Insight into linear periodically time-varying coherence reduction methods for stereophonic acoustic echo cancellation

The non-uniqueness problem of multi-channel acoustic echo cancellation can be solved by reducing the coherence between the loudspeaker signals. To this end, several coherence reduction methods have been proposed that aim at providing the best possible trade-off between signal decorrelation and degradation of the subjective audio quality. Among these, the periodically time-varying ones introduce, as the name indicates, a periodicity to the signals' statistical properties. These properties are here analysed to provide further insight into the effective coherence reduction achieved by these particular methods, and, thereafter, to predict the performance enhancement of a stereophonic acoustic echo canceller.