Evaluation of CASA and BSS models for cocktail-party speech segregation

For speech segregation, a blind separation model (BSS) is tested together with a CASA model which is based on the localisation cue and the evaluation of the time delay of arrival (TDOA). The test database is composed of 332 binary mixture sentences recorded in stereo with a static set-up. These are truncated at 1 second for the simulations. For applying the two models, we cut the frequency domain in a variable number of subbands, which are processed independently. Then, we evaluate the gain, using reference signals recorded in isolation. Without using this reference, a coherence index is also established for the BSS model, which measures the degree of convergence. After a careful analysis, we find gains of about 1-3dB for the two methods, which are smaller than those published for the same task. The variation of the number of subbands allows an optimisation, and we obtain a significant peak at 4 subbands for the CASA model, and a smaller maximum at 2 subbands for the BSS model.