Speech enhancement using dual microphone adaptive noise canceller

Abstract

Subject of research. The subject of the study is the issue of rational placement of microphones of the main and reference channels of a two-channel adaptive noise canceller (ANC) for speech enhancement in presence of acoustic interference from a point source. An increase of the signal-to-noise ratio (SNR) at the output of the ANC relative to the input value of the main channel was chosen as a criterion for rational placement. The limitations of the model of direct propagation of signals in reverberation conditions are considered. Methods. The estimation of the SNR at the inputs of the main and reference channels is obtained on the basis of a geometric model of point sources of signal and interference and on the analytical expressions for transfer functions between signal and interference sources and microphones of the main and reference channels for a planar model of signal propagation in a free field. The main results. The conditions for microphones placement of dual channel ANC, increasing SNR, are determined. The conditions for reference channel microphone placement at a given position of main channel microphone are determined. Limitations of ANC efficiency under reverberation conditions are investigated. It is shown that the microphone of the reference channel should be located near the interference source. For large rooms, the use of dual-microphone arrays is proposed and possible signal processing algorithms (conditions of their application) are considered. To use a two-element microphone array, additional information about the position of the target source is required. Practical significance. The obtained results can be useful for distant speech acquisition in the presence of acoustic interference.