The Simulated Open Field Environment for Auditory Localization Research

E. Hafter and B. Seeber
Auditory Perception Lab, 
Department of Psychology
University of California at Berkeley, 
Berkeley, CA 94720-1650


To date, most research on auditory localization has been done in either
a non-reverberant environment or in virtual acoustic space. Whereas the
anechoic environment represents an unnatural listening condition, head
movements can have an impact on studies with virtual acoustics. The
Simulated Open Field Environment (SOFE) uses computer controlled
loudspeakers in an anechoic chamber to create realistic auditory scenes
with simulated sources and echoes. It has been reimplemented using 48
channels of parallel audio. In addition, a projected high-resolution
visual scene of 100º allows for study of relations between hearing and
vision. Localization responses of the subject can be captured through a
moving visual pointer represented by a simple light spot on the visual
scene or by pictures of e.g. speakers at various azimuths or distances.

By moving this pointer object indirectly with a trackball the
localization responses are decoupled from proprioceptive information.
Use of such a large number of speakers allows direct open-field
simulations of primary sounds as well as a limited number of reflection
and additional reflections can be simulated by amplitude panning
between speakers. Distance-dependent damping as well as temporal delay
is simulated for all auditory signals - sources and reflections - with
regard to the positioning in the projected visual scene. With the
option of tracking head movements, the new SOFE's most important
advantage is to allow for study of sound localization in a controlled
reverberant environment without the need for a defined head-position.
Studies to be discussed include inclusion studies of adaptation to
reverberant environments, visual capture in localization and
localization of cochlear-implant patients in reverberant environments.