Should I buy a white-noise audio CD (not the movie!) as a source of background sound?
White noise is a generic term used around the world by EVP experimenters. In actual practice, experimenters try to select sound sources that have more human voice frequencies. Experimenters commonly use something handy like a fan for background sound–anything that creates noise that is relatively steady-state, and that can then be filtered out. There is some evidence that noise with frequent changes, such as the sound of wind in the trees, is more useful. The transients appear to help begin an utterance. Sound generated by a computer, such as is often found in commercial sound CDs, has not proven to be as useful as the “live” noise one might find as natural background sound in a home. The reason we recommend cheap digital voice recorders is that some models produce a lot of internal noise with many transients, making it less necessary to supply noise. In fact, EVP can be recorded without a microphone if the recorder produces enough noise. Most experimental techniques for recording EVP
