A sound that should not exist in a certain environment. Generally refers to noisy and harsh sounds. From the perspective of environmental protection, all sounds that interfere with people's normal rest, study and work, and those that interfere with people's listening are noise. Noise is a kind of sound that causes people to be agitated or loud and is harmful to human health. Noise pollution mainly comes from social noise such as traffic, vehicle horn, industrial noise, building construction, concert hall, tweeter, morning market and people talking loudly.

Any sound that interferes with people's normal rest, study and work, as well as the sound that interferes with people's listening. In this sense, there are many sources of noise, such as the noise of cars in the street, the voices in the quiet library, the noise of machines on the construction site, and the loud noise of the neighbor's TV.