Auditory discrimination abilities of professional musicians were compared with those of nonmusicians. The stimuli for the frequency-discrimination tasks were 300-msec sinusoidal tones, 300-msec square waves, and tone patterns consisting of ten 40-msec tones played sequentially. The musicians’ difference thresholds for single tones were between Δf /f=0.001 and 0.0045. One-half of the nonmusicians attained thresholds almost as low; the rest attained larger thresholds, up to Δf /f=0.017. The results for the pattern stimuli show a clearer separation between the nonmusicians and musicians, whose median difference thresholds were about three times smaller. However, nonmusician listeners who had previously trained with patterns not in the test set had different thresholds, substantially smaller than those obtained by the musicians. The appropriateness of preferential recruitment of musicians for psychoacoustic research is discussed. The responses to a musical background survey and correlations between the survey items and discrimination performance are contained in a supplement to this paper [PAPS JASMA 76, xxx-xx].

Internal noise was measured in two paradigms simultaneously. In one method the listener's agreement in choosing the same masker as the one in a pair that sounds most signal-like is used to estimate internal noise [D. M. Green, Psych. Rev. 71, 392--407 (1964)]. In the other the increment in detection performance on those trials having identical as opposed to different maskers is used t estimate internal noise [R. A. Siegel, unpublished Master's thesis, M.I.T. (1979)]. Most results place the estimate of additive internal nose as nearly equal to external noise variability. The estimates from the agreement method can be adversely affected by uncertainty regarding the observation interval and interval biases, whereas the estimates obtained with the detection method are highly sensitive to measurement errors.

Intensity discrimination thresholds were assessed in a series of experiments. Signals were in-phase increments in the level of one component of a multitone masker. The main parameters of interest were the effects of signal uncertainty (which frequency is tested on a given trial) and masker uncertainty (which components were selected as the multitone masker on a given trial). Thresholds were measured as a function of signal frequency, number of components, and amount of overall changes in masker level. The results suggest a form of profile processing, in which the signal is detected by comparing levels in adjacent critical bands. Such a mechanism will account for the relatively small effects generally observed with signal uncertainty, for masker uncertainty showing larger effects on thresholds than signal uncertainty, and for the near constancy of signal threshold despite large (60 dB) fluctuations in overall level of the stimulus in the two intervals of the forced-choice trial.

The detectability of sinusoidal signals added to repeatable noise bursts was measured under conditions of signal-frequency uncertainty and masker-waveform uncertainty. Either source of uncertainty raised thresholds by 2-5 dB over those measured in a fixed-signal, fixed-masker condition, while the combination of both types of uncertainty raised thresholds by 8-12 dB. The magnitude of these elevations are similar to those found in a previous study, which employed maskers composed of random sets of equal-amplitude tones (Spiegel et al., J. Acoust. Soc. AM. 70, 1015-1019 (1981)]. When masker level varied by up to 40 dB between the two intervals of a forced-choice trial, and signal thresholds were elevated by only 2.5 dB. The results support a form of profile analysis in which listeners detect signals by noticing a relative change in the masker spectrum.

Estimates of the effectiveness of selective auditory attention were obtained by adjusting the level of a target tone, which was presented as one 40-msec component in a ten-tone sequential pattern. When the levels of target and nontarget tones were the same, frequency-discrimination thresholds (delta f/f) following prolonged training varied from 0.01-0.02 for minimal-uncertainty testing conditions to 0.1-0.2 under high trial-to-trial stimulus uncertainty. The functions relating frequency discrimination to target-tone level are widely separated for the two conditions; comparing them, we conclude that the effects of selective auditory attention can be equated to a 50-dB variation in signal level. Patterns that had been well-learned during the minimal-stimulus (remembered standard) procedure. The results of these latter experiments are consistent with a "top-down" processing interpretation in which well-learned patterns are first identified to locate the portions requiring further resolution.