Effects of temporal fringes on fundamental-frequency discrimination

It has recently been shown that the ability of listeners to encode the F0 of a "target" harmonic complex can be disrupted by another complex (the "fringe") presented immediately before and after it [R. P. Carlyon, J. Acoust. Soc. Am. 99, 525-533 (1996)]. This finding has been attributed to listeners overintegrating information about the fringe's F0 when estimating that of the target. Here difference limens for F0 (DLF0s) for a 100-ms harmonic complex target were measured using a two-interval two-alternative forced choice (2I-2AFC) adaptive procedure, in the presence and absence of 200-ms harmonic fringes. The target F0s in the signal and standard intervals were geometrically placed around a nominal F0 of 88 or 250 Hz; the fringe F0, constant throughout a block, was set at either of these two frequencies. The harmonics were bandpass filtered into one of three different frequency regions: low (125-625 Hz), mid (1375-1875 Hz), or high (3900-5400 Hz). In the low and mid regions, the fringes produced a large increase in DLF0s when they had a similar F0 to the target. This effect was absent or greatly reduced when the fringes and targets either had widely different F0s or occupied different frequency regions, and it was not reduced by providing additional spectral cues to the transition between fringes and targets. In the high region, the fringes produced large increases in DLF0s whether or not their F0 was similar to that of the targets. It is concluded that these results reflect a process of overintegration which, in the low and mid regions, is sensitive both to the F0 and to the spectral region of the stimuli. It is suggested that the different results in the high region may reflect the fact that, unlike in the low or mid regions, all the components of the targets and fringes were unresolved by the peripheral auditory system. Finally, the results of all the experiments are discussed in terms of auditory streaming.