White Noise

White noise is a signal named by analogy to white light, with equal energy per cycle (hertz). This produces a flat frequency spectrum in linear space. In other words, the signal has equal power in any band of a given bandwidth. By having power at all frequencies, the total power of such a signal would be infinite. In practice, a signal is considered "white" if it has a flat spectrum over a defined frequency band. Interestingly enough, this sound may help you fall asleep.