Detection of tones in masking noise:: Dependence of tone duration and masker level

The objective of this experiment was to examine masked thresholds and temporal integration at supra threshold levels by measuring thresholds for tones of different durations as a function of masker level for both normal-hearing and hearing-impaired listeners. Masked thresholds were measured for a 2-kHz tone at 8 different durations: 3, 6, 12, 24, 48, 96, 192 and 384ms, using an adaptive, three interval, three-alternative forced-choice procedure. Four different masker levels were used: 25, 45, 65 and 85 dB SPL for normal-hearing listeners, and 70, 80, 90 and 100 dB SPL for hearing-impaired listeners. Results for normal-hearing listeners show that the signal-to-masker ratio required to detect the tone varies nonmonotonically with masker level. Both the signal-to-masker ratio at threshold and the temporal integration shaw a significant increase at moderate masker levels. The hearing-impaired listeners showed less temporal integration than the normal-hearing listeners. For this group the signal-to-masker ratio at threshold increased with masker level for the shortest signal durations. The present data are discussed qualitatively in terms of earlier data and models of temporal integration and masked thresholds.