Quiet-only performance measures miss masking effects that reduce speech redundancy.

Evidence

Accounting for audibility effects in speech mixtures is not straightforward. While it is common to measure performance in quiet for the target stimuli used, this does not incorporate the fact that portions of the target are completely masked, which greatly reduces redundancy in the speech signal. Thus a new measure of “masked target audibility” was introduced. … Simple energy-based analyses have been used to quantify the available target in monaural speech mixtures (e.g. the ideal binary mask described by Wang 2005 ; ideal time-frequency segregation as explored by Brungart et al. 2006 ; and the glimpsing model of Cooke 2006 ). The basic approach is to identify regions in the time-frequency plane where the target energy exceeds the masker energy. The number of these glimpses is reduced as the SNR decreases, or as more masker talkers are added to the mixture. To define the available glimpses in symmetric binaural mixtures, we simply applied a monaural glimpsing model separately to the two ears. For symmetric listening situations, the glimpses can occur in either ear, and often occur in both ears for a particular time-frequency tile. However the glimpses may not all be above threshold, particularly for listeners with hearing loss. Thus we conducted an experiment in which we presented “glimpsed” stimuli to NH and HI listeners to measure their ability to use the available target information. Performance was compared to natural binaural performance to determine to what extent target audibility/availability can explain performance. — Dijk, Pim van, Physiology, Psychoacoustics and…, 1754

Categorization

• DEFINE: Introduces ‘masked target audibility’ and the glimpsing model concept as a way to quantify available target information in speech mixtures.
• QUESTION: Worth chasing: do glimpses present in only one ear vs both ears confer any advantage, and how do hearing-loss thresholds interact with the binaural glimpsing count?