The effects of signal duration on NoSo and NoS pi thresholds at 500 Hz and4 kHz

A two-interval, two-alternative temporal forced-choice procedure was used t o measure NoSo and NoS pi masked thresholds with 500-Hz and 4-kHz tonal sig nals. The duration of the signal was either 10, 20, 40, or 320 ms. The mask ers were 200-Hz-wide bands of Gaussian noise centered at the frequency of t he signal and presented continuously. Decreasing the duration of the 500-Hz tonal signal resulted in a modest increase (1.5 dB or so) in the masking-l evel difference (MLD) measured between NoSo and NoS pi conditions. In contr ast, decreasing the duration of the 4-kHz tonal signal resulted in a substa ntial decrease (4.5 dB or so) in the MLD. Comparisons of the data with thre sholds predicted from analyses based on "windows of temporal integration" p rovided quantitatively acceptable accounts of the data. The data obtained i n the NoS pi condition at 4 kHz, which are novel and were of primary intere st, were well-accounted for in a statistical sense. However, there were sma ll, but systematic, discrepancies between the predictions and the data. Tho se discrepancies, although small in magnitude, suggest that binaural tempor al integration at high frequencies, where the envelopes of the stimuli conv ey the information, may be inherently different from both monaural temporal integration and binaural temporal integration at low frequencies. (C) 1999 Acoustical Society of America. [S0001-4966(99)05203-0].