Measurements and models for tone localization by moving listeners

Abstract

Listeners were given the challenging task of localizing a steady-state sine tone in a moderately reverberant room. Listeners attempted to optimize performance by moving during the nine-second tone interval. To discover listener localization strategies, the experiment acquired complete records of listener head motion (Polhemus head tracker) and the signals in the ear canals (Etymotic probe tubes). Experiment data were used to test two models of sound localization by moving listeners: According to the “Relative Null" model, listeners search for nulls in relevant interaural differences and use the momentary nose orientations where these nulls occur as indicators of source azimuth. According to the “Inferred Azimuth" model, listeners acquire a continuous, long-term record of inferred source location based on momentary head orientation combined with corresponding interaural differences. Models include different cue weighting assumptions and are evaluated by their ability to predict listener responses. The Relative Null model proves to be more accurate, but sometimes fails to make a prediction. The Inferred Azimuth model always makes multiple predictions, and often leads to further insights. These models are the most straightforward of numerous possibilities. Alternatives that weight the time course of listener cues, should be considered.