White noise is a random signal with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency. White noise draws its name from white light, it is actually a sound frequency or a signal that one hears as a gentle hiss, similar to the sound of a waterfall, radio static or the ocean surf. To use a simple analogy, the color white contains the whole spectrum of colors of light. Similarly, white noise is created by using the entire spectrum of frequencies the human ear can hear.
The effectiveness of white noise for EVP recording is the object of much debate among paranormal investigators. Some paranormal researchers insist it acts like an attractor, immediately drawing in any entities in the area while other researchers claim no significant increase in EVPs or other paranormal activity while using white noise and feel it’s more a distraction than a help.
Using white noise during EVP (Electronic Voice Phenomena) investigations, holds that entities take sounds in the ambient environment and somehow reorganize them into coherent words for us to hear. By providing a white noise background you are providing a base of raw sound for the entity to use to form communication. However, a significant drawback to use this technique the white noise can be hard to filter out later when you analyze your recordings and can thus contaminate an otherwise good EVP recording.
White noise can be made from many sources. As previously mentioned, a radio set to an empty channel, an electric fan or similar motor, the babbling of a stream or a running faucet are all good sources of white noise. Additionally, there are white noise generators available (often sold as sleep aids) and software that will generate a white noise signal from a PC.