Localization in simulated reverberant space using cochlear implants and hearing aids

Bernhard U. Seeber and Ervin Hafter


The Simulated Open Field Environment (SOFE) creates realistic auditory scenes with simulated
sources and echos inside an anechoic chamber. By playing sources and echoes from 48
horizontally arranged loudspeakers the subject is unencumbered by headphones and listens in the
free-field through their own, "perfect" head-related transfer functions. This allows us to directly
compare the results from normal hearing subjects against results from subjects with a hearing aid or
a cochlear implant. To provide localization feedback the subject can move an object in a projected
visual scene horizontally, vertically or in the distance. 

A working affiliation with the Douglas Grant Cochlear Implant Center at U.C. San Francisco will soon
allow for patients with bilateral CIs to be brought into the SOFE for studies of the impact of
reverberation on localization ability. Seeber and Fastl (DAGA '04) have
shown that the localization ability of a tested CI-patient was fully based on the evaluation
of interaural level cues (ILDs). Thus we suppose that CI-patients do not show
the precedence effect, i.e. the suppression of the echo for localization. Instead we assume that the
localized direction is determined by the ILD-sum of source and echo which would lead to a shift
towards the direction of the echo. 

In the talk we will introduce the new SOFE for studies with and without hearing devices. Initial
results from localization studies with CI-patients will be shown. The talk will be held in German.