Multi-microphone method for estimation of target and noise spectral variances for speech degraded by reverberation and optionally additive noise

Abstract

The application relates to an audio processing system and a method of processing a noisy (e.g. reverberant) signal comprising first (v) and optionally second (w) noise signal components and a target signal component (x), the method comprising a) Providing or receiving a time-frequency representation Y(k,m) of a noisy audio signal yat an iinput unit, i=1, 2, . . . , M, where M≧2; b) Providing (e.g. predefined spatial) characteristics of said target signal component and said noise signal component(s); and c) Estimating spectral variances or scaled versions thereof λ, λof said first noise signal component v (representing reverberation) and said target signal component x, respectively, said estimates of λand λbeing jointly optimal in maximum likelihood sense, based on the statistical assumptions that a) the time-frequency representations Y(k,m), X(k,m), and V(k,m) (and W(k,m)) of respective signals y(n), and signal components x, and v(and w) are zero-mean, complex-valued Gaussian distributed, b) that each of them are statistically independent across time m and frequency k, and c) that X(k,m) and V(k,m) (and W(k,m)) are uncorrelated. An advantage of the invention is that it provides the basis for an improved intelligibility of an input speech signal. The invention may e.g. be used for hearing assistance devices, e.g. hearing aids.