#### STATISTICAL PROPERTIES OF STFT RATIOS FOR TWO CHANNEL SYSTEMS AND APPLICATIONS TO BLIND SOURCE SEPARATION

Radu Balan and Justinian Rosca, Siemens Corporate Research

frvbalan,roscag@scr.siemens.com

The ratio of the short time Fourier transform (STFT)
coefficients of signals received at two sensors can factor out
the role of the power spectrum of emitting sources, under
an assumption called disjoint orthogonality. Thus, it can
reveal parameters specific to the mixing scenario and serve
as a basis for channel estimation techniques.
In this paper we analyze and extend a source separation
method based on the use of STFT ratios of two sensor in
puts, called DUET. We generalize the problem formulation
in DUET, and prove that considerably weaker assumptions
about the classes of input signals are sufficient to apply the
derived techniques. The analysis centers on the notion of
ratioestimator and a novel stochastic model that enabled
us to derive the maximum likelihood ratioestimator.
Derived techniques can be effectively applied to source
separation, source localization, signal enhancement, and
noise reduction when using a twin microphone system, both
in echoic environments and degenerate situations.