Eliminating Radio Frequency Contamination for EVP

by Bill Weisensale

The most common explanation for the source of the voices in EVP that is offered by people who have not studied the evidence, is that they are caused by the audio recorder picking up stray radio or television signals. In fact, a number of well-designed experiments have been conducted over the years by very qualified people, to prove that such stray radio frequency signals are not the cause. Reports of two such experiments are provided below.

There is also an experiment shown below that was suggested by one such scientists as a prerequisite to his accepting that EVP are not stray electromagnetic (EM) signals. We believe that nested metal containers, such as the variety found in hobby stores, separated one from another by foam rubber or Styrofoam, would satisfy the requirement while helping to rule out stray sounds.

From the AA-EVP Archive

Here is longtime researcher Bill Weisensale’s response to concerns expressed by Dr Karlis Osis, with the American Society for Psychical Research, about eliminating mundane causes for EVP. From Bill Weisensale’s article in the May 1981 Spirit Voices:

In early 1975 … the controversy was still raging as to whether EVP voices arrived via acoustical or electromagnetic means. (It is generally accepted now that neither is the case.) At the time this was most perplexing. It seemed reasonable to believe that if EVP arrived by electromagnetic signal, a radio receiver would be required in all cases, and yet some methods did not involve any form of radio receiver. Conversely, if they were of an acoustic nature, then all methods would, of necessity, require the use of a microphone, and yet there were some methods that do not involve a microphone.

I reasoned either the voices had to be both acoustic and electromagnetic, depending upon the method of recording, which seemed very unlikely, or they had to arrive by some other kind of energy, which was of neither electromagnetic nor acoustic in nature. (We have come to call this PK energy, for lack of a better explanation.) In order to find out which was the case, I used a (steel) 50 gallon drum with a removable lid …

I brought the drum into the house, laid it on its side on a wooden pallet, and blocked the sides to prevent it from rolling. Next, very small holes were drilled in the drum and lid. A piece of heavy wire, with a solder terminal, was then bolted to the drum and run out through a window where another solder terminal and bolt were used to attach the wire to a steel stake driven into the ground. A second wire and solder terminal was attached to the lid and soldered to the first wire. All connections, drum to wire, lid to wire, wire to wire, and stake to wire, were checked with an ohmmeter to ensure there was no resistance and everything was properly grounded. Before doing the experiments, water was poured around the steel stake to ensure proper grounding.
spirit_voices_1In the initial experiment, which was to check the efficiency of the shield, a battery powered radio receiver was tuned to a strong station, the volume set rather high, and placed inside the drum. A battery powered tape recorder was then connected via patch cord to the radio, also placed inside the drum and the lid bolted into place for several minutes.

Upon removing the recorder and reviewing the tape, it was found that the station was quite clear with the lid off, but when the lid was bolted into place, the station totally disappeared and its presence could no longer be discerned even with the closest listening. We then adjusted the radio to between station static, listening carefully to be sure there were no distant stations present, placed the radio in the drum with the recorder and made several recordings with the lid bolted in place each time.

We found the voices appeared inside of the shield just as they did with no shielding. Also, since the radio and recorder were connected via patch cord and there was therefore no microphone involved, this experiment eliminated (to at least my own satisfaction) both the acoustic and the electromagnetic hypotheses.

[Editor: The May 1981 Spirit Voices and other newsletters are being added to the AA-EVP online document archive as time allows. We are currently up to Spring 1987 with the AA-EVP newsletters. Remember that access to the Archive is a benefit of membership. We highly recommend that you take advantage of this growing library of historical EVP and ITC documents.]

A Suggested Experiment

Initially published in the Fall 2004 AA-EVP NewsJournal

ccaaevp2008-shielded_suggested_by_charles_tartParapsychologist, Professor Charles Tart, was interviewed by The Psychic Times (apparently defunct), a new British publication that is already proving itself antagonistic to EVP. In the article, Tart was quoted to argue that EVP is stray radio, and that we who study in this field have not demonstrated the necessary research discipline to produce the kind of credible evidence that he can take to other scientists.

The diagram is of a shielded recording compartment, EVP from which would answer Tart’s objections. It provides more shielding than a metal can or microwave, but it is not as readily available. We would like to talk to someone who might be able to make one, or who might have one. If possible, we would like to send one to a number of different experimenters in serial fashion, so that many examples can be collected in the compartment. Please let us know if you can help.

MacRae has a Second Article in the JSPR

Initially published in the Winter 2006 AA-EVP NewsJournal
©Alexander MacRae – All Rights Reserved

The October 2005 issue of the Journal of the Society for Psychical Research included a second article by Alexander MacRae. In this one, Alec details the EVP experiments he conducted in the Institute of Noetic Sciences screen room. Remember that the JSPR is a refereed, peer-review journal and that the article necessarily meets the SPR’s high standard for thoroughness and documentation. Here is the abstract:

Report of an Electronic Voice Phenomenon Experiment
inside a Double-Screened Room

By Alexander MacRae


An Electronic Voice Phenomenon (EVP) experiment is described which took place in a laboratory screened against e.m. radiation and also acoustically isolated. The subsequent treatment of the results through sound-processing is outlined, and the final analysis of the results through the use of a unique multiple-choice system is described. Comparative spectrograms of one EVP utterance and the same thing spoken in normal speech are provided to assess the physical basis of the results. The conclusion is drawn that voices of no natural origin were received in the screened laboratory.

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