Context-Dependent Trading of Binaural Spatial Cues in Virtual Reality
Moore, Travis M.
The human auditory system locates sound sources in the horizontal plane using differences in the interaural arrival time and intensity level of the signal (ITD and ILD, respectively). Because these two cues are the primary inputs used to encode azimuthal auditory space, it is important to understand the nature of their relationship. Psychophysical studies have classically quantified cue weighting by the ratio of the ITD, in µs, needed to bring a fixed, eccentric intracranial percept, elicited by an ILD, back to midline (and vice versa). Termed the trading ratio (TR), this measure has been revealed to favor differentially the adjusted cue. Currently, the mechanisms behind the cue-dependency of the TR are poorly understood. The current study investigated whether localization adaptation, an auditory effect that causes a shift in the perceived laterality of one signal associated with another signal in time, accounts for the differential TRs. Three experiments revealed that (1) adaptive effects can occur using parameters classically used to measure the TR, (2) a task immune to adaptive effects yields a TR similar that observed when adjusting the ILD, and (3) adapting trains influence TRs in such a way that suggests the ITD contributes most to the TR during adjustment, and that adjusting the ILD results in a TR that reflects contributions from both the ITD and ILD.