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An Investigation of Subjective Tones by Means of the Steady Tone Phase Effect

1937; Acoustical Society of America; Volume: 8; Issue: 3_Supplement Linguagem: Inglês

10.1121/1.1901997

1520-9024

John D. Trimmer, F. A. Firestone,

Noise Effects and Management

An observer listens with one ear to a combination of two pure tones. One is a loud 100-cycle tone, the other is a weaker 200-cycle tone. A phase relation between the two tones can be found such that the loudness of the two tones together is about one decibel less than the loudness of the fundamental alone. This is an example of the steady tone phase effect, in which a fundamental and one of its harmonics are heard together, the phase relation between the tones, as well as the pressure level of the harmonic, being subject to arbitrary control by the observer. This effect was studied with a fundamental of 100 cycles kept at a sound pressure level of 104 db above 0.0002 dyne/cm2. Harmonics up to the fifth were used, with particular emphasis on the second and third. Measurements of the phase of the harmonic sound pressure giving minimum loudness averaged approximately 180° for the second harmonic and 0° for the third (epoch angle of cosine functions relative to fundamental). Loudness measurements at these phase settings showed the loudness of the combined fundamental and harmonic to be about 1 db less than that of the fundamental alone. 180° from the phase of minimum loudness the loudness of the combined tones was about 1 db greater than that of the fundamental alone. The variation of quality with phase relation was also studied. Interesting variations between observers were investigated and attributed partly to psychological and physiological differences in individuals. But consideration of all the data obtained points to the conclusion, supported by theory, that the phase effect is a more complicated phenomenon than has commonly been assumed. Since this effect has been the basis for many studies of subjective tones, the concept of subjective tones is analyzed and interpreted in a new light.