Audibility thresholds were measured at 500 and 4000 Hz with a standard clinical procedure and a two-interval, forced-choice (2IFC) adaptive procedure for 72 normal-hearing and hearing-impaired listeners, age 17 to 83. Psychometric functions were obtained for clinical, 2IFC, and Yes-No procedures. A measure of response bias was obtained from the Yes-No procedure. The 2IFC adaptive thresholds were 6.5 dB lower than audiological thresholds. The psychometric functions for the forced-choice procedures were generally shallower than those for the clinical procedure and were shifted to lower sound pressure levels. Response bias played a small role at best in accounting for the magnitude of the difference in threshold estimated by the adaptive and clinical procedures or for the differences among the psychometric functions.
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