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Acoustic Properties Of Unexplained Rapping Sounds

Ulalume

Ulalume

tart of darkness
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Enfield Raps.jpg


Ran across this tonight - I found it quite interesting.

PDF of paper by Barrie G. Colvin
http://www.sgha.net/library/Unexplained_Rapping_Sounds.pdf

From the abstract:
"The wave characteristics of unexplained rapping sounds have been studied and compared with similiar-sounding raps produced using normal tapping methods. Differences in low frequency wave properties between the two classes of raps have been noted. There are indications that the acoustic properties of the two classes of sounds are different and this technique can be used to differentiate between normal and inexplicable rapping sounds witnessed during RSPK activity."

The photo is an example of the differences between the two kinds of raps in the Enfield poltergeist case.
The PDF contains more examples from other cases.
 
Although I'm stuggling to see for certain (because of my screen resolution) there is a huge difference between the two graphically-represented sounds.

If we assume that the time domain and amplitude calibrations on these oscillograms are of equivalent magnitude (and ignore what appears to be a linear amplitude axis on the 'polt' chart, and a quasi-logrithmic scaling on the amplitude of the lower control chart), the most-significant difference between the two sounds is the absence of any sharp, short-duration onset to the sound.

The alleged 'polt' sound starts slowly (accoustic waveform attack onset), and remains at a sustained average sound level for much longer that the control comparisons.

The decay of the sound is of significantly-longer duration, with the overall charcteristic seeming to be like the noise from a thunder rumble or a geological occurance. Although I've not looked at any of the actual PDF report yet, assuming that filtering and equalisation are equal and neutral on both recordings (both during acquisition and storage), there is a reasonable inference that the harmonic content of the upper soundwave contains much more low-frequency content than the lower control 'triple tap' recording.

A skeptical observation is that the 'polt sound' looks almost similar to a replayed slowed-down recording of a single control tap/rap, but with a displaced start. I'm not saying it is....just that they share some characteristics.

When I get the time, I'll read the report later (I have no faith at all in 'Ghosthunter'/Acorah-style pseuoscience pantomimes, hopefully this is more major league)
 
Spirits are so percussive. If the ghosts can make percussive sounds, why not long, sustained drawn out sounds too? Very little ghost literature mentions non-percussive sounds. If I was a ghost I'd be invisibly bowing the edge of lampshades all day, buzzing, and generating tones.
 
Ermintrude -
did you have time to read the paper yet? It's really too complex to summorize, but I gathered that the sound signature was consistent with tension being formed within a material (wood, or whatever) with the audible "rapping" sound occuring when the tension is released, much different than the normal sort of knock when a material is being struck by an object.

The author does say that it should be taken into account that they were working with recordings of varying quality, from alleged poltergeist cases spanning a period of forty years, but - interesting, to my mind - the signature of normal rapping vs unexplained rapping sounds stayed consistent, regardless.

egregor -
Yes, I would do the same. :)
 
That conclusion from the paper was very interesting (a charachteristic difference being displayed by PK rapping, versus real-world experimental control recordings). I only read the first third, but will re-start it again.

However, a note of caution. Unless I misunderstand their method, it is as if they're analysing other experimenters' PK recordings, ones which have been made publically-available. They've only made their own comparitor recordings...using physically-produced 'percussion'. But I wish they could've independantly-recorded PK rapping, especially if that recorded material displayed the same sustain/swell/decay curve of the cited 'spiritual' examples. Or do I misconstrue their findings through my shallow interpretation?
 
Ulalume said:
View attachment 596

Ran across this tonight - I found it quite interesting.

PDF of paper by Barrie G. Colvin
http://www.sgha.net/library/Unexplained_Rapping_Sounds.pdf

From the abstract:
"The wave characteristics of unexplained rapping sounds have been studied and compared with similiar-sounding raps produced using normal tapping methods. Differences in low frequency wave properties between the two classes of raps have been noted. There are indications that the acoustic properties of the two classes of sounds are different and this technique can be used to differentiate between normal and inexplicable rapping sounds witnessed during RSPK activity."

The photo is an example of the differences between the two kinds of raps in the Enfield poltergeist case.
The PDF contains more examples from other cases.
Click to expand...

I seem to recall reading about this on another site a couple of years ago - Although the report I read was greatly condensed & more simplistic. Fascinating stuff.

I recently downloaded some software which produces 'ambient music' using your computer. The music generator works quite well & is oddly relaxing (but kinda dark sounding) for when you want background noise for studying to etc. But some of its acoustic settings mean nothing to me, so I will probably struggle reading the paper you linked to
Ulalume. But thanks for the reminder of this study.
 
Ermintrude said:
That conclusion from the paper was very interesting (a charachteristic difference being displayed by PK rapping, versus real-world experimental control recordings). I only read the first third, but will re-start it again.

However, a note of caution. Unless I misunderstand their method, it is as if they're analysing other experimenters' PK recordings, ones which have been made publically-available. They've only made their own comparitor recordings...using physically-produced 'percussion'. But I wish they could've independantly-recorded PK rapping, especially if that recorded material displayed the same sustain/swell/decay curve of the cited 'spiritual' examples. Or do I misconstrue their findings through my shallow interpretation?
Click to expand...

Yes, I wondered this at the time I read about it a while back - Did they use recordings of which they cannot be sure of their authenticity from a non-controlled environment?

If so it makes the study a little shaky (table-tipping anyone?) to say the least...
 
I'd been meaning to mention (but lost track) that the author of the above paper is a member of the Society for Psychical Research and I know at least some of the recordings were made by other members of the SPR during investigations - though whether the author himself made any of them, or how many, I don't know.
 
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