Frequency DL duration functions and estimated excitation‐pattern slopes in normal and hearing‐impaired listeners

Abstract

When the frequency DL is plotted as a function of tonal duration, an abrupt change in the slope of the DL duration function is often observed [Liang and Chistovich, Soy. Phys. Acoust. 6, 75–80 (1961)]. Their explanation was that the DL is normally limited by the auditory filter bandwidth, but when the signal is shortened so that its bandwidth is broader than that of the auditory filter, the broader spectral bandwidth of the signal determines the size of the frequency DL. We tested a similar hypothesis using excitation‐pattern slopes and spectral slopes rather than bandwidths, and extended the hypothesis to predict DLs from hearing‐impaired listeners. DL duration functions and estimated excitation‐pattern slopes were obtained from five normal‐hearing and six hearing‐impaired listeners. The break points in DL duration functions predicted by equating excitation‐pattern and signal spectral slopes were in close agreement with the observed break points. As predicted by their more gradual excitation‐pattern slopes, the break points occured at shorter durations, or not at all, in the hearing‐impaired subjects. [Work supported by NINCDS Grants NS15451 and NS12125.]