Precedence effect for specular and diffuse reflections

Florian Wendt,Robert Höldrich

doi:10.1051/aacus/2020027

Abstract

Studies on the precedence effect are typically conducted by presenting two identical sounds simulating direct sound and specular reflection. However, when a sound is reflected from irregular surface, it is redirect into many directions resulting in directional and temporal diffusion. This contribution introduces a simulation of Lambertian diffusing reflections. The perceptual influences of diffusion are studied in a listening experiment; echo thresholds and masked thresholds of specular and diffuse reflections are measured. Results show that diffusion makes the reflections more easily detectable than specular reflections of the same total energy. Indications are found that this mainly due to temporal diffusion, while the directional diffusion has little effect. Accordingly, the modeling of the echo thresholds is achieved by a temporal alignment of the experimental data based on the energy centroid of reflection responses. For the modeling of masked threshold the temporal masking pattern for forward masking is taken into account.

Highlights

The precedence effect refers to a group of perceptual phenomena which allow us to localize sound sources in challenging reverberant environments
In a constellation of sound source, receiver, and reflective wall the distance traveled by the reflection determines not just the delay DT, and the inverse-square law intensity difference DL of the reflection compared to the direct sound
Masked threshold levels are below echo threshold levels with differences agreeing with literature [21]

Summary

Introduction

The precedence effect refers to a group of perceptual phenomena which allow us to localize sound sources in challenging reverberant environments. As the delay slightly exceeds the limits for summing localization the precedence effect becomes active In this range the auditory system suppresses localization cues carried by reflections and the leading direct sound dominates the perceived location of a single auditory image. Another increase of the delay yields widening of the auditory image until it breaks apart at the upper limit of echo suppression. At this transition, the so-called echo threshold the reflection becomes audible as a second auditory image. This threshold is especially relevant because it can be used to determine the strength of

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