h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Infrasound can be dangerous stuff.
Why haven't we been hearing something about it being generated along with all that electrickery?
Doesn't it propagate well in earth? What about water?

Traveller in Time studying ultrasound
"Yes.

Well infrasound means below hearding frequencies.

Yes, yes.

There is a constant hum of ultrasound, caused by wind, thunder, earthquakes even passing traffic and walking generates some infrasound. Fortunately it is nearly harmless. The only negative effects on the human body is after prolonged exposure to high levels (just below sensible motion) you feel fatigue. "

Thanks for your reply, TiT.

I'll not argue about the 'mostly harmless' levels in everyday life.

The aspect I'm asking about is related to the size (both physical and generative) of the beasts we're building. It seems to me that they could generate substantial power levels.

If you Google infrasound you can find some less reassuring bits.
I can actually remember there being talk of developing weaponry, the frequency range was around 7Hz. What's that in wavelength compared to the size of these things?

Please tell me there's no need to worry! (and why!).

Tit - I've just noticed.

Traveller in Time bad at maths
"I will give it a try.
First required some data < http://news.bbc.co.uk/2/hi/uk_news/magazine/3811551.stm >
Towers 80 meters, try long blades 40 meters.
Speed of sound: 340 meter / second

340 / 40 == 8.5 /second == 8.5 Hz
Say 8.5 upto 17 Hz, definitely Infrasound.

However this is only for wind striking over the length of the blades. Most, if not all will strike over the width.
Assume width is 1 meter >> 340 Hz normal audible sound.

Promote them to use vane tips, the most of the wind flowing over the length of the blades will be gone and the infra sound with it.

O, and do not forget to make a law against any object that could cause wind to generate frequencies below 20 Hz. So any object with a length of more then 15 meters should be removed. "

Then there's bearing rumble, vibrations within the tower itself, all the overtones, undertones, beat frequencies...

No wonder there are complaints from locals (I wouldn't be surprised to find that some have substance).

Not too many people will go near the things, might as well put 'em to some use - storing nuclear waste so two wrongs make a right?

One point that's been ignored here... Sound is vibration - vibration is _very_ bad for large metal structures stuck out in in remote locations - don't you think the designers of wind turbines would have built in a way of dampening the effects of these vibrations?

Any sound created from the blades and propagated through the air would be negligable in comparison with vibrations being conducted through the turbine and its tower through to the ground - but unless those vibrations had been damped the thing'd probably fall apart after a few years.



However, maybe they shouldn't build them too close to a zoo... Don't elephants use infra-sound to communicate - next thing you know you'll be getting a herd of elephants trying to mate with a wind turbine.

Traveller in Time on his head
"Vibrations are bad for the structure.

That is why I suppose the wind over the blades is the main contributor to any noise. The airflow will fold into waves, not the blade or tower. "

If you don't get the engineering right, vibrations can cause all sorts of problems - http://www.manchestereveningnews.co.uk/news/s/191/191032_new_blow_for_b_of_the_bang.html

Like everything else, it's probably only dangerous at very high levels. Sonic weapons use *very* high (>140dB) levels. If we can tolerate the continents grinding together a wind turbine is probably pretty safe.

Plus, most of the 'risks' of infrasound are urban myths. There is no 'Brown Note'. There is no frequency that will instantly liquefy your flesh (the closest you can get is rupturing a few internal organs, and as Dave says it would need to be at very high levels). Most infrasound causes nothing more than fatigue and non-specific feelings of unease... sometimes there's nausea, but that's generally after constant long-term exposure.

Not that I've been researching infrasound as a means of creating 'bad vibes' at a horror LARP I'd like to run someday...

Thanks, folks, for the kind of answers I'm looking for.

Vibration: Yes, I'm aware of hazards to structures of all kinds and was sure that the designs will cope with it. Cope, that is, by spreading the effects around, avoiding nodes etc (hence my comment on beat freqs).

Damping it out (nearly) altogether, though, is outside my knowledge and I just can't see it.

Elephants aren't the only creatures using infrasound... we've been confounding, eg, whales ever since powered sailing ships ...and that's part of my reason for asking.

- - -

>Most infrasound causes nothing more than fatigue and non-specific feelings of unease... sometimes there's nausea, but that's generally after constant long-term exposure<

Yep (except for your 'nothing more than'). That's another part of my concern - exposure *will* be long term to many people and huge numbers of various wildlife (already is, to some).

So far, no-one's given me any reassurance. Keep trying, please!

Some think standing sound waves could cause your eyeballs to vibrate, and so make you hallucinate things such as ghosts.

Yes indeed. I read of an experiment that sucessfully reproduced the feeling of being haunted, using infrasound. Subjects reported a feeling of unease, that someone was watching them, and they saw fleeting movements out of the corner of their eye

Subjects were in a lab at the time, and all those feelings and visions disapeared as soon as the sound source was switched off I would love to see more experiments of this nature- infrasound could be the explanantion for a great number of supposed hauntings.

Traveller in Time measuring the hill side
"Also a law against odd shaped rock formations ? "

The previous were new to me... this lot is adding to my concerns - not reassuring at all!

TiT, ref "odd shaped rock formations": your angle is-? Concentrated beams in some directions?

what's hyderonating?

from:
http://www.google.com/search?q=hyderonating&start=0&ie=utf-8&oe=utf-8&client=firefox&rls=org.mozilla:en-US:official

Did you mean: hydrating


No standard web pages containing all your search terms were found.

Your search - hyderonating - did not match any documents.

Suggestions:

* Make sure all words are spelled correctly.
* Try different keywords.
* Try more general keywords.

Rod.. if you don't mind me saying, you seem a little.. paranoid

I really wouldn't worry about GM, infrasound and whatever else it is you're worried about in this thread. Context is everything. I would reserve concern for much more likely causes of early death/species extinction. For example;

Being killed in or by a car, pollution, electrocution, global warming, heart attack, stroke, etc, etc, etc. All these things and more, are far, far, *far* more likely to kill you or cause long-term harm to our species than tinkering with some DNA in an onion or not hearing a windmill

Traveller in Time referring to one of the first postings
"I suggested previously that man made structures longer then 15 meter could generate infrasound.

Hydrating, Cybernating, Hybernating, Hydronating, something inbetween. And I deliberitely constructed a non hit now it is only waiting for it to show up somewhere else. "

Arnie, hyderonating was from Tit's tag - I got similar results to you.

Winnoch2: OK. Paranoid it is on both this and GM/cloning.

I'm generally in favour of science, technology and engineering. I just don't like the idea of encouraging 'progress' without some thought. We, as a species have unthinkingly done enormous damage. And, it's not just our species...

I'll be lucky to get 15 years, but my (and your?) descendants may, conceivably, have to cope with rather worse things than we do...oh shut up Rod.

I'll call it a day now.