Spectro-temporal modulation (STM) detection thresholds are strong predictors of speech intelligibility, capturing so-called “supra-threshold” hearing deficits. This study investigates potential mechanisms underlying STM detection as a window into speech perception difficulties. Detection thresholds were measured for amplitude modulation (AM) at 4 and 12 Hz rate, and for STM at the same modulation rates with spectral densities of 1 and 2 cycles/octave, using a 2.5-octave-wide pink noise carrier. Participants included 10 young normal-hearing (NH) listeners and 10 older hearing-impaired (HI) listeners. NH listeners showed distinct patterns across spectral densities between the lower and faster AM rate. HI listeners exhibited similar AM thresholds to NH listeners but showed reduced sensitivity and greater inter-individual variability in the STM tasks. To explore underlying mechanisms, the measured thresholds were compared to simulations from the Computational Model of Auditory Signal Processing and Perception. Individual hearing profiles were incorporated by estimating outer hair cell loss via Adaptive Categorical Loudness Scaling. The model accurately reproduced NH performance and the average sensitivity reduction in the HI group, but it did not capture the full variability among HI listeners. Further simulations explored the roles of outer and inner hair cell loss, offering insights into the mechanisms critical for STM detection.
Paulick et al. (Wed,) studied this question.
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