Scientific evidence of poltergeist knocking?

[Still Waters]

Has science finally established a paranormal effect?

Paranormal rappings associated with apparent poltergeist activity have been described for many hundreds of years. It is only now that an interesting pattern has been discovered within the fine detail of the paranormal rapping sounds.No explanation can be found for this pattern at present.

The current edition of the Journal of the Society for Psychical Research (SPR), a learned publication dating back to 1882, carries an article by scientist Dr Barrie Colvin B.Sc., Ph.D., showing instrumental evidence for an inexplicable and objective banging sound detected in recordings made during alleged poltergeist activity.

Whereas raps and knocking sounds produced by ordinary means exhibit a normal acoustic pattern, those recorded in alleged poltergeist cases show quite a different sound signature.

Read more...

[Paranormalcy]

Awesome. Even though it is on the SPR site, which I respect, at least from it's original establishment for the name, and the research they're continuing to do, of a practical nature, for current real-world events. Very interesting!

[bLu3 de 3n3rgy]

Yeah that certainly is interesting.

[Grape Soda]

pretty darn cool.

[Gwynbleidd]

Wow that is interesting.

[ships-cat]

This effect - where the sound ramps up to maximum volume then decays - is well known to anyone who programs synthesisers; it is produced by a component called an envelope generator. (traditionaly called ADSR, or 'attack, decay, sustain, release'. Put an organ sound through an envelope generator, and you can make it sound like a piano purely by manipulating the way the sound volume changes over the first few hundred milliseconds from hitting a note on the keyboard.

In the natural world, a percussive 'knock' CAN be 'smeared out' to produce this initial "ramping up" effect detected in the experiment. However, I am only aware of this happening at very high frequencies (WAY above human hearing), typically microwave frequencies, and only when the waves are travelling through specific types of conductors, NOT through the air.

Most interesting.

meow purr

[Ginger]

Wow, got to love science!

[SAmbag]

Anyone care to speculate as to what might cause these noises in non-paranormal (or paranormal) terms?

I wonder what methods were used to try and replicate the sound signatures?

The question arises as to how such a sound is generated. There is evidence which points to the sound arising from within the structure of a material rather than from the surface of it, as would be the case with a normally-produced rapping sound. This phenomenon will be examined further in future investigations of poltergeist activity.

Are they able to rule out things like creaking from an old house/tension release within the structure?

It's nice to see a 100% repeatable test thus far, albeit 10 tries is a small sample size, 100% shows promise! Hopefully we'll see more articles and journals on it in the near future.

[Ignus Fatuus]

Therefore my acoustic bang theory I wrote about a few months back was not too far off ...

... hurray for me!!! LOL

Seriously though it is about time. I have been waiting for this science for awhile. I grew tired of looking like the only idiot.

[TinkyBlink]

Wow, very interesting!

[Codehook]

Actually this is nothing surprising if you go by the standard scientific theory that 'paranormal' knocking sounds are not paranormal at all and are, in fact, simply static noise from recording devices with auto-leveling (or from recordings that have been compressed or amplified). This is very well noted on a recent 'Derren Brown Investigates' documentary regarding exactly this type of phenomenon. The type of devices I mention purposely amplify sound input in low-signal environments (to effectively record somebody speaking quietly, for example). Recordings from devices other than these can be amplified in software to reveal sound in quieter regions.

The side-effect of this is that it also amplifies noise, as anyone who has ever studied any kind of signal processing will know (signal-to-noise ratios). The noise is what is then picked up, and static noise is very unlikely to have the same kind of sound envelope as a regular and real 'knock' sound.

It is very easy to tell whether something is signal or noise, but unfortunately this is almost always overlooked by people 'researching' this type of thing. You can quite easily amplify areas of the recording with no significant sound input (nobody talking or moving around etc.) to a level where you can hear the noise, although this will require much more amplification than on the supposed paranormal sounds. There will always be noise, even on the best recording devices in the world, but the amount you have to amplify the signal before you hear that noise is a good indicator of how likely 'paranormal' sound is to be real. In other words, the better the recording device's signal-to-noise ratio, the more unlikely it is that you will hear these types of sounds (as long as the device does not have auto-leveling).

It would be interesting to read this guy's paper on his research to see whether he has taken note of all of these things regarding signal and noise. From the sounds of that article it implies an ignorance towards it. Looks like that guy analysed the sound envelope, thought of how some natural and real world events could generate such a sound, and stopped there. But I wouldn't like to assume, of course.

