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 Yi(k,m) of a noisy audio signal yi at an ith input 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 λV, λX of said first noise signal component v (representing reverberation) and said target signal component x, respectively, said estimates of λV and λX being jointly optimal in maximum likelihood sense, based on the statistical assumptions that a) the time-frequency representations Yi(k,m), Xi(k,m), and Vi(k,m) (and Wi(k,m)) of respective signals yi(n), and signal components xi, and vi (and wi) are zero-mean, complex-valued Gaussian distributed, b) that each of them are statistically independent across time m and frequency k, and c) that Xi(k,m) and Vi(k,m) (and Wi(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.
Multi-microphone method for estimation of target and noise spectral variances for speech degraded by reverberation and optionally additive noise