Intracranial lateralization bias observed in the presence of symmetrical hearing thresholds.

Matthew J Goupell,Virginia Best,H Steven Colburn

doi:10.1121/10.0006720

Abstract

It is generally assumed that listeners with normal audiograms have relatively symmetric hearing, and more specifically that diotic stimuli (having zero interaural differences) are heard as centered in the head. While measuring intracranial lateralization with a visual pointing task for tones and 50-Hz-wide narrowband noises from 300 to 700 Hz, examples of systematic and large (>50% from midline to the ear) lateralization biases were found. In a group of ten listeners, five showed consistent lateralization bias to the right or left side at all or a subset of frequencies. Asymmetries in hearing, not apparent in audiometric thresholds, may explain these lateralization biases.

Highlights

When a sound source is directly in front of or behind a listener, and is equidistant to the two ears, the sound reaching the ears will have zero interaural time difference (ITD) and interaural level difference (ILD)
It is generally assumed that the combination of zero ITD and ILD is mapped to the center of the acoustic reference system and is perceived as
This idea is broadly supported by dichotic listening experiments, in which stimuli are presented over headphones such that ITD and ILD can be manipulated systematically

Summary

Introduction

When a sound source is directly in front of or behind a listener, and is equidistant to the two ears, the sound reaching the ears will have zero interaural time difference (ITD) and interaural level difference (ILD). It is generally assumed that the combination of zero ITD and ILD is mapped to the center of the acoustic reference system and is perceived as “centered” by the listener. This idea is broadly supported by dichotic listening experiments, in which stimuli are presented over headphones such that ITD and ILD can be manipulated systematically. Here we report that an intracranial lateralization bias can occur for listeners with symmetrical thresholds in the range of normal hearing, and without evidence that it is caused by the experimental equipment

Methods

Results

Conclusion