Adaptive Gain Control for Enhanced Speech Intelligibility Under Reverberation

Abstract

Overlap-masking reduces speech intelligibility in reverberant environments. In contrast to additive noise, the masking signal depends on the past of the speech signal. An increase in output signal power is followed by an increase in reverberation power. Taking into consideration, the mechanics of reverberation is essential for the development of speech modifications that effectively increase intelligibility. This letter proposes a mathematical framework that optimizes the full-band signal power as a function of late reverberation power and the degree of signal nonstationarity. The prescribed signal gain is smoothed adaptively to suppress artifacts that may be introduced by rapid gain fluctuations due to frame-based processing. Compared to a reference method, it is shown that higher signal-to-late-reverberation ratio in nonstationary regions of the speech signal is achieved with less aggressive, on average, gain modification. A listening test with native English speakers on meaningful sentences under strong reverberation measured a consistent and significant improvement in intelligibility over natural speech and a reference method.