Pareidolia in Practice. Avoiding the Pitfalls of Patterning with EVPs

Sitting in the woods attempting to record spirit voices with a home-made Raudive diode detector got me thinking a lot about pareidolia.

For those who might not know, pareidolia represents how we as humans are hard-wired to find patterns in randomness – things that are familiar, like faces in trees or rock formations.

It turns out that this “patterning” is an evolutionary advantage – helps us quickly identify potential predators hiding in the bushes, and why we can’t just shut it off.

And it’s not just limited to visual stimuli, you can find plenty of audio and tactile examples as well. Hearing spirit voices when listening to electronic voice phenomena (EVP) recordings is a mainstay of paranormal TV shows.

Konstantin Raudive, one of the early pioneers of EVP (he called it instrumental trans-communication) had a set of “guidelines” to help extract the elusive spirits recorded on his hardware. These are all from his book “Breakthrough: An Amazing Experiment in Electronic Communication with the Dead“:

  • 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 to be forced upon them by the means of communication they employ
  • The rhythmic mode of speech imposes a shortened, telegram-style phrase or sentence
  • Presumably arising from these restrictions, grammatical rules are frequently abandoned and neologisms abound
The Viking 1 “Face on Mars” image of the Cydonian mesa. NASA/JPL
Ghost Adventures: Guess that EVP
Konstantin Raudive

In addition, he describes techniques such as varying the speed of the playback, re-recording the output over and over, and setting the mics to the highest possible input levels.

Clearly, all of the shenanigans with the audio processing and interpretation leave a lot of room for finding meaning in anything captured.

Raudive was no doubt an intellectual. He was a student of Carl Jung, a trained psychologist and a writer. I respect the fact that he dedicated his life to the study of EVP. He must of strongly believed something was there or he wouldn’t have dedicated so much time and energy studying the topic over the course of his life.

However, even an intellect can fall victim to what notorious skeptic, Michael Shermer describes as an “error in cognition” when it comes to pareidolia. We are simply hard-wired to find meaningful patterns in meaningless noise. In statistics, this would be considered a Type I error – the false identification of patterns in data. There’s also the problem of confirmation bias – if you’re an EVP proponent, you’re going to expect to hear something.

Some obvious EVP pareidolia pitfalls can be easily avoided. First, avoid the temptation to process the recordings. Analyze the raw data. While researching examples of audio captured with diode detectors, frustratingly I found very few cases that weren’t run through some type of processing filter (such as Audacity’s voice isolation effect). With enough post-processing you can make audio sound like anything you’d like.

Second, take steps to avoid confirmation bias. Have people listen to recordings and ask them what they hear without first sharing what you’ve heard. Get a wide set of opinions. Unfortunately, leading the witness with “I heard this, do you hear it too?” is a staple of most ghost hunting TV programming.

The fundamental question is whether EVP even exists. One empirical study concluded that the evidence presented did not provide a definitive answer and found psychological causes more fitting. For me the jury is out.

What are your thoughts about EVP? Drop me a line and let me know your EVP experiences or opinions.

Experimenting with the Raudive Diode Detector

Raudive Diode Detector

“Walking up a road at night, I have seen a lamp and a lighted window and a cloud make together a most complete and unmistakable face. If anyone in heaven has that face I shall know him again.” 

― G. K. (Gilbert Keith) Chesterton

For all those aspiring paranormal engineers, this is probably one of the more in depth examinations of the Raudive Diode detector that you’ll find on the web.

If you’re not familiar with the device or Raudive himself, you can check out my earlier post here.

I spent some considerable time building and testing different designs of this EVP recording device and wanted to share my results.

Here’s the TL;DR: There are many different schematics on the internet, the components are similar and I don’t think the specifics matter much. This is definitely a “set it and forget it” type of device. Recording through the diode is different than a microphone as no ambient noise is captured. That plus the metal shielding means there’s not much of an opportunity for a stray signal to get through. You’ll need to record for a long time.

Konstantin Raudive with one of his spirit recording devices

I didn’t get particularly startling results when testing any of the devices, but I only recorded a few minutes for each. Perhaps your mileage may vary.

I tested four different designs: three of my own builds using schematics found on the web and one commercial version. The challenge is that there are several different circuits available (Raudive himself had three different designs) and no clear examples of what successful output should sound like.

I used a Sony PX370 voice recorder for the experiments. This is a great little recorder in that you can adjust the mic sensitivity and it has built in USB for file transfers to PC.

The only modifications I made to the recorded audio was amplification. I’ve heard a lot of clips from other sites that have been heavily processed – with obvious effects like noise reduction and voice isolation. If you do enough post-processing you can make audio sound like anything, so I thought it would be be better to just present as is.

