Frequency domain step-size control in non-stationary environments

The presented algorithm detects changes of the loud-speaker enclosure microphone (LEM) system in an acoustic echo cancellation setup under non-stationary noise conditions. Changes of the LEM system entail a mismatch of the cancellation filter, consequently making the beforehand cancelled echos audible again. The new algorithm avoids the reduction of the adaptation speed after these changes. System changes are detected by monitoring the different behavior of two coherences: these changes have only a small impact on the coherence between the microphone and the loudspeaker signal, whereas they significantly influence the coherence between the microphone signal and the output of the cancellation filter.