To further test the hypothesis that periodicity pitch is mediated, at least peripherally. by neural fibers which ordinarily respond to high frequencies, the phenomenon of residual masking or short‐duration auditory fatigue was employed. Pure tones of 150 and 2200 cps, and a 2200‐cps signal pulsed 150 times per second all at several levels, were used in all combinations as fatigue and test stimuli. The results support the findings of Small and Campbell with respect to the masking of periodicity pitch. Perhaps the most interesting observation was that, if a pulse signal at moderate levels was used as the fatiguer, thresholds were shifted significantly for the 2000‐cps and pulsed signals, but were not shifted for the 150‐cps signal, even though pitch of the fatiguer corresponded to this frequency. Only when the level of the fatiguer was raised to 100 dB SPL, a level which almost certainly will give rise to nonlinear effects—i.e.—enveloped detection. did significant threshold shifts appear at the frequency of the pulse rate, 150 cps.