Fast processing explains the effect of sound reflection on binaural unmasking

TL;DR

This study investigates how sound reflections and reverberation influence binaural unmasking and detection of tones in noise, revealing that early reflections can improve detection while late reflections can hinder it, explained by a new binaural model.

Contribution

It introduces a binaural model with a sluggishness component that better predicts the effects of reflections on sound detection in reverberant environments.

Findings

Early reflections improve detection thresholds for frontal sources.

Late reflections as late as 150 ms reduce detection thresholds.

The proposed model outperforms traditional models in predicting results.

Abstract

Sound reflections and late reverberation alter energetic and binaural cues of a target source, thereby affecting it's detection in noise. Two experiments investigated detection of harmonic complex tones, centered around 500 Hz, in noise in a virtual room with different modifications of simulated room impulse responses (RIR). Stimuli were auralized using the SOFE's loudspeakers in anechoic space. The target was presented from the front or at 0$^\circ$ azimuth, while an anechoic noise masker was simultaneously presented at 0$^\circ$. In the first experiment, early reflections were progressively added to the RIR and detection thresholds of the reverberant target were measured. For a frontal sound source, detection thresholds decreased while adding the first 45 ms of early reflections, whereas for a lateral sound source thresholds remained constant. In the second experiment, early reflections were cut out while late reflections were kept along with the direct sound. Results for a target at 0$^\circ$ show that even reflections as late as 150 ms reduce detection thresholds compared to only the direct sound. A binaural model with a sluggishness component following the computation of binaural unmasking in short windows predicts measured and literature results better than when large windows are used.