White Noise is a hiss-like sound noise that is produced by combining sounds of all different frequencies together; all of the imaginable tones that a human can hear combined together. The adjective “white” is used to describe this type of noise because of the way white light works. White light is light that is made up of all of the different colors (frequencies) of light combined together (a prism or a rainbow separates white light back into its component colors). In the same way, white noise is a combination of all of the different frequencies of sound. Because white noise contains all frequencies, it is frequently used to mask other sounds.