Level discrimination of stop-consonant noise bursts: Performance in single- and two-interval tasks with single and multiple standards.

Abstract

Discrimination of increments in the rms level of either the initial or final consonant noise burst of the word (pæt/) was measured for seven highly trained, normal-hearing listeners. The stimulus was a single token of /pæt/ produced by a female talker and digitized at 20 kHz. The noise bursts’ sample points were multiplied by (1+k), 0.025≤k≤4.1, to obtain rms-level increments ranging from 0.2–14.0 dB. Experiment I (n=4) compared discrimination performance for noise bursts presented either ‘‘in isolation’’ (i.e., excerpted from the word) or in word context. A constant-stimulus 2IFC procedure was employed. Level discrimination thresholds expressed as 20 log (1+k) were 2.0–3.0 dB for both the /p/ and /t/ bursts ‘‘in isolation.’’ Thresholds ‘‘in context’’ were 2.0 dB for /t/ and 5.0–7.0 dB for /p/. Experiment II (n=3) compared level-discrimination performance measured in four different tasks for /p/ or /t/ bursts presented ‘‘in context.’’ The tasks were (a) 2IFC with a single standard (/pæt/); (b) 2IFC with three standards (/kæt, pæk, pæt/); (c) single interval, single standard; and (d) single interval, three standards. A strong context effect was again obtained with the /p/ burst, but the effects of task and number of standards were small. [Supported by OCAST Grant HSO-005 and Presbyterian Health Foundation.]