| Popis: |
Experienced listeners identified the longer of two unfilled time intervals, each bounded by acoustic markers. Time‐difference thresholds (d′ = 1.0) were measured under a variety of conditions in a four‐level, 2AFC procedure. When all four tonal markers were identical and at a high level (86 dB SPL), tonal frequency did not affect performance. For 1‐kHz markers, performance deteriorated as their intensity was creased below 25 dB SL. When the markers of each interval differed in intensity or in frequency, performance also decreased and the time‐difference threshold was not monotonically related to base duration. This nonmonotonicity was also observed when the time intervals were hounded by a 10‐msec burst of bandpass (800–2000 Hz) noise at 71 dB SPL and by a 500‐msec buzz formed from 100 pulses/sec, filtered with “formants” at 630 and 1000 Hz. The best relative threshold for base durations of 10, 25, and 60 msec, was found at 25 msec. When these CV‐like, noise‐buzz patterns were passed through a series of one‐third octave filters, some filter conditions yielded performance as good as with the entire spectrum, while some did not. The principal factor was the intensity difference between the noise and buzz energy in the particular one‐third octave band. We conclude that time‐marking information is not integrated across frequency bands, and that the temporal discrimination is controlled largely by temporal masking in that spectral region where masking is smallest. |
