Temporary threshold shift measured with two psychophysical procedures.

Abstract

Studies of temporary threshold shift (TTS) typically use classical psychophysical procedures, such as the method of adjustment, which are known to confound the obtained measure of sensitivity with the subject's criterion for response. A distinguishing feature of TTS research is high variability in the postexposure estimates of sensitivity, both within and across subjects and within and across sessions. It is possible that fluctuations in the subject's criterion for response (rather than actual variations in sensitivity) are responsible both for misestimations of the magnitude of the hearing loss induced by exposure to particular intense sounds (the TTS), and for the high variability that is commonly observed. To test this possibility, postexposure recovery of sensitivity was followed using two psychophysical procedures, one acknowledged to be criterion-dependent and the other relatively criterion-free. Within each postexposure session, alternate estimates of sensitivity were obtained with a version of the method of adjustment and with adaptive, two-interval forced-choice. The postexposure estimates of hearing sensitivity obtained with the two procedures were found to differ statistically; however, the preexposure baseline measures differed by essentially identical amounts. Thus, the values of TTS were equivalent with the two psychophysical procedures. Further, the session-to-session variability was found not to be significantly different with the two methods. Thus, for our trained observers at least, differences in pre- and postexposure response criteria did not appear to be a contaminating factor in estimates of TTS, and there was little basis for choice between the two procedures in regard to session-to-session variability.