ENT Ear 29a34b1e Auditory fatigue is seen at A 90 dB, 4000Hz B 110 dB, 4000Hz C 130 dB, 4000Hz D 150 dB, 4000Hz High-Yield Explanation Auditory fatigue occurs at 90dB, 4000Hz. 90dB for 8hour a day for 5weeks is the maximum safe limit. (Ref: Diseases of EAR, NOSE AND THROAT by PL DHINGRA - 6th Edition)