How to record EVP
The point of EVP (electronic voice phenomena) is to capture anomalous voices on audio recordings. It has become popular in recent years to take sound recorders on ghost vigils in the hope of catching such sounds (assumed by some to be 'spirit voices'). Unfortunately, the techniques some people are using to catch these paranormal sounds are unlikely to exclude natural explanations for any unusual recordings.
So what can be done to eliminate natural causes for EVP? It goes without saying that you should find a really quiet place to do your recordings. You could leave a recorder in an empty room but that means you won't know if there were any natural sounds to hear.
- use good digital recorders, rather than analogue, to reduce mechanical sounds
- select a high quality record mode (5000 Hz frequency response or higher)
- some microphones increase their sensitivity when it is quiet (making background noise intrusive) - set the sensitivity to a fixed level if possible
- leave the recorder on a stable surface - movements or knocks to the recorder can be easily picked up by microphones
- it is possible to get electromagnetic interference from nearby electrical equipment (particularly mobile phones) - keep away from such equipment
Even if you observe these precautions, there are still lots of natural sounds to consider. All buildings have their own characteristic noises. You might not notice these at the time of the recording. Also, some voices could be completely natural but just forgotten by the time you analyse the recording. There is an EVP gallery illustrating some of the points made here.
It is possible for electronic equipment to act as a radio receiver. Sound recorders are particularly susceptible to this because the microphone circuit is highly amplified and the radio signal can be rectified by the audio amplifier. Thus, some voices you hear could be fragments of radio transmissions. This kind of interference may particularly affect recorders with external microphones. Microphone leads are also particularly susceptible to interference from electrical equipment. Try using a shielded lead for your microphone or maybe use the internal microphone, if there is one.
Some people look for EVP in white noise. They may use radios not tuned to a particular station, for instance. The idea is that the agents of EVP (whatever they are) can manipulate noise to produce meaningful messages.
White noise is defined as all audio frequencies being present in equal measure. It sounds like a really annoying hiss, though some people find it relaxing. However, such white noise does not exist in nature or even in radios. There are some sounds that approximate to white noise, such as surf crashing on a beach, a waterfall, heavy rain, the wind (in certain circumstances). Artificial white noise-like sources can include air conditioning, fans, noisy plumbing, vacuum cleaners and, of course, detuned radios! However, none of these are really white noise (see pics top left).
Most of these audio sources are formed from lots of tiny sounds occuring randomly at the same time - think of the drops of water in the surf or rain. The detuned radio is picking fragments of distant radio stations too faint to hear plus electronic noise.
The important point to note is that such random (more accurately, chaotic) noise sources will, by chance, sometimes produce sounds that might approximate to fragments of human speech. Their frequency spectrum be similar to that of a real voice, despite being a random event. Human brains are particularly attuned, genetically and by experience, to pick up human voices, even if they are not real. See analysing recordings for more (including pics!).
Patterns in sound
How do you know that a particular sound is speech? It is a question that is central to recording EVP. The human brain can detect speech in noisy conditions and when spoken with a wide variety of accents (unlike most speech recognition software). This flexibility comes with a price - people sometimes detect 'speech' when it is not really present. Scientific research has demonstrated this vulnerability in such things as the phoneme replacement effect and verbal transformation. This is all explained in the section on analysing paranormal recordings which also tells you why you shouldn't use audio editing software on your precious recordings!