Mechanisms of sound localization in the barn owl (Tyto alba)
- 974 Downloads
We investigated the mechanisms by which the barn owl (Tyto alba) determines the azimuth and elevation of a sound source. Our measure of localizing ability was the accuracy with which the owl oriented its head to a sound source.
When localizing tonal signals, the owl committed the smallest errors at frequencies between 4 and 8 kHz. The azimuthal component of these errors was frequency independent from 1 to 8 kHz, but the elevational component increased dramatically for frequencies below 4 kHz.
The owl's mean error when localizing wide band noise was nearly three times less than its mean error when localizing the optimal frequency for tonal localization (6 kHz).
Occluding the right ear caused the owl to orient below and to the left of the sound source; occluding the left ear caused it to orient above and to the right of the sound source.
With ruff feathers (facial ruff) removed, the owl continued to localize sounds accurately in azimuth, but failed to localize sounds in elevation.
We conclude from these results that the barn owl uses interaural comparisons of sound spectrum to determine the elevation of a sound source. Both interaural onset time and interaural spectrum are used to identify the azimuth of the sound source. If onset time is not available (as in a continuous sound), the owl can derive the azimuth of the source from interaural spectrum alone, but its spatial resolution is poorer.
KeywordsAzimuth Alba Wide Band Small Error Onset Time
Unable to display preview. Download preview PDF.
- Knudsen, E.I.: Sound localization in birds. In: Comparative studies of hearing in vertebrates. Popper, A.N., Fay, R.R. (eds.). New York: Springer (in press)Google Scholar
- Knudsen, E.I., Blasdel, G.G., Konishi, M.: Sound localization by the barn owlTyto alba measured with the search coil technique. J. Comp. Physiol.133, 1–11 (1979)Google Scholar
- Knudsen, E.I., Konishi, M.L.: Space and frequency are represented separately in the auditory midbrain of the owl. J. Neurophysiol.41, 870–884 (1978)Google Scholar
- Konishi, M.: Locatable and nonlocatable acoustic signals for barn owls. Am. Natl.107, 775–785 (1973a)Google Scholar
- Konishi, M.: How the owl tracks its prey. Am. Sci.61, 414–424 (1973b)Google Scholar
- Norberg, A.: Physical factors in directional hearing inAegolius funereus (Linné) (Strigiformes), with special reference to the significance of the asymmetry of the external ears. Arkiv. Zool.20, 181–204 (1968)Google Scholar
- Norberg, R.A.: Skull asymmetry, ear structure and function, and auditory localization in Tengmalm's owl,Aegolius funereus (Linné). Philos. Trans. R. Soc. Lond. (Biol.)282, 325–410 (1978)Google Scholar
- Payne, R.S.: Acoustic location of prey by barn owls (Tyto alba). J. Exp. Biol.54, 535–573 (1971)Google Scholar
- Pumphrey, R.J.: The sense organs of birds. Ibis90, 171–199 (1948)Google Scholar
- Robinson, D.A.: A method of measuring eye movement using a scleral search coil in a magnetic field. IEEE Trans. Biomed. Electron.10, 137–145 (1963)Google Scholar
- Searle, C.L., Braida, L.D., Davis, M.F., Colburn, H.S.: Model for auditory localization. J. Acoust. Soc. Am.60, 1164–1175 (1976)Google Scholar
- Woodworth, R.S.: Experimental Psychology, pp 349–361. New York: Holt, Rinehart and Winston 1962Google Scholar