Dual-microphone speech dereverberation using a reference signal

Speech signals recorded with a distant microphone usually contain reverberation, which degrades the fidelity and intelligibility of speech, and the recognition performance of automatic speech recognition systems. In this paper we propose a speech dereverberation system which uses two microphones. A Generalized Sidelobe Canceller (GSC) type of structure is used to enhance the desired speech signal. The GSC structure is used to create two signals. The first signal is the output of a standard delay and sum beamformer, and the second signal is a reference signal which is constructed such that the direct speech signal is blocked. We propose to utilize the reverberation which is present in the reference signal to enhance the output of the delay and sum beamformer. The power envelope of the reference signal and the power envelope of the output of the delay and sum beamformer are used to estimate the residual reverberation in the output of the delay and sum beamformer. The output of the delay and sum beamformer is then enhanced using a spectral enhancement technique. The proposed method only requires an estimate of the direction of arrival of the desired speech source. Experiments using simulated room impulse responses are presented and show significant reverberation reduction while keeping the speech distortion low.