Objective Allocation of Sound Image from Binaural Stimulation
Yoshimitsu Kikuchi · The Journal of the Acoustical Society of America · 1956
As is well known, in the case of a sensation stimulated with binaural earphones, the location of the sound image inside one's head is done by subjective judgment. Now I would propose a new conception, i.e., an “objective position” of sound image. In order to realize this “objective allocation,” I have inaugurated two methods as follows: (1) The “Null Method”: If the binaural earphone circuit is momentarily reversed—thus interchanging right and left sides—, the subject then perceives the image rapidly moving to a new position. The closer the physical position of the sound source is to the exact center, the less will be the image movement. The sensation of this image movement is so very sharp that a minute movement can be perceived. The image position at the “adjustment of no-movement” or at “nullity,” is determined with much smaller individual and group errors than by the well-known subjective-center method. Accordingly, the image position at which there is no movement can be considered an “objective center.” (2) The “Comparative Sensation Method”: This consists of a comparison of the image-position of the sound being tested with that of a pilot-signal—with a controllable phase-difference—introduced into each ear. This sensation is also very sharp, and the image position coinciding with the pilot signal image can be considered an “objective position.”