Measuring the threshold for speech reception by adaptive variation of the signal bandwidth. II. Hearing-impaired listeners

In a previous study [Noordhoek et al., J. Acoust. Sec. Am. 105, 2895-2902 ( 1999)], an adaptive test was developed to determine the speech-reception ba ndwidth threshold (SRBT), i.e., the width of a speech band around 1 kHz req uired for a 50% intelligibility score. In this test, the band-filtered spee ch is presented in complementary bandstop-filtered noise. In the present st udy, the performance of 34 hearing-impaired listeners was measured on this SRBT test and on more common SRT (speech-reception threshold) tests, namely the SRT in quiet, the standard SRT in noise (standard speech spectrum), an d the spectrally adapted SRT in noise (fitted to the individual's dynamic r ange). The aim was to investigate to what extent the performance on these t ests could be explained simply from audibility, as estimated with the SII ( speech intelligibility index) model, or require the assumption of suprathre shold deficits. For most listeners, an elevated SRT in quiet or an elevated standard SRT in noise could be explained on the basis of audibility. For t he spectrally adapted SRT in noise, and especially for the SRBT, the data o f most listeners could not be explained from audibility, suggesting that th e effects of suprathreshold deficits may be present. Possibly, such a defic it is an increased downward spread of masking. (C) 2000 Acoustical Society of America. [S0001-4966(00)03203-3].