Source: Studying music production and sound engineering for 5+ years

[SAmbag]

Actually this is nothing surprising if you go by the standard scientific theory that 'paranormal' knocking sounds are not paranormal at all and are, in fact, simply static noise from recording devices with auto-leveling (or from recordings that have been compressed or amplified). This is very well noted on a recent 'Derren Brown Investigates' documentary regarding exactly this type of phenomenon. The type of devices I mention purposely amplify sound input in low-signal environments (to effectively record somebody speaking quietly, for example). Recordings from devices other than these can be amplified in software to reveal sound in quieter regions.

The side-effect of this is that it also amplifies noise, as anyone who has ever studied any kind of signal processing will know (signal-to-noise ratios). The noise is what is then picked up, and static noise is very unlikely to have the same kind of sound envelope as a regular and real 'knock' sound.

It is very easy to tell whether something is signal or noise, but unfortunately this is almost always overlooked by people 'researching' this type of thing. You can quite easily amplify areas of the recording with no significant sound input (nobody talking or moving around etc.) to a level where you can hear the noise, although this will require much more amplification than on the supposed paranormal sounds. There will always be noise, even on the best recording devices in the world, but the amount you have to amplify the signal before you hear that noise is a good indicator of how likely 'paranormal' sound is to be real. In other words, the better the recording device's signal-to-noise ratio, the more unlikely it is that you will hear these types of sounds (as long as the device does not have auto-leveling).

It would be interesting to read this guy's paper on his research to see whether he has taken note of all of these things regarding signal and noise. From the sounds of that article it implies an ignorance towards it. Looks like that guy analysed the sound envelope, thought of how some natural and real world events could generate such a sound, and stopped there. But I wouldn't like to assume, of course.

Source: Studying music production and sound engineering for 5+ years

Good ol' Derren Brown. I wondered about that too after ships-cat mentioned something similar (that I didn't quite follow because I have no understand of the field).

I imagine that if the 'rapping' sounds weren't audible without a recorder this is a very likely answer, but I assumed they were audible rapping sounds.

[pinewengland]

Most people don't know that EMF can cause what sounds like "EVPS", that's not the answer for all possible EVPS, but should be considered! And found Codehook's reply very interesting. And i'm going to find more info on it. thank you.

[GPS]

Anyone care to speculate as to what might cause these noises in non-paranormal (or paranormal) terms?

The sound signatures in the paper, which rise to a peak intensity more slowly than an 'ordinary' knock, can be explained by the fact that the sound is coming through a solid. Poltergesit raps are usually said to emerge from walls, furniture and other objects. When sound goes through a solid object it splits into two modes of transmission - transverse and longitudinal - one of which goes twice as fast as the other. Thus part of the sound is slowed down relative to the other, causing the kind of slower rise in amplitude that you see in the paper. It could happen if, for instance, a hoaxer was knocking on the other side of a wall to where the researchers and their sound recorder were positioned.

[sinewave]

Unfortunately, much of the science (if any) is left out in this description. It would be useful to know how the recordings were made. What kinds of recording gear were used and what controls were implemented to identify and filter out noise. Simply recording something and calling it unexplained does not mean it came from beyond. Further, he uses just one type of acoustic signature as a control which is hardly representative of of all possible sound sources in all conditions. The findings are merely speculative as it is entirely possible to achieve a less abrupt peak by placing acoustically absorbent materials between the sound source and the microphone. To say nothing of the fact that recording equipment itself can introduce "sounds" that were not present when the recording was made.

[sinewave]

Most people don't know that EMF can cause what sounds like "EVPS", that's not the answer for all possible EVPS, but should be considered! And found Codehook's reply very interesting. And i'm going to find more info on it. thank you.

Exactly. EM fields are always around us and can affect some kinds of recording gear. This is likely what ghost busters tend to call EVPs.

[JohnSage]

It's easy to simply state "we have considered all natural causes and nothing fits!" I would be very interested in a comprehensive list of all considered altenitives. Still I find the research fascinating and the potential implications have sent a chill down my spine.

[Belial]

This all sounds great, BUT - just how does science know and understand what a ghostly sound sounds like, just what is there for them to make a comparison and then the massive claim?

[GPS]

In the paper, the time taken to reach peak sound intensity is typically in the region of 0.01 to 0.05s. This corresponds with what you'd expect if part of the sound had been reflected from walls in a typical domestic room. You only get the really fast peak sound intensity if the tape recorder is close to the sound source (wuthin a couple of metres) when reflections are negligible. Thus, there doesn't seem to be anything unusual or inexplicable about the sounds shown in the paper. In addition, the lack of a high frequency component in the sounds is also what you'd expect if the sound source was reasonably remote from the recorder. This is because high frequebcies are absorbed by the intervening air.

Edited September 6, 2010 by GPS