EVP or to give it its full title, Electronic Voice Phenomenon. This is where a sound is recorded using an electronic device, VCR, Cassette or Digital Tape Recorder that should not be there and that to the listener sounds like a human  voice.

To believers in the paranormal these sounds are thought to be sounds made by the voices of Spirits or Ghosts. To sceptics the voices are due to Taxi radios, local radio stations, mobile phones etc breaking through or perhaps voices from outside that have been picked up by the microphone, but that were not noticed by the investigator at the time. These are all valid possible explanations, all of  which must not be ignored as a first port of call.
 
Some of the sounds that are recorded as EVP's can fall outside the normal hearing range, but are well within a range that can be picked up by even a cheap microphone and recorded on a portable tape or digital recorder.

Sometimes EVP sounds can be heard easily while on other occasions they need to be digitally manipulated using computer sound manipulation software, like Acustica for example. This software should only be used to make the sound clearer, it can however do a lot more.

This is where the problems start this kind of software can also stretch time or alter the frequency of the EVP. If you alter the volume or remove the noise, that's acceptable, if you alter anything else it needs to clearly stated. The original recording should also be made available for comparison. To not do this could be construed as falsification, will not constitute evidence and will be at the mercy of sceptics, trust me I am one.

Most sound recorders can easily record sounds up to 30 KHz, some as high as 40 KHz. A young adults ears would be able to resolve sounds up to 18 KHz, while older people may have problems much above 10 KHz. Human speech by the way is normally in the range 10 Hz to 3.8Khz, which is the range used by telephones.

Some of the sounds that have been recorded that I have come across are pretty convincing, if what is apparently said may sometimes be a little weird.

What usually happens is that it sounds odd and unrecognisable until some one says that sounds like X, after which everyone else that is present who hears the sound also hears X. I have tried this out on a number of different groups of people and it has worked every single time.

In fact if you play the same sound back more than once without telling the group that is what you are doing, you can get them to agree that it sounds like something entirely different using this trick. This seems to indicate that at least some of the time a kind of auto suggestion is going on.  Indeed matrixing isn't just done with the eyes!

The sceptics opinion of this would be that a number of sounds can sound like they have come from humans if you mess around with them enough. Some of you may remember the Dog that used to appear on the BBC That's Life TV program, who would growl, the pets owner moving his jaw to make the Dog appear to say Sausages among other things. While this is not an example applicable to EVP's it is a very good example that a sound that is not human can be made to sound human.

CaSPIR make a point of doing an EVP session at each vigil, using a small Olympus Digital Sound Recorder. Try to have a standard set of questions available so that you know exactly what has been said. When you start say the place and time on the recording along with any obvious noises you can hear (this will help later on) and then get everyone present to say their name. The reason for the latter is that you have a copy of everyone's voice if there are any doubts later. Give it a try, CaSPIR has been very successful recording EVP's, a small selection of these where we have not been able to explain away the voice, can be found on our evidence pages.

By the way no one has yet proven a link between EVP and the Paranormal, now there's a challenge handed out if ever there was.

EVP's are one of a number of phenomena that are sometimes described as being Poltergeistal Phenomena.
 

See also our EVP Workshop Article for more information

Acustica is available online from http://www.acoustica.com/ and is highly recommended