Electronic Voice Phenomenon

Within ghost hunting and parapsychology, electronic voice phenomena (EVP) are sounds found on electronic recordings that are interpreted as spirit voices that have been either unintentionally recorded or intentionally requested and recorded. Parapsychologist Konstantīns Raudive, who popularized the idea in the 1970s, described EVP as typically brief, usually the length of a word or short phrase.

Enthusiasts consider EVP to be a form of paranormal phenomena often found in recordings with static or other background noise. However, psychologists regard EVP as a form of auditory pareidolia (interpreting random sounds as voices in one's own language) and a pseudoscience promulgated by popular culture. Rational explanations for EVP include apophenia (perceiving patterns in random information), equipment artifacts, and hoaxes.

As the Spiritualist 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.

...
Wikipedia