Raudive developed several different approaches to recording EVP, and he referred to:
- Microphone voices: one simply leaves the tape recorder running, with no one talking; he indicated that one can even disconnect the microphone.
- Radio voices: one records the white noise from a radio that is not tuned to any station.
- Diode voices: one records from what is essentially a crystal set not tuned to a station.
Raudive delineated a number of characteristics of the voices, (as laid out in Breakthrough):
- “The voice entities speak very rapidly, in a mixture of languages, sometimes as many as five or six in one sentence.”
- “They speak in a definite rhythm, which seems forced on them.”
- “The rhythmic mode imposes a shortened, telegram-style phrase or sentence.”
- Probably because of this, “grammatical rules are frequently abandoned and neologisms abound.”
In this work, Remez and colleagues demonstrated a dramatic change in the way in which sine-wave speech sentences are perceived, depending on listener's specific prior knowledge.
Most naive listeners hear this as a set of simultaneous whistles, or science fiction sounds. However, for listeners that have previously heard this "sound" . Now listen to the first again.
Listening to the sine-wave speech sound again produces a very different perception of a fully intelligible spoken sentence. This dramatic change in perception is an example of "perceptual insight" or pop-out. We have argued that this form of pop-out is an example of a top-down perceptual process produced by higher-level knowledge and expectations concerning sounds that can potentially be heard as speech
Here is another example:
The problem is that anyone recording these "voices" (in the case of ghost hunting) is already looking for them. They have a prior bias and are going to over- examine any anomalous sound and claim they hear speech. I believe that in most cases, the real culprit behind hearing voices of the dead in your tape recordings is Paradoilia. Yes, the same reason you see Jesus in your cheetos. After all, how is the spirit of a deceased person able to produce sound without vocal chords? The human brain is a very powerful tool, able to proccess random information into recognizable images and sounds. This is how we developed language and writing. Don't sell yourself short by writing these sounds off as something paranormal.