Masking of Pure Tones by Broad-Band Noise in Cochlear-Impaired Listeners

Abstract

We measured masked thresholds for pulsed pure tones (.5, 1.0, 2.0, and 4.0 kHz) in the presence of different levels of broad-band noise (nominally 0, 20, 40, and 60 dB/Hz). Several of the 16 cochlear-impaired listeners displayed masked thresholds that were considerably higher than those obtained from 10 normal listeners. At the 60 dB/Hz noise level the correlation coefficients between thresholds in noise and thresholds in quiet were r = .36, .44, .63, and .64 for signal frequencies of .5, 1.0, 2.0, and 4.0 kHz, respectively. The growth of masking, as masker level was increased, was linear for the normal listeners but was disproportionate and nonlinear in some cochlear-impaired listeners. In these data and data from other studies, it is clear that thresholds in noise cannot be predicted from thresholds in quiet. Masked thresholds are related to other measures of frequency resolution and to speech intelligibility in noise, but it is argued that psychoacoustic tuning curves provide more direct measures of the auditory-filter characteristics.