As per the Environment Protection Act, 1986, what are the permitted noise limits (in decibel) for the silence zone during day time and night time?
- A50 and 60, respectively
- B40 and 30, respectively
- C50 and 40, respectivelyCorrect
- D60 and 50, respectively
Solution
Concept
The ambient noise limit for a silence zone is 50 dB(A) by day and 40 dB(A) by night.
Step-by-step solution
1. Ambient noise standards are given in the Noise Pollution (Regulation and Control) Rules, 2000, made under the Environment Protection Act, 1986. 2. Limits in Leq dB(A) (day / night): Industrial 75/70, Commercial 65/55, Residential 55/45, Silence zone 50/40. 3. So the silence zone limits are 50 dB (day) and 40 dB (night). 4. The answer is (C).
Explanation
A silence zone is the area within 100 m of hospitals, schools, courts and similar places. Its noise limit is the lowest of all zones: 50 dB(A) by day and 40 dB(A) by night. Day time is 6 a.m. to 10 p.m. and night time is 10 p.m. to 6 a.m.
Why the other options are wrong
A: The night limit can never be higher than the day limit, so 50 and 60 is wrong. B: 40 and 30 dB is lower than the notified standard. D: 60 and 50 dB is not the limit for any zone; the silence zone limit is 50/40.
Shortcut
Remember 75/70, 65/55, 55/45, 50/40 for Industrial, Commercial, Residential and Silence zones.
Common mistake
Mixing up the residential (55/45) and silence zone (50/40) limits.
Correct answer: C) 50 and 40, respectively