Patent ID: 7596220

Claim:
A method comprising: generating a first infinite impulse response (IIR) error signal by differencing a conditioned return signal and an input signal filtered by a first adaptive IIR filter wherein the first adaptive IIR filter comprises at least one feed-forward gain and at least one feedback gain adapted to be adjusted via a first IIR adaptation mechanism and wherein the first IIR adaptation mechanism is adapted to receive the generated first IIR error signal; selecting a signal from a group of signals comprising the input signal filtered by the first adaptive IIR filter and the conditioned return signal; and generating a finite-impulse response (FIR) error signal by differencing the selected signal and an input signal filtered by an adaptive FIR filter, wherein the adaptive FIR filter comprises at least one feed-forward gain adapted to be adjusted via a FIR adaptation mechanism and wherein the FIR adaptation mechanism is adapted to receive the generated FIR error signal; using the IIR error signal to assess and detect a stability state of the first adaptive IIR filter and when an instability of the first adaptive IIR filter is detected, selecting an output of the adaptive FIR filter as an echo signal estimate and resetting the first adaptive IIR filter.