Bi-coordinate sound localization by the barn owl

1. Binaurally time-shifted and intensity-unbalanced noise, delivered through earphones, induced owls to respond with a head-orienting behavior similar to that which occurs to free field auditory stimuli. 2. Owls derived the azimuthal and elevational coordinates of a sound from a combination of interaural time difference (ITD) and interaural intensity difference (IID). 3. IID and ITD each contained information about the azimuth and elevation of the signal. Thus, IID and ITD formed a coordinate system in which the axes were non-orthogonal. 4. ITD was a strong determinant of azimuth, and IID was a strong determinant of elevation, of elicited head turn.