Sound Localization and Experience-Dependent Plasticity

Localizing sound sources in the external world requires the integration of multiple cues. The relative time of arrival and sound level across the two ears depend on which side of the head the sound originates from (azimuth) and frequency-dependent filtering by the head and ears that depends on the vertical angle of the sound source (elevation). For a given location these cues correspond, but not uniquely for a given frequency. Thus, information is integrated across different monaural and binaural cues and different frequency ranges. The correspondence of cue values also depends on individual’s head and outer ear (pinna) size and shape and the relative state of their hearing at each ear, all of which change with age. Possibly as a consequence, the calibration of these cues in the auditory system is quite flexible. Flexibility may also be an advantage for dealing with different acoustic environments.