Circuit and method for adaptive suppression of acoustic feedback

The circuit for the adaptive suppression of the acoustic feedback is part of a digital hearing aid consisting of microphone (1), AD converter (2), subtractor (3), hearing correction (4). DA converter (5) receiver (6), delay element (9), filter (10), updating unit (11). Cross-member decorrelator (12), cross-member filter (13) and control unit (14). The acoustic transmission path is modeled with the feedback characteristic (7) and an adder (8). The present invention is characterized by the particular arrangement of the decorrelation filters (12, 13). A cross-member decorrelator (12) is used to decorrelate the echo-canceled input signal (en), and a cross-gate filter (13) is provided for decorrelating the delayed output signal (xn) by means of coefficients derived from the first decorrelation filter (12) (kn) arranged. The cross-member coefficients (kn) of the two decorrelation filters (12, 13) are determined by means of adaptive decorrelation of the echo-compensated input signal (en). This allows maximum grain convergence speeds with minimal distortion, since the updating of the filter coefficients takes place in terms of time and frequency mainly where the large amplifications in the hearing correction (4) occur.