Brown Noise – 10 HoursLow frequency rumble is the predominant sound from this noise clip with very little mid or high frequency. It sound best on a playback system capable of faithfully recreating lows. Brown Noise is a random generated noise similar to White or Pink Noise. Brown noise rumbles as though a train is passing by the next valley over or you are riding along in a spaceship in a science fiction movie. Try it to mask other sounds in the environment or as all night sleep audio.