The owl's interaural pathway is not involved in sound localization

Sound transmission through the barn owl's (Tyto alba) interaural pathway was measured by comparing the thresholds of single auditory neurons of the cochlear nucleus in response to independent stimulation of the ipsilateral and the contralateral ears. The interaural pathway acted as an acoustical low-pass filter. It attenuated sound by an average of 13 dB at 3.5 kHz, and by an average of 63 dB at 7.0 kHz under the experimental conditions used, as determined from single-unit thresholds. Sound pressure measurements in the middle ears confirmed the low-pass filter characteristics of the interaural pathway. Sound attenuation in the interaural pathway is too large to enable/the two ears to function as coupled pressure-difference receivers at the sound pressure levels and for the frequency range (6–8 kHz) important for sound localization by the owl.