Frequency selectivity in pure-tone forward masking

Abstract

In two pure-tone forward-masking experiments, modeled after classical simultaneous masking experiments, we have attempted to verify some of the commonly accepted features of auditory frequency selectivity. In both experiments the signal was a 20-msec pure tone, presented 10 msec after termination of a 200-msec pure-tone masker. An adaptive 2IFC paradigm was used to measure the threshold of detectability of the signal. In the first experiment the masker's intensity and frequency were fixed, and signal threshold was measured at several signal frequencies. The masking patterns thus obtained were similar to classical ones if masker intensity is low. With moderate- to high-level maskers (70–90 dB SPL), nonmonotonic patterns were obtained. For example, with an 80-dB masker at 1 kHz, signal threshold was the same as 1 kHz and 1.5 kHz, but 15 dB lower at 1.3 kHz and 1.8 kHz. This anomolous effect was both frequency and subject dependent. In the second experiment, the signal's level and frequency were fixed, and the masker was varied. The tuning curves thus obtained were quite similar to those from earlier psychophysical and physiological experiments.