Noise and late-reverberation suppression in time-varying acoustical environments

We consider single-channel blind late-reverberation suppression in noisy and time-varying acoustical environments. Existing estimators for the late reverberant spectral variance (LRSV) are derived assuming the room impulse responses (RIRs) to be time-invariant realizations of a stochastic process. In this paper, we go one step further and analyze time-varying RIRs. We show theoretically that existing LRSV estimators may still be used even when the individual RIR filter taps vary rapidly with time, provided that the reverberation time T₆₀ and direct-to-reverberation ratio (DRR) remain nearly constant during an interval of the order of a few frames. We show that these parameters can be taken frequency-independent in DFT-based enhancement algorithms. We estimate them blindly. Experiments with time-varying RIRs validate the analysis and show the importance of accurate estimation of the reverberant spectral variance. Experiments with additive non-stationary noise show the influence of T₆₀ and DRR estimation.