Binaural processing in a multi-sound environment : the role of auditory grouping cues.
An important question in auditory research concerns the extent to which the perceptual
attributes of a sound source are invariant of the background against which that sound is
presented. The experiments reported herein examined the conditions under which the
perceived lateral position of a sound was influenced by the presence of other sounds, in
particular, the role of auditory grouping cues in segregating binaural information was
investigated. Two distinct sets of experiments were conducted. In the first, a
lateralisation-matching procedure was used which exploited the paradigm of Trahiotis and
Stern [C. Trahiotis and R. M. Stern, J. Acoust. Soc. Am. 86, 1285-1293 (1989)] to
investigate the influence of a spectrally flanking complex on the lateral position of a
perturbed harmonic. Three types of perturbation were considered: onset asynchrony
(Experiments 1 & 2), mistuning (Experiment 3) and frequency modulation (Experiment
4). It was found that even for relatively small perturbations the tone was perceived to be
in a different lateral position to the complex, with the influence of the flanking
components decreasing monotonically with increases in the size of the perturbation.
However, the complex still maintained a residual influence on the lateralisation of the
pure tone even for the largest asynchrony used (Experiment 5). Experiment 6 confirmed
that the lateralisation of the tonal complex was consistent with the aggregation of binaural
information across frequency. The second set of experiments used a signal detection
paradigm to investigate whether temporal context influences binaural processing.
Sequentially capturing an 800-Hz interferer tone into a separate perceptual stream to that
of a 400-Hz target significantly reduced the amount of binaural interference (Experiments
7 -9), although this result may have been mediated by peripheral rather than central
processes (Experiment 10). The implications of the results for models of auditory
processing of complex sounds are discussed.