Different auditory filter bandwidth estimates based on profile analysis, notched noise, and hybrid tasks

Auditory filter bandwidths were estimated in three experiments. The first e xperiment was a profile-analysis experiment. The stimuli were composed of s inusoidal components ranging in frequency from 200 to 5000 Hz. The standard stimulus was the sum of equal-amplitude tones, and the, signal stimulus ha d a power spectrum that varied up-down...up-down. The number of components ranged from four to 60. Interval-by-interval level randomization prevented the change in level of a single component from reliably indicating the chan ge from standard to signal. The second experiment was a notched-noise exper iment in which the 1000-Hz tone to be detected was added to a noise with a notch arithmetically centered at 1000 Hz. Detection thresholds were estimat ed both in the presence of and in the absence of level randomization. In th e third, hybrid, experiment a 1000-Hz tone was to be detected, and the mask er was composed of equal-amplitude sinusoidal components ranging in frequen cy from 200 to 5000 Hz. For this experiment, thresholds were estimated both in the presence and absence of level variation. For both the notched-noise and hybrid experiments, only modest effects of level randomization were ob tained. A variant of Durlach et al.'s channel model [''Towards a model for discrimination of broadband signals,'' J. Acoust. Sec. Am. 80, 63-72 (1986) ] was used to estimate auditory filter bandwidths for all three experiments . When a two-parameter roex(p,r) filter weighting function was used to fit the data, bandwidth estimates were approximately two to three times as larg e:for the two detection tasks than for the profile-analysis task. (C) 1999 Acoustical Society of America. (S0001-4966(99)01311-9].