Gray Noise

Experts describe gray noise as a noise that has more power at the top of the frequency spectrum and at the bottom of the spectrum, with less density in the middle of the spectrum. Scientists point out that this complements the acoustics of the human ear, so that to a listener, it sounds like every frequency is equally loud. Others have described gray noise as sounding like a three-dimensional kind of sound, or a sound that is not flat, but has some depth to it. Some contrast gray noise to other kinds of noise, like white noise, which is widely used for sleeping aids.

Gray noise has also been useful in testing a person's hearing.