Some people are convinced that the dead can make recordings of their voices. This is called electronic voice phenomenon-and is usually done by setting up a tape recorder, and putting it in record mode, with the microphone gain turned up high. When the tape isplayed back, these people claim to hear faint voices of people, just who isn’t clear. has this ever been scientifically analyzed? What is the consensus?
Partly, it’s the natural pattern-recognition software in the human brain perceiving voices in the noise that aren’t there. Coupled with the fact that, sometimes, electronics can rectify radio signals under the right conditions, and you have the full extent of EVP.
Cassette recorders are susceptible to radio frequency noise just by the nature of their design. The first thing they teach you in EE school is how easy it is to make a radio receiver. All you need is a piece of wire for the antenna and something that conducts better in one direction than the other. Soldiers in WWII used to make radio receivers out of junk in their backpacks (google “foxhole radio” if you are curious.
Pretty much every electronic circuit in existence these days has all of the elements of a radio receiver in it. The traces on the circuit board act as the antenna, and semiconductors usually have some component that conducts better in one direction than the other. Much of an electronic circuit designer’s time is spent trying to prevent their circuit from ending up as an unintentional radio receiver. Anything with an amplifier in it makes the task even more difficult, since a small amount of electrical noise picked up will amplify into a large and often noticeable signal. Computer speakers are notorious for picking up “chirps” from nearby cell phones, for example.
A cassette recorder has several amplifiers in it. One important one is on the microphone itself. Another important one for this discussion is the circuit which writes the signal to the tape. Both of these amplifiers are susceptible to received noise.
Hand-held digital recorders, which are also popular among the EVP folks, have exactly the same problem. They still have amplifiers in their circuits. They don’t have the write amplifier for the tape head, but they still have the mic amplifier.
So, either a digital recorder or an old fashioned cassette recorder can pick up radio frequency noise and convert it into some sort of audio signal. You could pick up CB radios, cell phones, police radios, far off music radio stations, etc. Since the circuit isn’t intentionally tuning the desired signal (like a real radio receiver would) the signal you get is probably going to be very distorted and noisy.
Note that there’s a trade off between electrical noise immunity and cost. Generally speaking, the cheaper something is, the more likely it will be to pick up noise. Note that EVPs tend to come from cheap hand-held cassette recorders and digital recorders, not high quality studio equipment with noise filters in it.
Add into all of this the fact that the human brain is the best pattern matcher in the entire world. When you pick up an apple, your brain instantly recognizes it as an apple and you have immediately available all sorts of apple-ish data (what it tastes like, the texture of the apple skin, etc). There’s no super-computer in the world that can pattern match the way the human brain can. One quirk of your brain though is the fact that if you give it nonsense, it will try to match something close to the nonsense. So, if you give it a random blob, it will try to form some sort of image out of it (ink blot tests, the face on mars, etc). Give it a random electrical signal, and it will try to make some sort of sense out of it. Some EVP’s that can’t be traced back to human origin are just a result of natural random noise that sounds close enough to something for your brain to interpret it as a voice.
EVP is to audio as JPG artifacts are to pictures. And it’s not far from backwards masking, where you play a song in reverse and listen for words that you didn’t hear forwards.
Did you know there are “researchers” who claim to find “anomalies” in images of the Moon and Mars that they say is evidence of alien disturbance? All they are looking at is the distortion introduced by a lossy compression scheme. The more distortion, the more they find. What they claim to see exists only in their imagination.
Same with EVP. If you magnify random noise enough and maybe process it to bring out certain frequencies, you can find “amazing” anomalies in recordings that appear blank at normal, and unprocessed levels. They then try to interpret random sounds as voices or messages from the spirit world. The EVPers are hearing what they want to hear. Or, as the Paul Simon quote says in the above link,
Of course these voices exist. They are of Nigerian bank officials offering to make you rich. :eek:
The only people who can’t hear the voices are sceptical scientists, who don’t want to hear the truth. 
To my knowledge, EVP has never been subjected to any rigorous scientific inquiry. There are those who claim to have captured EVP in “controlled” conditions (such that would, presumably, eliminate RF interference), but you’ll be hard-pressed to find any evidence of that beyond the anecdotal.
There are several characteristics of the phenomenon in general that give one plenty of reasons to be suspicious:
– They can only be heard via playback
– EVP are invariably short phrases, utterances, or words with little or no meaning; you don’t ever hear nice soliloquies in Middle English about life during the time of Chaucer.
– They seem to inhabit some nether-frequency that typically requires lots of processing to tease out and clarify, which means everything engineer_comp_geek says applies even moreso.
– There’s one now much-sought-after handheld digital recorder that has a very high success rate for capturing EVPs, which always seemed to me rather difficult to explain away if EVP is in fact real.
Even if you’re inclined to keep an open mind to paranormal phenomena in general, on the whole, as EVP has gained more popularity, one would have hoped for more interesting results, and they simply haven’t materialized, if you’ll pardon the pun. Certainly nothing that can’t be explained away by the various alternate theories proposed.