Electronic Voice Phenomena (EVP) are audio recordings offered as proof that ghosts/spirits exist and can communicate with us. EVP are found on recordings of white noise or background noise that seemingly contain human sounding voices that were not heard at the time or recording.
The ghost hunter will press ‘Record’ and then ask a series of questions while leaving pauses in which it is hoped he ghost will answer the question. They may also leave a recording device recording in an empty room.
EVP is not a scientific investigation technique, strange noises and voices captured on recording devices in this manner have lots of potential sources and there is no evidence to support the claim that any voices or noises captured are spirits of deceased people.
EVP recordings made on devices which contain RLC circuitry can be caused by radio signals from broadcast sources. This includes interference from CB Radio transmissions, walkie talkies, and wireless baby monitors. Anomalies generated through cross modulation from other electronic devices can also cause EVP – it is even possible for circuits to resonate without any internal power source by means of radio reception.
It is also common for other external factors to be mistaken as recordings of ghosts. Hands holding the recording device, people in other rooms, passing traffic, draughts, music and vibrations all need to be considered.
When listening to sounds recorded against ambient noise or white noise it can be easy to interpret random noises as familiar noises such as human speech, singing, crying and so on, when in fact they are just random noises of no significance.
Apophenia is defined as “the spontaneous finding of connections or meaning in things which are random and unconnected or meaningless” and is similar to the pareidolia theory above.
The Auto-Gain Circuit
Most hand-held video and audio recording devices have an auto-gain circuit that is designed to to keep a consistent level of sound, basically when a noise is too loud it ‘turns down’ the recording volume and when the environment is quieter it turns the recording volume up in order to try to record something. The obvious problem here is that the sound you are listening to may sound as though it was up close to the recording device but could actually be quite a distance away and it has simply been amplified by the device to keep a consistent level.
Recording devices that have moving parts, such as those that use tapes, can often record what sounds like anomalous sound or EVP when in fact what you are listening to are the clunks, squeaks and ticking sounds of the internal mechanisms of the actual recorder moving.
EVP recordings are often classified by ghost hunters according to their clarity. The classification works as follows:
Class A: Voices are very clear and easily understandable by many.
Class B: Voices are fairly loud and clear and are sometimes audible without headphones.
Class C: Voices are very soft and often indecipherable and often need to be enhanced for clarity.
Although it is true that some recordings are easier to understand this does not support the claim that they are caused by spirits of deceased people.