Objective limits for four varieties of putative loudness adaptation

Abstract

The four varieties included three monaural techniques: (1) tone decay (TD); (2) simple adaptation (SA); (3) ipsilateral comparison paradigm (ICP); and the binaural (4) simultaneous dichotic loudness balances (SDLB). ‘‘Loudness adaptation’’ indicates that over time, under some conditions, there is a perceived decrease in loudness, when the initial baseline stimulus is progressively assessed. The authors have found the following limits: (1) the classic TD occurred within about 30 dB of threshold for all values tested (250 to 8000 Hz). (2) Except near threshold, SA for the loudness of a continuous unmodulated tone was observed at or above 40 dB when the stimulus reached 6000 Hz, or more. (3) ICP adaptation, which depends on at least 5-s intensity modulation, was found at all values tested from 40 to 80 dB, and from 250 to 8000 Hz. It correlates significantly with TD, with suppression of transient evoked otoacoustic emissions, and at 8000 Hz with SA adaptation. (4) Binaural SDLB adaptation has been repeatedly found at 20 to 100 dB, at all frequencies tested. Factor analysis indicated that binaural SDLB has at least four component factors, including binaural interaction. Unless factors are separated, SDLB adaptation does not correlate with monaural adaptation.