Fatigue effects of a pure tone and pure tones

Subjects with normal hearing were exposed to moderate intensity of a pure tone and pure tones. Exposure frequency consisted of: a single tone, 1500 Hz; two tones, 1500 and 2000 Hz; and three tones, 1500, 2000, and 3000 Hz. Fatigue effect measurements were made by automatic audiometry immediately after exposure. The greatest fatigue at frequencies 1/2–1 oct above an exposure frequency of 1500 Hz was shown by a single tone, the least effect by three tones, and the intermediate effect by two tones. The fatigue effects at the remote high frequencies were in the reverse order. These findings may be explained on the basis of harmonics and combination tones arising in the ear on stimulation with tones.