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Haunted Houses Explained: Infrasound
anagama writes "For anyone who cringes whenever accosted by topics such as psychics, haunted houses, or any sort of new age drivel; for anyone who thinks James Randi is cool or has an active subscription to the Skeptical Inquirer - you're gonna love this story about infrasound. Here's a quote: "British scientists have shown in a controlled experiment that the extreme bass sound known as infrasound produces a range of bizarre effects in people including anxiety, extreme sorrow and chills -- supporting popular suggestions of a link between infrasound and strange sensations. ... Some scientists have suggested that this level of sound may be present at some allegedly haunted sites and so cause people to have odd sensations that they attribute to a ghost -- our findings support these ideas.""
There have been news articles about infrasound and ELF sound experiments since the Cold War began. Both the US and Soviet scientists experimented extensivel y with infrasound as a weapon, and found that it was effective against troops, except for that one annoying minor problem - it affected both sides equally.
. htm
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The BBC story on the subject also attributes religious feelings in churches to the sound produced by the infrasound generated by the largest organ pipes in many churches and cathedrals.
++ Say to Elrond "Hello.".
Elrond says "No.". Elrond gives you some lunch.
...had this in 1964. See The Three Investigators #1: The Secret Of Terror Castle (by Robert Arthur 1964).
----- On the requirements it said: Windows 98 or better - so I installed Linux
I remember reading The Mystery of the Green Ghost (Robert Arthur, part of the Three Investigators Series) back in 4th grade (1980ish). It's originally published back in 1965, and one of the "techniques" used by the perpetrators to scare people off was using extremely low notes on a pipe organ, too low for them to hear as sound.
Putting the sig back into +1, Insightful since 1995!
It was a most effective tool in keeping the invaders away from places where they were not welcome.
Phoenix
Seriously, they don't mention what frequencies were used (can someone extrapolate from the pipe length), but getting transducers to work so low isn't easy and you would need a DC coupled amp. Bass speakers theoretically go down to 20Hz but the performance falls off.
See my journal, I write things there
phenomenon Audio pronunciation of phenomena ( P ) Pronunciation Key (f-nm-nn, -nn)
n. pl. phenomena (-n)
1. An occurrence, circumstance, or fact that is perceptible by the senses.
2. pl. phenomenons
1. An unusual, significant, or unaccountable fact or occurrence; a marvel.
2. A remarkable or outstanding person; a paragon. See Synonyms at wonder.
3. Philosophy. In the philosophy of Kant, an object as it is perceived by the senses, as opposed to a noumenon.
4. Physics. An observable event.
There goes one.
Now we just have the IR cameras to worry about. I'd say that any type of sound manifesting itself through a medium (wall, floor, etc) would indeed raise the temperature of the medium, which would be detectable by an infrared camera. After all, isn't sound just motion, and isn't heat motion?
But what do I know?
In other contexts, phenomena can refer to an "unusual, significant, or unaccountable fact or occurrence". Scientists do not typically use this definition.
Surely the use of "subsonics" to induce feelings of dread and awe was standard sixties SF fare, and was actually applied to good use in the movie "Earthquake," for which movie theatres installed special bass-enhanced sound-reproduction gear called "Sensurround." By all accounts "Sensurround" was very effective in its original form in that particular movie.
I don't have it at hand, but IIRC in Heinlein's 1966 novel, "The Moon is a Harsh Mistress," the central computer, "Adam Selene," uses his control over HVAC systems to generate fear-incuding subsonics at a critical point in the story?
"How to Do Nothing," kids activities, back in print!
I've heard infrasound can cause hallucinations, but the article doesn't mention that...
Randi published a short story (second section on the page) about a scientist and his haunted lab experience involving infra-sound, but it's merely an anecdote, unlike the study.
Robots are everywhere, and they eat old people's medicine for fuel.
I guess all those trains should have killed me by now, since I work right next to tracks. There's regularly low frequency pressure waves at huge amplitudes going through me.
I think you seriously overestimate the potential for damage that this represents. It's mostly just annoying, not fatal. I'd think the pressure levels that are fatal are ones that cause physical damage, like the ones caused by an explosion.
I've had enough abrasive sigs. Kittens are cute and fuzzy.
