[RWebb]

check out the ear tufts...

here are a few tidbits for you:


Localization of Sound Sources

[1] phase differences between 2 ears (time-delay or differences in time of arrival) -- slight turns of head enhance this effect -- behavioral "tuning" of physiological system

[2] relative intensity differences between 2 ears -- "shading" by head, etc.

Konishi has done most of the work on sound localization by owls.

Common Barn Owl can resolve 1o in both horizontal and vertical planes; can also determine direction and speed of movement of an object, e.g. mouse.

Humans are about as good in the horizontal plane but only good to about 3o in the vertical plane.

Resolution in the vertical plane is enhanced by asymetrical ear openings and troughs formed by the facial ruff of feathers.

Left ruff faces downward, increasing sensitivity to sounds below the horizontal, and right ruff faces upward. Owl can tilt its head until the intensities are equalized, degree of tilt tells it at what vertical angle the source is located.

Facial ruff acts to collect and channel sound waves above 3 kHz which contains the greatest vertical time delay.

Low frequency sound is subject to greatest horizontal time delay -- removal of the ruff reduces vertical resolution, but not horizontal resolution.

Barn Owls also have specialized neurons that are highly sensitive to time delays of 40 to 100 msec (corresponding to 10 to 25 kHz).