Forward masking tuning curves with randomized masker frequencies

Abstract

Forward-masking psychophysical tuning curves broaden as the signal level is increased, and the detection of components remote from the nominal signal frequency is one of the mechanisms proposed to account for the observation [D. M. Green, B. R. Shelton, M. C. Picardi, and E. R. Hafter, J. Acoust. Soc. Am. 69, 1758–1762 (1981)]. It is reasonable to assume that the effectiveness of such a strategy would be maximized in the situation where the same signal and masker frequency is uncertain from one trial to the next. Tuning curves were obtained in 250-trial runs with maskers of 500, 750, 1000, 1250, and 1500 Hz either randomized from trial-to-trial or presented in five 50-trial blocks. The signal was a 1000-Hz tone of either 5 or 30 dB SL. The tuning curve broadened with the high signal level, but the randomization of masker frequency had little or no effect on the sharpness of tuning. Similar results have been reported for a simultaneous masking procedure [B. R. Glasberg, B. C. J. Moore, and R. A. Lufti, J. Acoust. Soc. Am. 72, 273–275 (1982)]. The data offer no support to the hypothesis that off-frequency listening can account for the broadening of psychophysical tuning curves with increased signal level. [Work supported by NSERC].