Last night I watched a documentary about the stone age people in the British Isles.
It clamed they had advanced knowledge of acoustics. They tried to prove this by going into the Stone Age barrows and creating a noise. The walls of the barrow were built, they claimed, to resonate at a particular frequency. This frequency was claimed to be ‘infrasound’, below 20 hertz.
The particular frequency in a barrow they visited in Scotland was 2 hertz. When a drum was played as well as the audible noise the 2-hertz infrasound volume was substantially increased because of the layout of the barrow. Of the two scientists the one who wasn’t playing the drum said he felt a strange sensation coming over him. He said it was like his body had gone to sleep but his brain was still awake and he felt extremely relaxed. They put this down to the 2-hertz frequency resonating throughout his body.
Now I thought ‘that’s good’.
For example;
I’m scared to death of dentists. Why not in the waiting room have a speaker that sends out 2-hertz frequencies to relax everyone? There could be loads of potential uses to calm people. Is anyone using such a method?
My first thought: It’s got to be a big barrow. Let’s look a a one-dimensional barrow :). For constructive interference (resonance) you’d want the length to be a multiple of half wavelengths. For air the velocity of sound is about 340m/s, which means that a wavelength at 2Hz is 170m. Things get a bit more complicated if the chamber is round, with a domed roof etc, but in general you’d need a pretty big resonance chamber.
Second thought: He felt calm? Most people feel uneasy and queasy when exposed to high intensity infrasound (Also note that it takes a massive 125dB to perceive 2Hz noise! That’s a lot of energy to come from a drum! (~3W/m[sup]2[/sup] (cite)) This site cites the effects of 2-5Hz infrasound as:
The infrasound wasn’t loud enough for him to hear only to feel it in his body.
As I said it made him feel extremly relaxed.
The barrow was only one example, though it was quite large. Caves in France were also given as examples as well as Stone Henge in England and somewhere in Ireland.
the local spyshop sells Infrasound generators that are quite small and look much like a walkman with a speaker on it. The feller there said it caused nausea and uneasiness. Being an amatuer magician/seance’ performer…I thought that it would be pretty swell to get hold of one, but I was severely skeptical as to whether or not it would work. (and I certainly wasn’t going to drop $60 to find out).
What are the odds that it would work? How well documented are the effects of Infrasound?
Physics requires that something that could put out meaningful amounts of INFRAsonics is going to have to be very large. There is no way that a device the size of a walkman could put much below 20hz, lot alone get down to 5hz with any kind of power.
Before buying one of the Walkman sized infrasound generators, try waving your hand at a pace of two waves a second. You’re generating 2 Hz infrasound if you do that, and you’re generating as much as the Walkman could if its speaker was only able to move as far as your hand is moving. You will notice pretty near as boring an acoustic display as mortals can imagine - other than making a candle flame waver, I bet it is powerless.
If you drive your car pretty close behind a tractor-trailer rig at highway speeds, and have all the windows down, you can often feel a powerful infrasound effect as the vortices shed by the truck wash over your car and alternately pump air to the left and the right through the passenger compartment. Seems to me this is around 2 to 4 Hz. I find it unpleasant - and though the air is moving plenty fast, the pressures aren’t really that big.
thanks for the info and links everyone. I’m heartens me to see my skepticism was valid in that case. I guess more of those physics lessons stuck than I thought. (Even if I wasn’t able to articulate why I didn’t think it would work at the time).
After reading the link provided by Steve Wright I’ll have to add a third thought: Helmholtz resonator!
I can’t explain here and now, but if you follow this linnk you’ll find a very good explanation. (hint: blowing over a bottle generates a wavelength much longer than the length of the bottle!)
It would in fact be possible to create a cave of reasonable size wich would resonate in infra-sound frequency. The power would have to come from something more powerfull than a drum though. How about wind?
They discussed this possiblity on the show - postulating that the ceremonies took place during storms. Quite possible I suppose - storms would seem (to primitave humans) as periods of high spirit activity, or perhaps a time when the “gods” need to be placated…
My previous car was a Toyota Carolla with a sunroof. Once, I was driving with the roof out, but all the windows rolled up. At the right speed (35 - 40 MPh) the interior of the car went “Whump, whump, whump…”, with the whumps coming one or two per second. I always imagined I was exciting the lowest resonance, like blowing on the mouth of a bottle. tc’s one-dimensional barrow calculation suggests otherwise, but I don’t know what else could cause it.
Last night on BBC1 they had a show about ghosts and stuff. A bit of it was about a scientist in Coventry who worked in a lab. The cleaner had previously said she had seen a ghost in the room and he was working on his own at night a couple of days later.
Out of the corner of his eye he though he saw a ghost but when he turned to face it it disappeared.
The next day he said he felt very uncomfortable in the lab and was working on a hacksaw blade that he had in a table vice. Then the blade started to shake. He said he was quite disturbed but thought he had an idea. He checked the sound in the room and a fan on the roof was emitting infrasound with a frequency of 19 hertz. This is what caused the blade to shake and apparently made his eyeballs vibrate so he thought he was seeing something.
A little bit off topic but there was also a section on one of the most haunted places in Scotland. It was in Edinburgh in the vaults under a bridge. The got people to stand in different areas of the vaults on their own and then recorded what happened. Of the areas of the vaults that were said to be haunted all of the subjects said they felt/saw something. A scientist came in and there was also infrasound in these areas as well as something to do with different magnetic forces than the rest of the vaults.
Didn’t this phenomenon turn up in the movie, uh…Phenomenon? Travolta could more keenly detect the ULF (ultra-low frequency) sound waves coming up warning of an earthquake or making people sick or something bad like that? Also, that chick shaved him in that movie.
This has a cool account of a woman, Charlotte King, who supposedly can hear infrasound and has used it to predict numerous earthquakes. (Search for the charlotte king effect on the page.) I also Googled “charlotte king hoax” and didn’t come up with much, so it’s automatically true, right??? Cool story, anyway.