Where versus what: The relationship between speech understanding and auditory motion processing

Abstract

Most sounds involve motion, either because the sound source moves, or the listener does. Thus, perceiving moving sounds is critical for listeners' functional ability to navigate auditory environments. Studies to date focused on the limits of sound motion detection. By contrast, we are interested in the functional importance of auditory motion perception and aim to understand which acoustic cues govern listeners' classification of sound motion. In the present study, we hypothesized that auditory motion perception is influenced by the extent to which stimuli are perceived as intelligible. Utilizing Chimaera compositions of speech and spectrally matched noise tokens, we varied the envelope type and number of frequency channels of acoustic stimuli, manipulating speech intelligibility. Stimuli were presented in free field as stationary or moving. Normal-hearing adults judged sound motion in a 2-AFC task, and verbally repeated what they understood. Results show that a speech signal envelope biased sound motion judgments to be stationary, and increasing speech intelligibility further increased bias. This suggests that speech intelligibility influences auditory motion perception, and that sound motion and speech may not be processed simultaneously. [Work supported by NIH-NIDCD(R01DC8083), NIH-NICHD (U54HD090256) and ASA's Hunt Fellowship.]