During 1960, the principal emphasis in audiology was on noise-induced hearing loss, newer hearing tests, recruitment, and pathologic adaptation.
Numerous reports were published on auditory fatigue (now called temporary threshold shift and abbreviated TTS) and on permanent hearing loss due to noise. From Ward's1 study, we conclude that any noise not intense enough to produce a measurable TTS does not contribute to the TTS or its recovery produced by a more intense noise. Ward2 also showed that when there is a 50 db., or more, TTS in normal ears, recovery during the first few minutes proceeds logarithmically with time and later it becomes linear with time.
Kylin3 tried to relate TTS and permanent hearing loss. He studied the relation between different octave bands of noise and their "potential damage risk" and applied this relation to 89 men who were exposed to intense flat noise for periods of