Dual-microphone echo canceller for suppressing loud nonlinear echo

This paper proposes a new dual microphone echo canceller (DMEC) for suppressing loud nonlinear echo common with hands-free talk on small terminals such as cellphones. The proposed DMEC has an adaptive null former whose nulls by the dual microphones focus on cancelling the nonlinear echo which can not be cancelled by ordinary linear echo canceller. To focus on the nonlinear echo, an adaptive filter eliminates the linear echo components which may perturb the adaptive null former from the second microphone signal before the adaptive null former. The following linear echo canceller and echo suppressor eliminate the linear echo and the residual nonlinear echo in the first microphone signal. Nearend speech degradation by the echo suppressor is reduced because the nonlinear echo is already reduced by the adaptive null former. Evaluations with real cellphones demonstrate that the proposed DMEC can cancel out the loud nonlinear echo almost completely and obtain stable nearend speech quality.