Abstracts of Articles from Bell System Sources

Loudness, Pitch and the Timbre of Musical Tones and Their Relation to the Intensity, the Frequency and the Overtone Structure.2 HARVEY FLETCHER. It is generally supposed t h a t the three psychological characteristics of a musical tone, namely, loudness, pitch and timbre, are each directly dependent upon the corresponding physical characteristics of the sound wave producing the tone, namely, intensity, frequency of vibration and overtone structure. In this paper it is shown t h a t each of the psychological characteristics is not dependent upon a single one b u t upon all three of the above mentioned physical characteristics. Quantitative measurements of these relationships have been made using a large number of observers. For example, it was found t h a t one tone may have the same pitch and loudness as another and yet have an intensity 100 times as great, the difference being due to the difference in the overtone structure; or two tones may have the same pitch and overtone structure and yet have frequencies of vibration t h a t differ as much as 5 per cent, the difference being due to the different intensity of the two tones. An empirical formula showing the dependence of loudness upon the three physical characteristics mentioned has been formulated although no such formula has been found for showing a similar relationship for pitch. Such a relationship is shown graphically for pure tones. Also some very marked effects upon 1 Proc. I. R. E., October, 1934. 2 Jour. Acous. Soc.