Observer weighting of monaural level information in a pair of tone pulses

A correlational analysis was used to assess the relative weight given to th e levels of two monaurally presented tone pulses for interpulse intervals ( IPIs) ranging from 2-256 ms. In three different experimental conditions, li steners were instructed to discriminate the level of the first pulse, the l evel of the second pulse, or the difference between the levels of the two p ulses. The level of the target pulse was chosen randomly and independently from trial to trial from a Gaussian distribution. The level of the nontarge t pulse was either fixed at 75 dB SPL or varied in the same manner as the l evel of the target. In the tasks in which one pulse was to be ignored, list eners gave increasing weight to the nontarget component as IPI decreased. L isteners weighted the level information in the pulses appropriately only wh en the IPI approached 256 ms. When the listeners were instructed to compare the pulse levels to one another, two of three listeners weighted the level s optimally at all IPIs, while the third listener did so only at the longes t IPI. For the two listeners who weighted the pulses optimally, a minimum i n performance was achieved at IPIs around 16-32 ms. Intensity discriminatio n thresholds were also measured for one pulse in the presence of a second f ixed pulse for IPIs of 2-256 ms. Thresholds were higher in all the two-puls e conditions relative to a one-pulse condition, and were dependent on the l evel of the nontarget pulse but not on IPI. The results indicate that level information is integrated to some extent over fairly long durations, but n ot in a manner that is consistent with simple temporal integration. (C) 200 0 Acoustical Society of America. [S0001-4966(00)02506-6].