EVPs are believed to be spirit voices that get recorded in response to questions asked, or simply at random. Paranormal investigators believe that spirits use energy to electrically manipulate sound that can be picked up by digital recorders.
Usually the EVPs are short phrases or a single word that is often difficult to understand due to static or other background noise. It usually clear that a voice was recorded, but in most instances, what the voice is saying is subject to interpretation. When people look for proof of a haunting, EVPs are often cited as evidence.
In 1982, a woman by the name of Sarah Estep founded the American Association of Electronic Voice Phenomena (AA-EVP) now known as the Association TransCommunication (ATransC), The ATransC is a nonprofit organization which serves to increase awareness of EVP.