Spectro-Temporal Modulation Transfer Functions and Speech Intelligibility

Abstract

Detection thresholds for spectral and temporal modulations are measuredusing broadband spectra with sinusoidally rippled profiles that drift up or down the log-frequency axis at constant velocities. Spectro-temporal Modulation Transfer Functions (MTF) are derived as a function of ripple peak density (cycles/octave) and drifting velocity (Hz). MTFs exhibit a lowpass function with respect to both dimensions, with 50 percent bandwidths ofabout 16 Hz and 2 cycles/octave. The data replicate (as special cases) previously measured purely temporal MTFs [Viemeister, 1979] and purely spectral MTFs [Green, 1986].<p>We present a computational auditory model that exhibits spectro-temporal MTFs consistent with the salient trends in the data.The model is used to demonstrate the potential relevance of these MTFsto the assessment of speech intelligibility in noise and reverberantconditions.