Interaural Coherence Across Frequency Channels Accounts for Binaural Detection in Complex Maskers

Differences in interaural phase configuration between a target and a masker can lead to substantial binaural unmasking. This effect is decreased for masking noise having an interaural time difference (ITD). Adding a second noise with the opposite ITD further reduces binaural unmasking. Thus far, simulation of the detection threshold required both a mechanism for internal ITD compensation and an increased binaural processing 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 and 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 is moot when the masker coherence is constant across frequency bands. Combined with a monaural energy discrimination pathway, the model predicts the differences between single- and double-delayed noise, as well as four other data sets. It can help resolving the inconsistency that simulation of some data sets requires wide filters while others require narrow filters.