Electronic voice phenomenon (EVP) are electronically generated noises that resemble speech, but are not the result of intentional voice recordings or renderings. Common sources of EVP include static, stray radio transmissions, and background noise. Some have claimed these sounds are of paranormal origin, while there are natural explanations such as apophenia (finding significance in insignificant phenomena), auditory pareidolia (interpreting random sounds as voices in their own language), equipment artefacts, or simple hoaxes. Recordings of EVP are often created from background sound by increasing the gain (i.e. sensitivity) of the recording equipment.
As the Spiritualism religious movement became prominent in the 1840s–1920s with a distinguishing belief that the spirits of the dead can be contacted by mediums, new technologies of the era including photography were employed by spiritualists in an effort to demonstrate contact with a spirit world. So popular were such ideas that Thomas Edison was asked in an interview with Scientific American to comment on the possibility of using his inventions to communicate with spirits. He replied that if the spirits were only capable of subtle influences, a sensitive recording device would provide a better chance of spirit communication than the table tipping and ouija boards mediums employed at the time. However, there is no indication that Edison ever designed or constructed a device for such a purpose. As sound recording became widespread, mediums explored using this technology to demonstrate communication with the dead as well. Spiritualism declined in the latter part of the 20th century, but attempts to use portable recording devices and modern digital technologies to communicate with spirits continued.
American photographer Attila von Szalay was among the first to try recording what he believed to be voices of the dead as a way to augment his investigations in photographing ghosts. He began his attempts in 1941 using a 78 rpm record, but it wasn't until 1956, after switching to a reel-to-reel tape recorder, that he believed he was successful. Working with Raymond Bayless, von Szalay conducted a number of recording sessions with a custom-made apparatus, consisting of a microphone in an insulated cabinet connected to an external recording device and speaker. Szalay reported finding many sounds on the tape that could not be heard on the speaker at the time of recording, some of which were recorded when there was no one in the cabinet. He believed these sounds to be the voices of discarnate spirits. Among the first recordings believed to be spirit voices were such messages as "This is G!", "Hot dog, Art!", and "Merry Christmas and Happy New Year to you all". Von Szalay and Bayless' work was published by the Journal of the American Society for Psychical Research in 1959. Bayless later went on to co-author the 1979 book, Phone Calls From the Dead.
"Phone calls from the dead" is an alleged paranormal phenomenon in which people receive telephone calls that they claim are from spirits of the deceased. People have reported receiving telephone call from deceased relatives, friends, or even from someone not directly known by the recipient in life. The communication is usually simple and brief, and is usually a one-time occurrence.
In 1980, William O'Neil constructed an electronic audio device called "The Spiricom." O'Neil claimed the device was built to specifications which he received psychically from George Mueller, a scientist who had died six years previously. At a Washington, DC, press conference on April 6, 1982, O'Neil stated that he was able to hold two-way conversations with spirits through the Spiricom device, and provided the design specifications to researchers for free. However, nobody is known to have replicated O'Neil's results using their own Spiricom devices. O'Neil's partner, retired industrialist George Meek, attributed O'Neil's success, and the inability of others to replicate it, to O'Neil's mediumistic abilities forming part of the loop that made the system work. However, there is strong evidence to suggest that the recordings of conversations were falsified by O'Neil, specifically with an electrolarynx. The clearly audible vocal fricatives in the recordings, along with the fact that during the hours of recordings O'Neil's and Mueller's voices never overlap (as would happen in normal conversation), support this theory.
Most explanations of EVP can be categorised as either paranormal, explaining the source of the voice, or non-paranormal. Explanations of the latter kind usually posit (except in the case of hoaxes) that there is actually no 'voice' at all, merely the illusion of a voice due to various effects.
A number of paranormal explanations have been suggested for the origin of EVP. Explanations include living humans imprinting thoughts directly on an electronic medium through psychokinesis and communication by discarnate entities such as spirits, nature energies, beings from other dimensions, or extraterrestrials.
There are a number of simple scientific explanations that can account for why some listeners to the static on audio devices may believe they hear voices, including radio interference and the tendency of the human brain to recognize patterns in random stimuli. Some recordings may be hoaxes created by frauds or pranksters.
Investigation of EVP is the subject of hundreds of regional and national groups and Internet message boards. Paranormal investigator John Zaffis claims, "There's been a boom in ghost hunting ever since the Internet took off." Investigators, equipped with electronic gear—like EMF meters, video cameras, and audio recorders—scour reportedly haunted venues, trying to uncover visual and audio evidence of ghosts. Many use portable recording devices in an attempt to capture EVP.
The steampunk Ghostbusters parody troupe The League of STEAM send up the concept of capturing EVPs: one of their members, ostensibly a disciple of Thomas Edison, carries a backpack with a large phonograph horn on it, which supposedly can capture EVPs and record them onto wax cylinders."By Niscor"