1. The increasing number of vehicles on the roads are a big source of noise pollution. Increasing traffic jams in congested areas lead to the repeated hooting of horns by impatient drivers causing noise pollution.
2. Noise from construction sites is generally far worse than noise originating from factories. This is because whatever construction takes place noise emissions levels are higher as well as the equipment is inherently noisy.
3. Noise pollution caused by airplanes has been increasing steadily during recent years, especially in the areas close to international airports. This problem has mainly arisen because of the widespread use of heavy long-range jet aircraft. Noise made by jet planes is more disturbing than that of the old propeller driven aircraft because it is of far higher pitch. Jet noise is caused by the violent mixing of the jet of gases from the engine with the surrounding air. It is at maximum level during take-off when the engine delivers maximum thrust, and falls away rapidly as the aircraft climbs. During landing, the main source of high-frequency noise is the sound made by the air compressor and turbine blades. Aircraft pass close to the ground for quite a distance during the landing operation and this noise often constitutes a more sustained environmental nuisance than the intense noise of shorter duration produced during take-off.
