Looking for something scary to do this Halloween season? Try recording the voices of ghosts in your home or in a nearby haunted location. Every ghost hunting show takes a moment to give a definition for Electronic Voice Phenomenon (EVP), one of the more shocking and abundant pieces of evidence paranormal investigators obtain. EVPs are sounds that are caught on audio recorders that could not be heard during their recording. Sometimes these sounds are strange and unidentifiable, but sometimes they are clearly voices. The question is, where are the voices coming from?

EVPs have been a staple in paranormal investigation for the last few decades. One of the earlier references to the phenomenon comes from an interview with Thomas Edison in Scientific American. He was asked about being able to use his devices to contact the dead, and responded that he was not sure about life after death, however...

...it is possible to construct an apparatus which will be so delicate that if there are personalities in another existence or sphere who wish to get in touch with us in this existence or sphere, this apparatus will at least give them a better opportunity to express themselves than the tilting tables and raps and Ouija boards and mediums and the other crude methods now purported to be the only means of communication.

The modern method of obtaining EVP recordings consists of going to an allegedly haunted place, and bringing with you some sort of recording device. Researchers will record for long periods of times while wandering around and sometimes asking questions or talking to the disembodied spirits that may be lingering about. When you have a group of researchers wandering about for a long time, there is usually a lot of audio to then review afterwards. In the popular Ghost Hunters television show, they show the investigators reviewing audio; what you don't see is that they are reviewing hours of material. This is one of the more grueling aspects of paranormal investigation. However, the hard work can pay off when a great EVP is found.