Circuit and method for the adaptive suppression of an acoustic feedback

Circuit for the adaptive suppression of acoustic feedback in an acoustic system having at least one microphone (1) for producing an electric input signal (dt)), at least one loudspeaker or receiver (6) and an interposed electronic signal processing part, incorporating a filter (10) for modelling a feedback characteristic (7), an updating unit (11) for calculating current coefficients (wn) for the filter (10), a subtracter (3) for calculating an echo-compensated input signal (en) by subtracting an echo estimate (yn) delivered by the filter (10) from a digital input signal (dn), a delay element (9) for calculating a delayed output signal (xn), a first adaptive decorrelation filter (12) and a second adaptive decorrelation filter (13), characterized in that the two decorrelation filters (12, 13) are constructed as lattice decorrelation filters, that the first decorrelation filter (12) is provided for decorrelating the echo-compensated input signal (en) and the second decorrelation filter (13) for decorrelating the delayed output signal (xn) by means of coefficients (kn) from the first decorrelation filter (12), and that the two decorrelation filters (12, 13) are configured for calculating their lattice coefficients (kn) by adaptive decorrelation of the echo-compensated input signal (en).