCI) is performed as WDRC (Wide Dynamic Range Compression) compression. In an advantageous embodiment variant of the invention the output-level-controlled compression (AGCO) is furthermore performed as ADRO (Adaptive Dynamic Range Optimization) compression.
The assignment of the different compression methods to the individual frequency bands or to the individual signal paths within the individual frequency bands can advantageously be specified by programming of a respective hearing aid, by a hearing aid acoustician for example. Furthermore, in a hearing aid having a plurality of parallel signal paths within one frequency band, in which signal paths different types of dynamic compression are performed, the mixing ratio between the individual signal paths is advantageously also adjustable by means of programming. In this case the ratio is preferably also set as a function of the individual hearing loss of the user.
In a particularly advantageous embodiment variant of the invention the assignment of the different compression methods to the individual frequency bands as well as where appropriate also the mixing ratio of the parallel signal paths within a frequency band can change in the course of the ongoing operation of a respective hearing aid. The setting is advantageously carried out adaptively as a function of the current hearing situation in which the hearing aid is being operated and which is established with the aid of a classifier.
With the above and other objects in view there is also provided, in accordance with the invention, a hearing aid that is specifically configured for carrying out the above-summarized method. The apparatus comprises:
an input transducer for acquiring an acoustic input signal and converting the input signal into an electrical input signal;
a filter bank for dividing the electrical input signal into a plurality of frequency bands;
means for performing output-level-controlled dynamic compression in at least one first frequency band of the plurality of frequency bands;
means for performing input-level-controlled dynamic compression in at least one second frequency band of the plurality of frequency bands;
a merging device for merging output signals of the individual frequency bands into an overall electrical output signal; and
an output converter for converting the overall electrical output signal into an output signal to be perceived as an acoustic output signal by a user.
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 method for signal processing in a hearing aid and hearing aid, 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 to the figures of the drawing in detail and first, particularly, to
Analogously to
A further block diagram of a hearing aid according to the prior art is shown in
An exemplary block diagram of a hearing aid according to the invention is shown in
A particularly advantageous embodiment variant of the invention is shown in the block diagram according to
If only the numerical values 0 or 1 are allowed for the factors, it is possible to switch between the different types of dynamic compression in each frequency band. Obviously a gradual transition is also possible here, in that no hard switchover between 0 and 1 is performed.
The individual weights of the signal paths can advantageously be set by programming the respective hearing aid. Preferably the weights are adjusted dynamically during the ongoing operation of the hearing aid. For this purpose the electrical input signal emitted by the microphone 51 and the output signals of the filter bank FBA5 are supplied and analyzed in the classification and control unit K5. The weights are then set accordingly as a function of the detected hearing situation. Thus, in the hearing situation “speech in noise”, for example, the weights are set such that the resulting signal processing by the hearing aid is performed according to the exemplary embodiment illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 041 740.8 | Sep 2010 | DE | national |
