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Author Topic: Can infrasound be transmitted in a specific direction?  (Read 5935 times)

Offline pennyfarthing

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 ???
Can infrasound be transmitted directionally or is it always omni-directional.
If so, are those using the transmitter affected by the infrasound waves effects.

« Last Edit: 03/02/2009 18:54:32 by chris »


 

Offline Pumblechook

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Re: Can infrasound be transmitted in a specific direction?
« Reply #1 on: 26/01/2009 21:38:22 »
Trcicky I would have thought as the wavelength is so long. 
 

Offline yor_on

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Re: Can infrasound be transmitted in a specific direction?
« Reply #2 on: 26/01/2009 21:54:09 »
I found this about infra sound.
http://www.hbci.com/~wenonah/history/gavreau.htm
But it sounds a little to much as Science Fiction to me:)

I'm guessing that you wonder if it exist as some sort of 'secret weapon'?
Maybe one could create something directed but it seems very difficult.
And involving a lot of machinery.

There seems to be wavelenghts that can create feelings of nausea and disorientation in people.
Depending on age and hearing.

But there are no recent 'experiments' that I've found.
So my guess is that 'they?' have given up on that idea.

http://www.badexperiment.com/tag/infrasonic/

And using 'directed' sound through walls doesn't seem to work either.
Not as a active 'weapon', that is.
You can use sound as a passive/'active' sonar though.



 

lyner

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Re: Can infrasound be transmitted in a specific direction?
« Reply #3 on: 27/01/2009 22:50:42 »
The frequencies classed as infrasound  can be anything below about 20Hz. 7Hz is around the peak of alpha brain activity and is thought to be quite 'effective' as a weapon.
7Hz has a wavelength of over 40m which makes directional transmitting devices inherently very big - at least one wavelength of aperture size is needed for significant directivity and several wavelengths are needed for an actual 'beam'.
It is possible, however, to arrange for a good 'null' to be placed in one (narrow) direction so an operator could be protected from the worst of the effects if he's in the appropriate spot.

There is, also, the issue of efficient radiation of sound energy at those frequencies. A simple loudspeaker wouldn't be much good. Large resonant cavities and horns have been used in the past.

It could be a useful device to leave behind when a position is over-run. This could be switched on when the enemy is in residence and upset their victory celebrations, giving you a chance to storm back in and re-take the position whilst the enemy is laying on the ground, squirming.
 

Offline techmind

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Can infrasound be transmitted in a specific direction?
« Reply #4 on: 05/02/2009 00:12:40 »
To make a directional antenna or aerial for either sound or radiowaves you inherently need a device which is at least several wavelengths in size.

The speed of sound in air is 330metres per second, and the wavelength is 330/(frequency in Hertz). So for 10Hz, one wavelength is 33metres, so you'd need a big antenna or speaker.


There might be some tricks you could play with sending two narrow beams of ultrasound (at say 40kHz) -which is easy to direct- at fractionally different frequencies and arranging for them to beat in your target location at a difference frequency of a few Hz. Normally with a linear medium you need mutliplication rather than addition to yeild the low frequency component, but it you did it with a big enough intensity...??? Ouch!
 

lyner

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Can infrasound be transmitted in a specific direction?
« Reply #5 on: 05/02/2009 09:06:07 »
Techmind
I did wonder about mixing, too, to produce infrasound frequencies. It strikes me that the mixing would need to take place where the effect would count. Non linearity in the ear might produce low frequencies but is it actually in the ear that Infra sound has its effect?
 

Offline Pumblechook

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Can infrasound be transmitted in a specific direction?
« Reply #6 on: 05/02/2009 16:23:24 »
Are ears ultimately non-linear?..Hit em hard enough.     Interesting thought.
 

lyner

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Can infrasound be transmitted in a specific direction?
« Reply #7 on: 05/02/2009 16:49:16 »
Mine are, certainly. I can get all sorts of intermoduation peoducts occuring when there are loud noises around. AND they sound as if they're in my head!
No, really chaps, they're in my head, I tell you. . . jibber  jibber.

To lay down a high level of sound, albeit in a limited direction, could be as hard as producing infra sound - you can generate infrasound mechanically - with fans etc. As long as you can build a big enough resonator, you can match it into air.
 

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Can infrasound be transmitted in a specific direction?
« Reply #7 on: 05/02/2009 16:49:16 »

 

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