Abstract
These experiments are concerned with the frequency effects of two-tone suppression in forward and backward masking. In each experiment, the masked threshold of 15ms probe tone caused by the addition of a 600ms second masker (M2) to a 600 ms first masker (M1) was determined as a function of central frequency of a M2.
At appropriate F1 and F2, suppression showed significant magnitude both for forward and backward masking. Suppression was more prominent for F2 < F1 than for F2 > F1 in forward masking. This effect can be explained with help of the Hall's nonlinear model on the basiler membrane. Data in backward masking indicated that there is much more suppression for F2 < F1 than for F2 > F1 at higher frequencies of F1. For F2 > F1 than for F2 < F1 at lower frequencies of F1, however, suppression was more prominent.
The differences in the suppression effect observed in forward and backward masking support the idea that suppression in forward masking is generated within hair cells, but suppression in backward masking is dominated by central processes.
