Method of using a dominant angle of incidence to reduce acoustic noise in a speech signal

Abstract

Fourier transform processing is applied to digital signals obtained by analog-to-digital conversion of signals supplied by two microphones spaced by a fixed distance to produce two series of discrete data each datum of which represents the energy and phase of a spectral frequency band of the received sound. A dominant angle of incidence representing the angle of incidence of a speech signal component of the received sound signal relative to the two microphones is determined from phase differences between the discrete data in the same frequency bands of the two series and is used to combined the two series of discrete data into a single instantaneous spectrum in which any speech signal component is amplified relative to the noise. A noise spectrum is updated by comparing for each frequency band of the instantaneous spectrum the absolute value of the difference between the dominant angle of incidence and the angle of incidence of the frequency band in question with a tolerance threshold, and setting the energy of the noise spectrum equal to that of the instantaneous spectrum if that difference is above the tolerance threshold. The updated noise spectrum is then subtracted from the instantaneous spectrum to obtain an output spectrum consisting of the speech spectrum.