Prolonged exposure to noise levels greater than the following can impair hearing permanently:: (A) 40 decibels, (B) 85 decibels, (C) 100 decibels, (D) 140 decibels
Answer is C. A noise of 90 dB SPL, 8 hours a day for 5 days per week is the maximum safe limit as recommended by ministry of labour, govt of India-rules under factories act.