Wednesday, 3 April 2013

EVP without the E?

Fan noiseIt was the unmistakable sound of a child calling. I looked around but there was no one there. I checked nearby windows in the street where I was walking. None were open, unsurprising given how cold it was, and there was no one visible in them. Then I heard the sound again. This time I realised its true source. It was a windy day and there was a tree bending in the wind while emitting the strange distinct human-like sound. It was like EVP with the E - a human sound without any electronic recording equipment involved.

OK, there were no actual words involved but I've heard those too, on occasion. I have, several times, heard sounds with recognizable words, only for them to turn out to be unusual environmental noises. One of the most common is electric fans. These give a white-noise like sound and I've heard short 'phrases', or even 'singing', sometimes. The diagram above is a spectrogram of some fan noise.

Given that 'formant noise' can produce apparent words in recordings from non-speech environmental sounds, there seems no obvious reason why it shouldn't also occur 'live', with no recorder involved. The examples I've mentioned appear to support this idea. So the question that naturally arises becomes, why don't we hear the 'voices' when EVP recordings are actually being made?

When I have deliberately tried to create formant noise I usually can't hear anything voice-like at the time of the recording. However, when I play it back, sometimes there is an apparent voice saying something quite distinct. This is even without reducing the audio spectrum envelope, which definitely increases the voice-like quality of the sound. So what's going on?

I think it is simply a question of attention. When I'm making a recording, I'm not really paying much attention to the sound I'm creating by, say, rustling paper. Even if I do listen hard, it can sound a bit like a voice but I never hear words. But when I play the recording back, I listen for the most voice-like bits and then isolate them. I then play these repeatedly and, often, distinct words emerge.

This most likely happens through the verbal transformation effect. If you hear a word (or phrase) repeatedly, it will eventually transform until it appears to be a different, though similar sounding, word. The transformed words have a similar phoneme structure (so 'truce' may transform to ''truth' when heard repeatedly). Research has shown that if you hear a nonsense word (ie. a series of phonemes that are not a real word) repeatedly it is more likely to be transformed to something else than if you start with a real word. Indeed, the most frequently transformed nonsense words are those that comprise phoneme sequences that are never normally heard in a natural language. The word transformations can end up in either real words or nonsense words. Obviously, if you are expecting real words then it is more likely they will end up as real words. So, if you listen to 'formant noise' repeatedly, it is likely to be transformed into real words with the 'missing phonemes' being supplied by phoneme restoration.

Obviously, things like the verbal restoration effect can only work on repeated listenings, which is not possible with 'live' listening. It takes concentrated attention being paid to a particular recording for this kind of effect to occur, which is why I don't hear words when creating formant noise.

So why do I sometimes spontaneously hear 'voices' or 'words' live when listening to certain specific sounds? I suspect it may be a form of audio misperception. When I became sensitive to visual misperception, maybe audio misperception was 'turned on' too. We now know from research that the different senses are more mixed when being processed by the brain than had been previously supposed. Maybe 'switching on' visual misperception also triggers the audio version. I have heard of some other people hearing 'words' in the sounds of electric fans. It is possible that their misperception is 'turned on' too. If any reader has heard such voices, could you please get in touch? I'd also be interested to know if you ever get any visual misperception.
    

1 comment:

  1. Our fridge does that, so much so that I've been convinced someone has a radio on low! It drove me crazy until I figured out what it was.

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