Modelling of acoustic transfer functions for echo cancellers

ARMA modelling (infinite impulse response filters having both poles and zeros), rather than MA modelling, of acoustic transfer functions is potentially capable of reducing the number of coefficients required to achieve a given level of echo cancellation. The amount of reduction obtainable, however, has received little attention in the literature. To arrive at quantitative figures for the complexity reduction possible, equation error and output error ARMA and MA modelling of acoustic impulse responses are compared experimentally. It is shown, for both fullband and subband implementations, that the potential for reducing the number of coefficients required is small