Directional hearing in the barn owl (Tyto alba)

Area of Science:

• Bioacoustics
• Auditory Neuroscience
• Animal Physiology

Background:

• The barn owl's external ear plays a crucial role in its exceptional hearing abilities.
• Understanding the acoustical properties of the owl's ear is key to deciphering its predatory success.

Purpose of the Study:

• To investigate the acoustical properties and directional sensitivity of the barn owl's external ear.
• To correlate external ear acoustics with neural auditory responses.

Main Methods:

• Sound pressure measurements in the ear canal and outer ear cavity.
• Recording of cochlear microphonic (CM) potentials from the round window membrane.
• Analysis of acoustic gain, pressure amplification, and directivity patterns.

Main Results:

• The external ear provides significant pressure amplification (up to 20 dB) between 3-9 kHz.
• Directional sensitivity increases above 5 kHz, with specific disparities in elevation and azimuth between ears.
• CM directivity patterns differ from external ear patterns and are lost above 10 kHz, exhibiting unique axial and directional planes.

Conclusions:

• The barn owl's external ear functions as a sophisticated acoustic filter and directional antenna.
• The asymmetrical shape and diffraction properties contribute to frequency-dependent directional sensitivity.
• Differences between external ear and CM directivity suggest neural processing plays a role in sound localization.