Changes in Pitch of Tones of Low Frequency as a Function of the Pattern of Excitation Produced by a Band of Noise

Abstract

The excitation pattern of a tone is markedly altered by a masking stimulus. It should be expected that the pitch of the masked tone, as well as its threshold and its loudness, would be affected. In the present investigation the effect of a narrow band of noise (90 c.p.s. wide, centered at 410 c.p.s.) upon the pitch of pure tones of low frequency was measured in a series of experiments. Subjects matched the pitch of a tone heard in the presence of a band of noise to the pitch of a tone heard alone. These two tones, one partially masked and the other not, were presented to the subject in repeated succession. The listener first matched these tones for loudness. He then adjusted the frequency of the unmasked tone until it was the same in pitch as the masked tone. The pitch change was investigated at a number of frequencies and of loudness levels. Systematic changes in pitch were observed. The presence of the noise raises the pitch of a partially masked tone whose frequency is immediately above those of the band of noise. This change in pitch occurs even though the intensity of the masked tone is greater than that of the unmasked tone. In contrast, the presence of the masking noise lowers the pitch of a tone whose frequency is just lower than those of the band of noise, but this change is largely accounted for in terms of the intensity difference required for an equal loudness match. An attempt is made to account for the changes in pitch in terms of a place theory.