Localizing where a sound is coming from is an important component of human auditory perception, and, for example, provides a listener with the ability to maintain awareness of events outside the visual field, or to isolate one voice among many in a crowded room. Information about the left/right location of a sound source is provided by the differences of time-of-arrival and sound level between the signals reaching the left and right ears. However, these between-ear differences are insufficient to specify front/rear location or up/down location. Some information about those dimensions can be provided through the outer ears' direction-dependent filtering, but a listener can take a more active role in localization by moving the head: Dynamic information is provided by the relation between head motion and the resulting changes in inter-aural differences.
With support of the National Science Foundation, Dr. Ewan Macpherson will investigate the effectiveness of the information provided by head motion, and the way it interacts with other information about sound location. Normal-hearing listeners will attempt to localize real and synthesized sound sources, both while the head is stationary and while the head is in motion. The project will extend knowledge of listeners' use of dynamic cues for vertical-plane localization. Dr. Macpherson will also use a novel experimental head-movement paradigm, which will permit detailed examination of the interplay of static and dynamic information. This project will facilitate the integration of research and education by involving undergraduate students as partners in the laboratory. New equipment acquired and software developed to carry out the project will greatly enhance the research capabilities at the Kresge Hearing Research Institute at the University of Michigan.
