Correlations between speech processing and auditory functions at 1 kHz

Abstract

Even when all relevant speech information is presented above threshold, intelligibility may still be reduced for hearing-impaired listeners. An attempt is made to relate impaired speech processing to a deterioration of specific auditory functions. Performance of hearing-impaired listeners is measured on psychoacoustic tests concerning temporal and spectral resolution, frequency and intensity discrimination, and temporal and spectral integration. All auditory functions are measured at 1 kHz. Speech reception is measured with the SRBT test (speech reception bandwidth threshold). This test determines the minimum width of a speech band with a center frequency of 1 kHz required for 50% intelligibility. A wider-than-normal SRBT can simply be the consequence of inaudibility of part of the speech signal. To account for this possibility, each SRBT is converted to an SII (speech intelligibility index, the new articulation index). This SII may be interpreted as the proportion of the total speech information required by the listener for 50% intelligibility. An elevated SII is considered an indication of impaired processing of suprathreshold speech. This may be caused by the deterioration of specific auditory functions. Relations between the performance on psychoacoustic tests and the (elevated) SII will be examined. [Work supported by the Foundation ‘‘Heinsius-Houbolt Fonds.’’]