Um, yes. Did you even bother to READ the story?
Frelling idiots with moderator points.
"Population 1,656"
showing up in 1941 even had some occasional mentions of the use of subsonics to scare off invaders.
And she's even got a rather cute website :)
Or as I have often put it, science is a religion. It attempts to explain our world and justify our actions based on that explanation. It's not pure empirical observation and recording, if it ever was (remember that most of the first true scientists in the Western world were monks)
I think Hippocrates and Aristotle would be quite astounded to hear you calling them monks.
Read some Popper and then get back to us. The limitations of individual studies cannot be generalized to the statement that "science is a religion." Scientific knowledge is about falsifiable statements, things that can be disproven. Religion is about non-falsifiable "knowledge" - things that cannot be proven or disproven, ever, but must be accepted or rejected on their own terms.
http://www.randi.org/jr/10-29-2000.html
There is a really well done french film, "Irreversible" by Gaspard Noe that includes infrasound during one of the more unsettling scenes. I commend Noe for using such a genious technique in this film, since it really expresses the gravity of such a significant scene.
::Bleaked::
If you are even in the mood for a quality film, I highly recommend this film.
You need a DC coupled amplifier, otherwise the series capacitors found on one or both ends of an AC coupled amplifier tends to mess things up. You also need to couple this energy into the air.
..... Germanium was harder to make in N-type flavour, so germanium trannies were mainly PNP. Even when silicon took over from germanium, output stages typically were NPN-NPN. Complementary symmetric output stages - at least ones that work properly and don't give lots of even harmonic distortion - are a much later development} more cheaply than a circuit with one or more transistors ..... but that was a looooong time ago.
..... you need to make sure that the air moving away from the cone as it travels forward, doesn't simply travel around to the back of the speaker. If the cone moves slowly then this is more likely. Ideally you want to place the speaker in a heavy, sealed box. An exponential horn on the front might help too - it's the most efficient pattern for coupling a pressure wave into air. You can also use a tuned port to catch reflected sound from the rear of the cone, invert its phase by 1/2 wavelength, and then when the cone pushes at the front, the tuned port also pushes so you get reinforcement rather than cancellation.
Some stage amps are already DC coupled, others can be modded to DC couple them. Thanks to inherent close thermal matching, DC coupled amps built as ICs really do work. Think TDA2030 and bigger cousins - basically just an op-amp with a slew rate good enough for audio. Valve amps, however, almost invariably rely on transformer coupling somewhere and therefore are AC coupled. Same goes for older tranny amps where a transformer could provide the necessary phase-splitting for driving a push-pull output stage {nb, in those days they were invariably PNP-PNP
My old employer used a modified 1kW stage amp, a signal generator and a box of tricks I built with some op-amps and resistors, to apply weirdy DC+AC / DC+rectified AC waveforms to automotive kit they were testing for operation with a noisy supply. {a vehicle alternator gives out unsmoothed rectified AC; the battery acts like a massive smoothing capacitor but sometimes the lead inductance is too much for this to happen, and what if the battery becomes disconnected after the engine has started?}
As for the problem of getting air to move
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I'm a bass fanatic and infrasound has sort of been a hobby of mine for the past several years. Detecting infrasound (frequencies less than 20 Hz) is easy if you have the right equipment and it can be very fascinating, educational, and fun.
Capturing and monitoring infrasound is easy with a PC, low end sound card, and a cheap microphone. The key is having a low enough sample rate and a spectrum analysis program that is designed for monitoring long term events. I am the author of a Linux signal analysis program called baudline. It has many features that make it ideal for infrasound monitoring. For those of you who are interested in this sort of thing I would recommend checking out the image entitled -session basso on the Screenshots page, also many of Mystery Signals contain some interesting bass phenomena.
For baudline infrasound monitoring, some good starting command line parameters would be:
baudline -memory 50 -samplerate 8000 -decimateby 16 -overlap 50
This will capture about 5 hours of data at a 500 samples/second rate which is good for frequencies up to 250 Hz. Increasing the -memory buffers to 230 MB, the decimation ratio to 64, and the -overlap to 100% will have a Nyquist frequency of 62.5 Hz and capture almost a weeks worth of data!