Abstract:
Psychophysical forward masking generally grows nonlinearly, with a given increase in signal level requiring a larger increase in masker level for the signal to remain at threshold. In the present experiments, a 10-ms sinusoidal signal was presented 2 ms after a 20-ms sinusoidal masker at the same frequency. Frequencies of 2 and 6 kHz were tested. It was shown that, while the masker level needed grew faster than the signal level at low signal levels, at medium signal levels the reverse was the case. These results can be understood in terms of a basilar membrane response that is compressive at medium levels and more linear at low and high levels. When the masker is in the compressive region and the signal is in the lower, more linear, region, then large increases in masker level are needed for a small increase in signal level. When the signal is in the compressive region and the masker is in the higher, more linear, region, then large increases in signal level are needed for a small increase in masker level. [Work supported by the Royal Society and the Wellcome Trust.]