Bernafon Ag

Ascom Audiosys Ag

Arthur Schaub

Remo Leber

In a method and a device for the signal processing in a hearing aid, in which coefficients of a filter for the frequency-dependent amplitude adaptation of an input signal are adapted in accordance with this input signal, the following steps are carried out:

Signal processing in a hearing aid

A circuit for adaptive suppression of acoustic feedback forms part of a digital hearing aid, comprising a microphone ( ), subtracter ( ), hearing correcting means ( ), receiver ( ), delay element ( ), filter ( ), updating unit ( ), lattice decorrelators ( ) and control unit ( ). The transmission path is modeled with the feedback characteristic ( ) and an adder ( ). First decorrelator ( ) decorrelates the echo-compensated input signal (en) and second decorrelator ( ) decorrelates the delayed output signal (x ) by using coefficients (k ) from first decorrelator ( ). The coefficients (k ) of the two filters ( ) are calculated by adaptive decorrelation of the echo-compensated input signal (e ). This permit maximum convergence rates for minimum distortions. Updating of the filter coefficients mainly takes place where the greatest amplifications occur in the hearing correcting means ( ). The fed-back signal components are continuously removed from the input signal.

Circuit and method for the adaptive suppression of an acoustic feedback

The suppression of interfering noise in an input signal ( ) takes place in a main signal path ( ), which contains neither a transformation in the frequency range nor a splitting-up into partial band signals, but only a suppression filter ( ). The transmission function of the suppression filter ( ) is periodically newly determined on the basis of attenuation factors, which are determined in a signal analysis path ( ), which lies parallel to the main signal path ( ). The attenuation factors are utilized for the attenuation of signal components in frequency bands with a significant proportion of interfering noise. The suppression filter ( ) is implemented as transversal filter, the impulse response of which is periodically newly calculated as a weighted sum of the impulse responses of transversal band-pass filters. The signal analysis path ( ) comprises transversal half-band filters ( ) with successively reduced processing rate arranged in a tree structure, which enable a splitting up into partial signals in eight or more frequency bands with a high clearness of modulation. In this manner, processing with a low signal delay and an investigation of the proportion of interfering noise in a sufficient number of frequency bands becomes possible at all with a sufficiently high clearness of modulation

Hearing aid

An analog-digital processing unit including an amplifier with amplification that is adjustable in stages, and a quantizer outlet connected downstream of the amplifier. The output of the quantizer acts as actual value to control the amplification of the amplifier. With the assistance of the instantaneous value output from the quantizer, and the instantaneous prevailing amplification, the signal values, compensated by the instantaneous amplification, are defined and are output in a memory and scaling unit.

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Wolfhausen, Switzerland

Arthur Schaub