Raudive’s Circuits

Let’s start with Raudive. To the right are the three circuits that he describes in his book. Here’s an excerpt that describes the diode detector:

“A short (6-10cm long) arial is used to give a more or less broad-banded signal, which is rectified by a diode and fed directly by cable to the radio or microphone input of the tape-recorder.”

Raudive states that diagram #1 was used in his earliest experiments, success was had with Circuit #3, but Circuit #2 was only a blueprint.

Here’s a short clip of one of Raudive’s recorded sessions. He had four different methods for capturing “spirit voices”, it’s unclear if this one was from his diode detector. I’m including this as a comparison to the output from my home-built devices.

Commercial Device

To the right is the commercial device that I tested. (I pried it open to see the circuit and what components were included.)

Out of respect for the seller I’m not going to post the schematic, but the circuit is probably closest to Raudive’s third design as there’s no inductor present.

Here’s an audio clip below from a recorded session done from this device. Essentially white noise as expected.

Commercial Diode Detector

Device #1

This device below uses a slightly modified schematic from paranormal research site Many designs are similar with a common ground to a metal box as shielding. There’s much debate as to the usefulness of the shielding which effectively acts like a faraday cage. It blocks electromagnetic interference, but some say it’s useful to have some noise with the signal.

The design below calls for a 500uH inductor, but for this particular build I substituted a 470uH shielded inductor and added a 1.6K resistor between the mic and ground connections of the TRRS connector. The resistor is needed for a mobile phone to detect an external mic is connected. All other components are as specified.

Schematic #1
Diode Detector #1

Here’s an audio clip of a recording session done in a field while using this device. Again, not too exciting, just white noise for the length of the clip.

Device #2

For this device below, I used the same circuit but substituted a 500uH unshielded inductor.

Schematic #1
Diode Detector #2

Here’s a clip from a test using this device. As with the others, I tested outside in a field to avoid interference. The results are the same as well, just white noise for the duration of the recording.

Device #3

The next one below uses a schematic similar to a commercial device as depicted here by Tangram Studios.

At this point I realized I was going to be testing several different circuits and improved my build a bit. I found a larger enclosure, a terminal block and added a prototyping board so I could more quickly swap components in and out. There are two inductors in the case, but the actual parts used were the 470uH inductor and 2nF capacitor below.

Dioide Detector #3

Here’s the recording done with this one. You can hear from the clip that the device almost certainly picked up interference my phone, which was interesting considering it was a good 3-4ft away from the device during the recording. Other than that, my results were consistent with the others – a lot of white noise.


Konstantin Raudive’s “Breakthrough” book included a vinyl with some amazing audio captured from his devices.

Some of the interpretations are no doubt examples of pareidolia, but there are sessions where the “voices” captured are amazingly clear.

Dr. Konstantin Raudive

Unfortunately none of the circuits that I’ve built and tested so far have produced anything remotely close to the audio that he demonstrated. My recordings were very short in length, so perhaps longer sessions might be more productive.

I’m going to continue to test different designs, and as I do I’ll continue to update this page with the results. What’s great about this project is that the circuit is really straight forward with very few components so not a crazy time investment to try things out.

At the bottom of this post I’ve listed some resources for a deeper dive on this topic. If you decide to build one of these, drop me a line and let me know your results!

Resources – Konstantin Raudive Diode Circuit Diagram

Stray Technologies – Diode Kit Instructions – Building a Raudive Diode EVP Device – forum

Breakthrough : An Amazing Experiment in Electronic Communication with the Dead – Konstantin Raudive (1971-03-02)

Here’s the excerpt: “This book is the documented result of 6 years’ arduous research into an astounding scientific phenomenon, accidentally discovered in Sweden. In some ways, and for reasons not yet fully understood, voices of dead persons linked by affection or interest with the experimenter appear during playbacks of tape recordings on which no such voices were audible at the time of the original recording.”

This one is a great read but hard to find, if you’re lucky you might be able to grab a used hard cover edition from Thriftbooks or Amazon. The original version came with a vinyl that contained some of the actual recorded transcripts.

Konstantin Raudive is one of the fathers of “electronic voice phenomena” or EVP. He popularized the phrase ITC or “Instrumental Trans-Communication” to describe his method of “communications” with the spirit world. I built one of the diode detector devices that he details in his book. Check out this post for the results of my experiments.

Here’s the wordcloud of the book text:

Yes, that is Hitler in there. Raudive would like us to believe that Hitler spoke to him in Latvian. Also there are accounts of voice sessions that involve other political leaders. Personally, I’m less interested in the voice transcripts than the ideas behind his recording devices.

If you check out the book, leave a comment and let me know what you think.