In cities, there are all kinds of vehicles, such as horns, sirens, brakes, exhaust, engines, motors, the looseness of glass, iron plates and parts in carriages, and the take-off and landing and hovering of aircraft, which will make noise, so a wide variety and an amazing number of vehicles are the main noise sources in big cities. In addition, the noise emitted by various machines and mechanical equipment in factories, enterprises and construction sites is stronger than that emitted by vehicles locally. In daily life, the noise of children, the voice of the building next door, the sound of walking and moving things are also boring noises.
We should try our best to avoid noise. By reforming the transportation mode and improving the operation method, the urban noise can be obviously improved. Reasonable urban planning and architectural design can control the noise interference in dense areas. Urban greening also plays a good role in noise reduction. In order to protect the health of workers in strong noise environment, protective devices, such as earplugs, earmuffs or helmets, should be carried when working.
Many countries are vigorously carrying out the research work of noise control. Now it has formed a new discipline called "noise control", also called "noise engineering". In this new discipline, there are many problems directly related to human health that need to be studied and solved.