After making the recording, researchers listen to the tape over and over again, listening for any sound that resembles a voice. They may also use a computer to analyze any voices that do emerge. Here is an example of the analytical process used at The Ghost Investigators Society:
Researchers may also use software to make the recorded sound more audible. "I use software to remove background noise, to boost the strength of their voices or to remove clicking or hiss from the recording," explains Dave Oester, Ph.D., cofounder of the International Ghost Hunters Society. "Some EVP require no filtering at all; they are very clear. EVP voices are filled with emotions and are never monotone."
When using a very quiet cassette or reel-to-reel recorder, researchers often run a fan or play radio static or the babble of prerecorded voices (usually in a foreign language) during playback, because they say that the background noise helps the voices form on tape. The theory is that the communicator translates the noise into words.