Phase and the Hearing - Impaired

Although Helmholtz, on the basis of experiments with 8-component harmonic complexes of fundamental frequencies near 119 and 238 Hz, claimed to "have never experienced the slightest difference in the quality of tone" with changes in relative phase among the components (Helmholtz, 1954), more recent studies have modified his conclusions (e.g., Mathes and Miller, 1947; Goldstein, 1967). It is now apparent that the primary determinant of the perceptibility of a given phase change is the frequency spacing between the sound's constituent sinusoidal components. When relative phase changes are made in components that are "close enough" together, they are perceptible; when they are made to widely spaced components, they are not. Phase sensitivity is thus understood to reflect the failure of frequency resolution only when a sound's constituent sinusoids interact (i.e., lie sufficiently within a single critical band, or auditory filter) will a phase change be detectable. (For a discussion of other factors, see Rosen, 1986).