Other forms: white noises
White noise is a low, humming sound that results from many combined frequencies. There are machines that create white noise to help people sleep, and there are also many examples in nature, like the repetitive crashing of ocean waves.
The sound of steady rain falling is a type of white noise, as is the hum of a large crowd of fans in a football stadium. If you use the whir of a fan or an air conditioner to fall asleep or sleep more soundly, that's also white noise. In physics, white noise is a signal created by several frequencies with the same intensity. The term comes from white light, which is created by combining different colors.