STUDIES ON CENTRAL FACTORS IN HEARING (the 3 rd Report)

Abstract

We experience a sport-like sound image corresponding to a line-or a plane-shaped sound sources. Searching for the relationship of this phenomenon to the direction perception, the author established the following.When a point-shaped sound source is in a circular motion at various speeds in a frontal plane at a frontal distance of 1 meter, the sound image changes discontinuously in 6 stages with the increase of speed : (I) a circle at the lowest speed range, (II) an ellipse with reduced vertical axes, (III) an ellipse with redused vertical and horizontal axes, (IV) two glittering points right and left, (V) linear motion between two points, (IV) a fixed point. With variation in the direction or the distance of the sound source or the kind of the motion, various characteristic features are observed.The mono-and bin-aural sound images are quite similar on the side, but unlike in other directions. The qualitative different sound images are heared monoanraly according to whether the sound source takes place in front, on the side, at the back or on the upside, and binauraly according to whether it takes place in front, at the back or on the upside. The feature of the binaural sound image seemes to be that the monoaural ones are modified chiefly by the function of the association and commisure paths in the cortex of the brain. When a sound source is in a circular motion in the horizontal plane around the head, there is a stage that the direction of the motion of the sound image becomes reverse. Perhaps itchiefly depends on the relation between the angular velocity and the speed of sound. There is the time required to perceive the direction. About the various characteristic features of the sound images a concept of the subjective coordinates is a subject for consideration.