subject: What is white noise? [print this page] If you are trying to understand "what is white noise?", then you might have come to realize that it's not so easy to get a straightforward answer! Most definitions of white noise are rather difficult to make sense of. Here's just one example:
"White noise is a noise produced by a stimulus containing all of the audible frequencies of vibration."
OK. Technically speaking that's a correct definition. But what on earth does it actually mean?
To really explain what white noise is, I must first explain a little more about what "frequencies" are. In the simplest terms, frequencies are just different "pitches". If I was to play you the middle C note on a piano, the dominant pitch that you would hear has a frequency of 440 Hertz. Lower notes on the piano have lower frequencies (the lowest being just 27.5 Hertz), whereas higher notes have higher frequencies (the highest frequency being around 4186 Hertz).
The human ear is capable of hearing frequencies from as deep as 20 hertz, right up to frequencies as high as 20,000 hertz - way beyond the reach of our piano keyboard!
Now that we know more about what frequencies are, I can explain the concept of white noise a little better. In essence, it is the sound that is made when every single frequency, from 20 Hertz to 20,000 Hertz is playing together at the same time. All the frequencies blend into one another so that it is impossible to hear any particular pitch in the sound. In this sense, it is a "pitch-less sound".
So what does white noise sound like? Here's one example. Do you remember the last time your TV was not tuned into a channel properly and all you could see was a grey swirling screen full of static? If you had turned up the volume on your TV in that moment, what you would have heard would probably have been white noise.
There are plenty of other sounds in our environment that are very similar to pure white noise. The sound of the ocean is a great example of a naturally occurring white noise. The sound of the wind and the sound of rainfall also fall into this category. Even though these sounds may not cover the entire frequency spectrum from 20 Hertz to 20,000 Hertz, we still refer to this genre of pitch-less sound as "white noise".
White noise recordings have some very practical real world applications. For example, these recordings are wonderful for masking other background noises, and so many people use them for sleep, for meditation, or to drown out distracting sounds so that they can concentrate on a specific task. White noise CD and white noise mp3 recordings are also used for relaxation, tinnitus relief, to cure insomnia, and even to prevent eavesdroppers from listening in on private conversations!
