Many may already be familiar with the term, “EVP”, but for those of you who are not, EVP stands for Electronic Voice Phenomenon.
EVP’s are thought to be the sounds of disembodied voices that are captured onto an audio recording device used during an investigation. These voices or sounds are believed to be caused by spirit entities, and most of the time are not heard during the investigation but are only picked up afterwards upon review of the audio data captured.
Investigators use an array of recorders, for example, cassette recorders, modern digital recorders, even their cellphones, preferably enhanced with an external microphone, believing that some entities may be able to communicate through them. A little side-note, if you use your cellphone during any part of the investigation, you HAVE to ensure that it is set to "flight mode" as cell signals and WiFi etc. are prone to affecting other measuring instruments, and you will more than likely have skewed results.
During an investigation, where there is the possibility of an intelligent haunting – meaning that a spirit entity is present and able to communicate – the investigator will ask questions, leaving a gap of 15 – 20 seconds between questions, so that the entity is able to answer. This can continue for varying lengths of time, from a quick 10 minute session, through to hour long sessions. Review of the audio material will take place afterwards, where multiple parties (if possible) would listen for any sounds or voices that may emerge.
Often times these sounds may be soft, other times they are clearly recognizable words or phrases. Software may also be used to filter out background noise or enhance the audio.
One theory of how an EVP is generated during an investigation is that an entity uses energy to manipulate sound so that it is heard as a spoken voice in an audio recording. However, there are also non-paranormal origins of EVP’s, including static, radio wave interference, or simply background noise.
There may be times when sounds that are recorded are distinct words or phrases, and even very clear answers to very specific questions posed by an investigator. One has to watch out for "Audio Pareidolia" and be wary of such at all times.