Low frequency eardrum directionality in the barn owl induced by sound transmission through the interaural canal
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The middle ears of birds are typically connected by interaural cavities that form a cranial canal. Eardrums coupled in this manner may function as pressure difference receivers rather than pressure receivers. Hereby, the eardrum vibrations become inherently directional. The barn owl also has a large interaural canal, but its role in barn owl hearing and specifically in sound localization has been controversial so far. We discuss here existing data and the role of the interaural canal in this species and add a new dataset obtained by laser Doppler vibrometry in a free-field setting. Significant sound transmission across the interaural canal occurred at low frequencies. The sound transmission induces considerable eardrum directionality in a narrow band from 1.5 to 3.5 kHz. This is below the frequency range used by the barn owl for locating prey, but may conceivably be used for locating conspecific callers.
KeywordsHearing Auditory Barn owl Pressure difference receiver Sound localization Interaural canal
The authors thank S. Brill for technical assistance and logistical support and K.L. Willis and C.E. Carr for providing a 3D-reconstruction of the interaural canal. This work was supported by the Deutsche Forschungsgemeinschaft (Grant WA 606/20-2).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
The owls were treated and cared for in accordance with the guidelines of the “Landespräsidium für Natur, Umwelt und Verbraucherschutz Nordrhein-Westfalen, Recklinghausen, Germany”.
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