what is noise

Noise is an unwanted sound that is considered unpleasant, loud, or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arises when the brain receives and perceives a sound. Noise pollution is defined as any disturbing or unwanted sound that interferes with or harms human health or wildlife. The loudness of sound is measured in decibels (dB), and repeated exposure to sounds of 85 dB or higher can harm a persons hearing. Noise can be continuous, variable, intermittent, or impulsive depending on how it changes over time. Noise can be produced by many sources, including mans vocal cord, a running engine, a vibrating loudspeaker diaphragm, an operating machine tool, and so on. Noise pollution can come from various sources, such as aircraft, railways, road traffic, industrial and manufacturing processes, and domestic appliances.