Pitfalls in behavioral estimates of basilar-membrane compression in humans.
Psychoacoustic estimates of basilar-membrane compression often compare on- and off-frequency forward masking. Such estimates involve assuming that the recovery from forward masking for a given signal frequency is independent of masker frequency. To test this assumption, thresholds for a brief 4-kHz signal were measured as a function of masker-signal delay. Comparisons were made between on-frequency (4 kHz) and off-frequency (either 2.4 or 4.4 kHz) maskers, adjusted in level to produce the same amount of masking at a 0-ms delay between masker offset and signal onset. Consistent with the assumption, forward-masking recovery from a moderate-level (83 dB SPL) 2.4-kHz masker and a high-level (92 dB SPL) 4.4-kHz masker was the same as from the equivalent on-frequency maskers. In contrast, recovery from a high-level (92 dB SPL) 2.4-kHz forward masker was slower than from the equivalent on-frequency masker. The results were used to simulate temporal masking curves, taking into account the differences in on- and off-frequency masking recoveries at high levels. The predictions suggest that compression estimates assuming frequency-independent masking recovery may overestimate compression by as much as a factor of 2. The results suggest caution in interpreting forward-masking data in terms of basilar-membrane compression, particularly when high-level maskers are involved.
Wojtczak
Magdalena
M
Department of Psychology, University of Minnesota, Minneapolis, Minnesota 55455, USA. wojtc001@umn.edu
Oxenham
Andrew J
AJ
D001309:Auditory Threshold / Q000502:physiology; D001489:Basilar Membrane / Q000502:physiology*; D006801:Humans; D010470:Perceptual Masking / Q000502:physiology; D011312:Pressure; D011571:Psychoacoustics; D013997:Time Factors