Abstract
The barn owl (Tyto alba) is a nocturnal predator with excellent spatial hearing. My talk addresses two aspects of sound localization in this auditory specialist.
I. Binaural correlation
In order to use a binaural difference cue, the sound from a source
that enters the left ear must be compared with sound the the same source that enters the right ear. This results in the perception of a single auditory image; this process is known as binaural fusion. One feature of sound that is important to fusion is the degree to which the sounds arriving at the two ears are correlated. The ability of both barn owls and humans to localize based on ITD is eliminated if binaural correlation is reduced to zero. However, I show that barn owls can extract the ILD of a binaurally uncorrelated signal, and use that ILD to control an auditory saccade.
II. Spectral localization
Barn owls have been shown to use interaural time differences and
interaural level differences to localize the sources of sounds. Many
mammals, including humans, also exploit a monaural sound localization cue based on the location- and frequency-dependent filtering of the
pinnae and head. Recent measurements have shown that spectral features
similar to those in humans also exist in barn owls. I show that radical changes in monaural spectra that do not produce concomitant changes in the binaural difference spectrum have no effect on barn owl sound localization behavior.