The Influence of Phase on Tone Quality and Loudness; the Interference of Subjective Harmonics
Ernest K. Chapin, Floyd A. Firestone · The Journal of the Acoustical Society of America · 1934
A strong 108 cycle fundamental and one of its harmonics were impressed on one ear in various relative phases and sound pressures. The tone quality and the loudness of the combination were found to depend on the relative phase of the two components. In a certain phase relation the loudness of the combination was 3.5 db less than the loudness of the fundamental alone; varying the phase changed the loudness of the combination by about 10 db. The above observations may be explained by assuming that the ear mechanism distorts the pure components of a complex sound pressure, producing subjective harmonics which may either constructively or destructively interfere depending on the relative phases of the components. Some evidence was found in support of an assumption that the subjective harmonics due to a single low frequency pure tone actuating the ear, are in phase as cosine functions without epoch angles.