Lower Interaural Coherence in Off-Signal Bands Impairs Binaural Detection

TL;DR

This paper presents a multi-channel model explaining how reduced interaural coherence in off-frequency regions impairs binaural detection, accounting for various experimental findings without requiring wider binaural filters.

Contribution

It introduces a novel incoherence interference mechanism based on interaural coherence, providing a unified explanation for binaural detection thresholds across different conditions.

Findings

Model accurately predicts detection thresholds for various noise configurations.

Incoherence interference explains data previously attributed to filter width differences.

The approach reconciles conflicting data sets with a single mechanism.

Abstract

Differences in interaural phase configuration between a target and a masker can lead to substantial binaural unmasking. This effect is decreased for masking noises with an interaural time difference (ITD). Adding a second noise with an opposing ITD in most cases further reduces binaural unmasking. Thus far, modeling of these detection thresholds required both a mechanism for internal ITD compensation and an increased binaural bandwidth. An alternative explanation for the reduction is that unmasking is impaired by the lower interaural coherence in off-frequency regions caused by the second masker (Marquardt & McAlpine, 2009, JASA pp. EL177 - EL182). Based on this hypothesis, the current work proposes a quantitative multi-channel model using monaurally derived peripheral filter bandwidths and an across-channel incoherence interference mechanism. This mechanism differs from wider filters since it has no effect when the masker coherence is constant across frequency bands. Combined with a monaural energy discrimination pathway, the model predicts the differences between a single delayed noise and two opposingly delayed noises, as well as four other data sets. It helps resolve the inconsistency explaining some data sets requires wide filters while others require narrow filters.