In noise-induced hearing loss, audiogram shows a typical notch at: (A) 1000 Hz, (B) 2000 Hz, (C) 3000 Hz, (D) 4000 Hz
Answer is D. Audiogram in NIHL shows a typical notch at 4000kHz, for both air and bone conduction. (Ref: Diseases of EAR, NOSE AND THROAT by PL DHINGRA - 6th Edition)