The Influence of Probe-Tone Parameters on the Shape of Psychophysical Tuning Curves in Normal-Hearing Listeners

Psychophysical tuning curves have become increasingly important in furthering the interpretation of traditional masking data. Although a substantial amount of relatively new information is available on psychophysical tuning curves, the analysis and interpretation of this information are diffcult because of the lack of consistency among the probe-tone parameters used. This study investigated the shape of psychophysical tuning curves under simultaneous masking as a function of three frequencies— 500, 1000, and 4000 Hz; three levels—5, 20, and 40 dB SL; and two durations—10 msec and 200 msec. of the probe tones.

The results indicate that the general shape of psychophysical tuning curves is consistent throughout the 18 combinations of parameter values studied. Irregularities such as notches and CF shifts, inconsistently noted in previous investigations, were observed in the shape of psychophysical tuning curves. However, they were shown to depend on unique combinations of probe-tone parameters. These results are compared to previous investigations of simultaneous-masking psychophysical tuning curves with respect to the specific effects of probe-tone parameter values on the shape of the curves. Irregularities in the shape of psychophysical tuning curves are discussed in relation to aural combination tones and other nonlinearities.