Dependence of loudness adaptation on frequency and level

The relation between simple loudness adaptation and exposure time was determined for continuous pure tones at eight frequencies from 0.125 to 16 kHz and five sensation levels (SL) from 5 to 40 dB. Adaptation was measured over a 6-min exposure period in eight young listeners with normal hearing by the method of successive magnitude estimation. Listeners judged loudness every 20 s by assigning a number that matched the loudness of the tone. At all frequencies, loudness declined over time, more so at low sensation levels than at higher ones, and more so at frequencies above 8 kHz than at lower frequencies, especially at 5- and 10-dB SL and at 16 kHz. Most of the adaptation occurred within the first 3 min of exposure, slowly approaching asymptote around 6 min. Additional measurements at 60 dB SL at three frequencies showed that loudness declined after 6 min by 16% at 2 kHz and by as much as 26% at 12 kHz. Results obtained by loudness matching closely agreed with those from magnitude estimation. Quantitative analyses revealed a clear relation between published excitation patterns based on masking patterns [E. Zwicker and H. Fasti, Psychoacoustics (1990)] and the current adaptation data. [Work supported by NIH.]