Intensity discrimination of Gaussian-windowed tones: Indications for the shape of the auditory frequency-time window

The just-noticeable difference in intensity jnd(I) was measured for 1-kHz t ones with a Gaussian-shaped envelope as a function of their spectre-tempora l shape. The stimuli, with constant energy and a constant product of bandwi dth and duration, ranged from a long-duration narrow-band "tone" to a short -duration broadband "click." The jnd(I) was measured in three normal-hearin g listeners at sensation levels of 0, 10, 20, and 30 dB in 35 dB(A) SPL pin k noise. At intermediate sensation levels, jnd(I) depends on the spectre-te mporal shape: at the extreme shapes (tones and clicks), intensity discrimin ation performance is best, whereas at intermediate shapes the jnd(I) is lar ger. Similar results are observed at a higher overall sound level, and at a higher carrier frequency. The maximum jnd(I) is observed for stimuli with an effective bandwidth of about 1/3 octave and an effective duration of 4 m s at 1 kHz (1 ms at 4 kHz). A generalized multiple-window model is proposed that assumes that the spectre-temporal domain is partitioned into "interna l" auditory frequency-time windows. The model predicts that intensity discr imination thresholds depend upon the number of windows excited by a signal: jnd(I) is largest for stimuli covering one window. (C) 1999 Acoustical Soc iety of America. [S0001-4966(99)00306-9].