Temporary Threshold Shift from Octave-Band Noise: Applications to Damage-Risk Criteria

The growth and recovery of TTS in normal observers following exposure to octave-band noise is shown to follow the same course as that after broad-band noise: both are linear in log time. Rate of growth varies with frequency of exposure band and test frequency, being greatest at 4 kc following exposure to 2400–4800 cps or 1200–2400 cps, less at lower test frequencies and octave bands. The time for total recovery apparently is a function of the initial TTS. The results support present damage-risk criteria for continuous noise, which (1) suggest ear protection when octave-band levels exceed 85 db SPL and (2) require it in levels above 95 db SPL.