The contribution of interaural time and level differences to the precedence effect at high frequencies

Abstract

The precedence effect (PE) allows us to locate sound sources correctly in rooms despite the presence of interfering reflections. It has been shown to function at high frequencies with highly modulated stimuli. These studies were done in the free-field where interaural time (ITDs) and level (ILDs) differences are in their natural combination. The present study investigated the relative contribution of ILDs and ITDs to the PE with high-frequency zero-phase harmonic complex tones. A localization dominance task was used in which participants indicated the location of the lead-lag stimuli and judged if sounds were perceived as fused. A preliminary analysis indicates that the PE emerged when either ITDs or ILDs were applied to lead and lag stimuli while the other binaural cue was held at zero. Patterns for localization dominance and fusion were nearly identical for ITD and ILD conditions, suggesting that ITDs and ILDs were equally effective for these highly modulated stimuli. Fusion of lead and lag extended to somewhat longer delays with smaller cue magnitudes, i.e. the more binaural cues differed between lead and lag the more likely they were to be segregated. The results support the idea that PE mechanisms are similar for ITDs and ILDs.