[The prognosis of the noise-induced permanent hearing-loss (author's transl)].

Basing on a microscopic study the question was explored whether a TTS is found in the high-frequency range after exposure to a low-frequency tone or not. Such a depression is demonstrable after several registrations with automatic audiometry. This depression is significantly higher in the average of normal-hearing persons than in noise-resistant men (having a normal threshold after working in noise for many years). Also after the exposure the spikes of the Békésy-audiogram are significantly smaller in the noise-resistant men than in the control-group. Paying attention to both parameters the significance is 1%. Therefore the investigation of the high-frequency-range after exposure to a low-frequency tone seems to be a method of prediction of PTS.