The role of head movements and vestibular and visual cues in sound localization.

In a previous paper the writer has demonstrated that a distinct localization of sound exists for directions which do not fall into the horizontal plane but lie above or below at varying elevations, in other words that a discrimination of directions with respect to above and below and front and back is possible as well as discrimination with respect to right and left which has been studied for many years. It was found that only a head movement during the presentation of the sound affords an adequate discrimination of sound direction in the dimension of above and below and thus makes localization complete. This is probably the reason why sound localization with respect to above and below has not been demonstrated in the laboratory at an earlier time. The paper referred to gives an analysis of the manner in which a complete perception of a sound direction is achieved with the help of a head movement. The binaural cues on which sound localiza1 The writer wishes to express his gratitude to Prof. W. Koehler and to Dr. Mary Henle for their help in preparing this manuscript. • Ueber die Wahrnehmung der Schallrichtung. Psychol. Forsch., 22, pp. 238-266 (I). A short English report on the same work has been published in the / . Acoust. Soc. Amer., 1939, pp. 270-74 (II). The two papers will be referred to as I and II respectively. In the present paper the writer has attempted to present the material in such a way that it can be understood without knowledge of the previous papers. While paper II lacks theoretical discussion it may be useful for a quick reference to previous experimental results.