Adaptive acoustic echo cancellation microphone

Abstract

In teleconferencing, speaker-phone systems have an annoying acoustic echo problem. The acoustic echo canceller using an adaptive transversal filter is an effective solution. However, very-high-order adaptive filters have computational and convergence problems. Furthermore, acoustic echoes picked up by multiple microphones make the real-time application very difficult to implement. In this paper, a new approach to these problems is proposed. This new acoustic echo cancellation microphone system consists of two closely positioned directional microphones pointed in opposite directions and an adaptive filter. The adaptive filter converges to the transfer function difference between the two echo paths, which are similar since the two microphones are close to each other and far away from the loudspeaker. Therefore, a very-low-order adaptive filter is sufficient to reduce the echo. The steady-state analysis of this new system shows significant improvement over the traditional system. The system is tested using real speech data collected from a typical conference room. The experimental and simulation results show that more than 26 dB of cancellation can be achieved during the receive mode with the filter order equal to 64.