ability of man and animals to determine the direction from which a sound is coming. This ability is dependent on the presence in them of two sound receivers—ears. A sound reaches the ear facing the source by a shorter route; therefore, the sound waves in both auditory canals are differentiated by the phase (time of arrival of a given phase) and amplitude (force) of the acoustic oscillations. A sound of different pitch is perceived in different ways: for low-pitched sounds (up to 1,500 oscillations per second), the direction to the sound-emitting body is determined the most precisely and almost entirely by the difference in time of arrival of the given phase of the acoustic oscillations; for high-pitched sounds, in which the difference in intensity of the sound between the right and left ears plays an important role, the determination is less precise. The difference in phase and intensity of the sounds perceived results in a differentiation of the impulses reaching the central nervous system from the right and left ears; this makes it possible to determine the direction of a sound.
A person with normal hearing can determine the direction of a sound in a horizontal plane accurate to within 3°. The location of a source in terms of height is determined less accurately. A change in position of the auricles (in animals) and head (in animals and man) helps to determine more accurately the direction from which a sound is coming. The binaural effect can be strengthened by increasing the distance between the receivers; this is done with sound locators.
REFERENCESRzhevkin, S. N. Slukh i rech’ ν svete sovremennykh fizicheskikh issledovanii, 2nd ed. Moscow-Leningrad, 1936.
Andreev, L. A. Fiziologiia organov chuvstv. Moscow, 1941.
Andreev, N. N. “Ob organakh slukha u nasekomykh.” In Problemy fiziologicheskoi akustiki, vol. 3. Moscow, 1955.