When arbitrary noises at the two ears are correlated,a single noise image is perceived inside the head even if a short interaural interval (IAI) is introduced.This study examined whether this binaural grouping is affected by the acoustic spectrum at various short IAIs.Psychophysical results show that the mean duration threshold across human participants for detecting a break in correlation (BIC) in binaurally identical noises was about 7 ms when the noise was of either wideband or low-frequency (￡ 400 Hz) narrowband,and was dramatically elevated when the center frequency of narrowband noise was increased.Moreover,although the perceptual fusion was maintained,the threshold was also elevated with the increase of the IAI from 0 to 4 ms.The IAI-induced threshold elevation was much larger for high-frequency narrowband noises than for low-frequency narrowband noises.Neurophysiological results show that the early cortical components of scalp event-related potentials to the BIC were markedly modulated by both center frequency and IAI.Thus,even when the perceptual fusion is maintained,the temporal storage of acoustic fine-structure details goes through a fast,frcquency-dependent decay.