Abstract:
Detection thresholds were measured as a function of the temporal position
of a 5-ms sinusoidal signal presented within one of two 500-ms observation
intervals. Both intervals contained a 400-Hz-wide noise masker, logarithmically
centered at 2500 Hz, that was gated on at 150 ms and off at 350 ms within each
interval. The signal and masker were both gated with 2-ms linear ramps. The
level of the signal was tracked adaptively in blocks of forty 2I 2AFC trials to
estimate a 70.7% correct detection threshold. Thresholds were measured at 43
temporal signal positions within the observation interval, with detailed
sampling around the onset and offset of the masker to assess temporal edge
effects. Experiments to date with four listeners have focused on signals
presented at 1900 or 2100 Hz. The temporal microstructure of the detection
functions has characteristically revealed a complex pattern of under- and
over-shoot (i.e., enhanced and diminished detection, respectively). These
effects, which have been observed at both the onset and offset of the masker for
virtually all masker spectrum levels between N[inf 0]=0 and 70 dB, may
accentuate the temporal edges of the masker and, in general, enhance detection
of acoustic onsets and offsets.