Exploring the effect of target correlation on binaural speech intelligibility for quasi-anechoic and reverberated conditions

The transmission of the signal from a speech source and of the noise from one or multiple maskers can be fully described by the binaural impulse responses, which include all of the physical factors that are known to be relevant for speech intelligibility. In particular, binaural speech intelligibility outperforms monaural performance when dissimilarities of interaural levels and time delays can be detected at the ears. While a rich literature has investigated the role of masker's impulse responses and in particular how its correlation, besides level and time discrepancies, can modulate speech intelligibility, a similar detailed investigation for the target source cannot be found in the previous works. This work reviews the knowledge achieved so far on the topic and sets listening tests in quasi-anechoic and reverberated scenarios to examine the mechanisms by which target correlation might influence binaural speech intelligibility. It is found that target correlation can be singled out as a factor directly or indirectly in the listening tests; the indication given by the experiments is coherent with the previous interpretations of unmasking phenomena and with the idea that target correlation is supportive to the extraction of binaural timing cues that contribute to binaural performance.