Central Pollution Control Board (CPCB) has set up Real Time National Ambient Noise Monitoring Network in the year 2011 covering nine cities (Delhi, Lucknow, Chennai, Mumbai, Navi Mumbai, Thane, Kolkata, Hyderabad and Bangalore). Under section 2 (a) of Air (Prevention and Control of Pollution) Act, 1981 noise is defined as air pollutant.