White Noise
Some facts about White Noise for those who are curious
First of all, what is White Noise?
White noise is the name given to an audio signal that contains every frequency in the audio spectrum, with all frequencies having the same average power. Some of the uses for white noise are loudspeaker testing, measuring the sound characteristics of a room, as input to a synthesizer (which filters the white noise to produce the desired sound), and in paranormal investigations (for information about this application of white noise, see the web site of Long Island Paranormal Investigators). White Noise recordings are also used for therapeutic purposes, as explained below.
John Daintith defines white noise as "noise occurring in a channel and regarded as continuous in time and continuous in amplitude, the noise being uniform in energy over equal intervals of frequency. (Note that, by contrast, white light is uniform in energy over equal intervals of wavelength.)" (source: JOHN DAINTITH. "white noise." A Dictionary of Computing. 2004. [from Encyclopedia.com]).
For the scientists among us, authors Graham Upton and Ian Cook, in "A Dictionary of Statistics", report that "A sequence of errors for successive observations that consists of independent random values from a normal distribution with zero mean is termed white noise." (source: www.highbeam.com).
For the mathematicians among us, www.experiencefestival.com presents a mathematical definition: "White Noise is a random signal (or process) with a flat power spectral density. In other words, the signal's power spectral density has equal power in any band, at any centre frequency, having a given bandwidth. An infinite-bandwidth white noise signal is purely a theoretical construct. By having power at all frequencies, the total power of such a signal is infinite. In practice, a signal can be "white" with a flat spectrum over a defined frequency band."
A more (and VERY) technical description can be found in the book "Stochastic processes" by Emanuel Parzen. A preview of the book, including this technical description of white noise, can be found at Google's books.google.com
What does White Noise sound like?
White noise, sometimes called white sound, sounds like a background "static" or hiss.
"Like all complex sounds, white noise is a mixture of many frequencies: high, low and in between. What sets it apart, though, is that all these frequencies are roughly equal in intensity, giving rise to a toneless hiss rather than something recognizable." (source: Why White Noise Can Be Soothing Is A Mystery (Column). Wisconsin State Journal (Madison, WI). December 4, 2008 [from www.encyclopedia.com).
Long Island Paranormal Investigators describes white noise as "the random non-descript static sound produced by various electronic devices. The sound covers and combines all wavelengths and frequencies. In this way it is like the color white which is really a combination of all colors. Hence the name white noise – the combination of all sounds. Examples of common white noise sources are the radio or television static when set to an empty channel, the hum of an electric fan motor and the babbling sound of a fast moving stream or brook."
The Babylon Online Dictionary describes white noise as "a `sh' noise produced by a stimulus containing all audible frequencies of vibration".
This web site also provides a variety of translations of white noise in other languages. Of particular note is white noise in Klingon - "wab chIS"
The therapeutic use of White Noise
Relaxation
Although no one can explain exactly why, many people seem to find the background "static" or hiss of white noise to be relaxing.
Sleep Enhancement
In many instances, people report that they are better able to sleep with white noise playing in the background than in a silent environment.
Sound Masking
Others who find that they are frequently disturbed by loud sounds from outside the room that they are occupying, report that a background of white noise is effective at masking these outside sounds, allowing them to work, relax, or sleep undisturbed.
See the new alternative to conventional "white noise" ...
