In this report, the scaling of higher qualities of stereophonic sounds are treated. The concept of the quality treated here comprises of seven different characters; vividness, clearness, separation of each sound from numerous sound sources, separation of the signal from the noise, feeling of offensive reverberation, feeling of presence, and feeling of the distance of the sound source. At the beginning, the author made the listeners clarify, unify, and fix the concept of the quality in their psychological domains following careful procedure, and then gave stimulative sounds to them and demanded them to make comparative judgements to the sounds. The stimulative sounds comprised of seven varieties-a 2 channel reproduction, a 1 channel 2 speaker reproduction, and five mixed 2 speaker reproductions. The word "mixed reproduction" here means that the reproduced signals are obtained by artificially making the 2 channels mutually cross-talk by the same amount to one another. The mixing level is defined as the power ratio of the cross-talk signal to the original signal, the mixing levels employed here being 13, 8, 5, 4, and 3 db. "The method of paired comparison" is employed in the experiment, and the results are calculated by Thurstone's method (case III). As a result, the seven scales in each qualities are obtained. These scales indicate the degree to which the stereophonic sounds stood at advantage over the usual 1 channel reproductions by the distance on the psychological scales. For example, on the "vividness scale", we can see that the "2 channel" reproduction is ranked as the most vivid, the "3 db mixing" as the least vivid, with the "1 channel" reproduction intermediate between them. The psychologically evaluated distance from "1 channel" to "2 channel" is about 1. 3. These scales are useful not only in evaluating the qualities of the reproduction systems by the distances between the reproduction systems on each quality scale, but also in obtaining quantitative relation between the qualities by counting the correlation factors between the scales. The details will be given in succeeding reports.
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