Auditory Azimuthal Localization Performance in Water as a Function of Prior Exposure

Objective: We report two psychoacoustical experiments that assessed the relationship between auditory azimuthal localization performance in water and duration of prior exposure to the milieu. Background: The adaptability of spatial hearing abilities has been demonstrated in air for both active and passive exposures to altered localization cues. Adaptability occurred faster and was more complete for elevation perception than for azimuth perception. In water, spatial hearing is believed to solely rely on smaller than normal cues-to-azimuth: interaural time differences. This should produce a medial bias in localization judgments toward the center of the horizontal plane, unless the listeners have adapted to the environment. Method: Azimuthal localization performance was measured in seawater for eight azimuthal directions of a low-frequency (<500 Hz) auditory target. Seventeen participants performed a forced-choice task in Experiment 1. Twenty-eight other participants performed a pointing task in Experiment 2. Results: In both experiments we observed poor front/back discrimination but accurate left/right discrimination, regardless of prior exposure. A medial bias was found in azimuth perception, whose size decreased as the exposure duration of the participant increased. Conclusion: The study resembles earlier results showing that passive exposure to altered azimuth cues elicits the adaptability of internal audio-spatial maps, that is, the behavioral plasticity of spatial hearing abilities. Application: Studies of the adaptability of the auditory system to altered spatial information may yield practical implications for scuba divers, hearing-impaired listeners with reduced sensitivity to spatial cues, and various normal-hearing users of virtual auditory displays.