White noise is a signal (or process) with a flat frequency spectrum. In other words, the signal has equal power in any band, at any centre frequency, having a given bandwidth.

An infinite-bandwidth white noise signal is purely a theoretical construct. By having power at all frequencies, the total power of such a signal would be infinite. In practice a signal can be "white" with a flat spectrum over a defined frequency band.

A signal that is "white" in the frequency domain must have certain important statistical properties in time. For example, it must have zero autocorrelation with itself over time, except at zero timeshift. Conversely, if the autocorrelation of a signal has those properties (zero except at zero timeshift), the signal is white.

Being uncorrelated in time does not however restrict the values a signal can take. Any distribution of values is possible (although it must have zero DC component). For example, a binary signal which can only take on the values 1 or 0 will be white if the sequence of zeros and ones is statistically uncorrelated. Noise having a continuous distribution, such as a normal distribution, can of course be white.

It is often incorrectly assumed that Gaussian noise is necessarily white noise. However, neither property implies the other. Thus, the two words "Gaussian" and "white" are often both specified in mathematical models of systems. Gaussian white noise is a good approximation of many real-world situations and generates mathematically tractable models.

Electronic voice phenomena is today one of the most fascinating areas of paranormal research. Human-sounding voices from unknown origin are recorded on such electronic media as tape recorders, digital voice recorders, video recorders and other devices. Strangely, the voices are not heard at the time of the recording; it is only when the recording is played back that the voices are heard.

(Contrary to the premise of the film White Noise, EVPs are very often found without the use of "white noise" – random static from a radio or television – although this method has been used successfully.)

The phenomenon has been experienced and documented virtually since the invention of recording devices. Skeptics reasoned that the voices were caused by stray radio broadcasts or pre-recorded voices on re-used tapes. EVP researchers were quick to dismiss the second reason, affirming that they only used sealed new tapes for their recordings. And then, of course, digital recorders, which require no tapes, made that argument irrelevant – the voices still showed up.

Aside from outright fraud (and to be sure there is some of that taking place here and there), this left the skeptics with the one "reasonable" explanation: the voices were caused by fragments of radio broadcasts. This dismissive explanation makes it clear that these skeptics – who usually tout themselves as being scientifically minded – have never tried to record EVPs and have certainly not researched the phenomenon very well. (Unfortunately, this is very often the case with skeptics and the paranormal.)

If they had researched it, they would have found that the radio broadcast theory is absurd. Why? Because quite often, these voices actually respond to questions posed by researchers, comment on situations in a relevant manner, and occasionally even address the researchers by name. The chances of a stray radio broadcast doing this with just a few choice words are too remote to even consider by any objective person. Also, the voices are clearly not those of loudmouthed DJs or other broadcasters; they are voices of average people, children, adults, seniors, male and female. Some have accents and some are infused with human emotion. There are real personalities behind these voices, wherever they come from.

It is true that the quality of EVP recordings varies widely. Some are of such low quality that we're left to guess what the voice is saying. There are many, however, that are quite clear and are usually categorized as Class A recordings. These EVPs represent the best evidence for a phenomenon yet to be fully understood.

Where do these voices come from? This is the big question. Do they come from our own subconscious? Are they angelic or demonic in nature? Do they cross over from other dimensions of reality? Are they the voices of dead people?

For the purposes of this article, let us consider the last theory, that they are the voices of dead people. This may be the most commonly excepted theory among EVP researchers. And if this is true, what are the implications of these EVPs and the things the voices are saying?
The ghost phenomenon has always raised unsettling questions about what happens to some of us when we die. Are some of us doomed to walk the earth after death, seemingly unaware of our demise, for an unknown length of time? (If time has any meaning where they are.) Why and how do they remain?

Except in very rare cases, ghosts – that is, apparitions – do not communicate with the living. Usually, they appear and vanish. There have been attempts to communicate with the dead through mediums, séances and Ouija boards, of course, but the results of these methods are dubious or, at best, highly controversial.

EVPs, on the other hand, seem to be direct communication from these spirits. Hard evidence. The voices are right there on the recordings. They respond, answer questions, even ask questions of their own. There are hundreds of these voices documented – maybe even thousands.
You can hear a diversity of examples on our web site here. For example, The Atlantic Paranormal Society, there's a child's voice pleading "Don't go" and a woman saying, "Don't hurt me."
A fate worse than death?

There are EVPs reflecting the full range of human personalities and emotions. These people are not only self-aware, but their interaction with researchers indicates that they are aware of the living. They can hear us and see us. Do they know they are dead? Do they know we are alive? Do they know the difference?

These poor souls seem to be stuck in a limbo, and there is a kind of confusion and uncertainty in many of the things they say. What is their world like? It may be beyond our earthly comprehension, and perhaps we should be thankful for that.

If EVPs are voices of the dead, what does that imply for the fate of some of us? We too might get stuck in that limbo, struggling to make contact with strange beings walking around with tape recorders. I'm not one to think negatively about death and its aftermath, but EVPs present grave evidence that life after death might not always be as clear-cut or as pleasant as we hope.

Next time - "Inside Electronic Voice Phenomena"

- Ron (TAPS)

- We would like to thank Stephen Wagner from About.com for the use of his article in the writing of this article.

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