Regarding Infrasound;  over the last year I had been experimenting with the
detection of infrasound and found the following. The upper zonal winds play
an important roll in detecting infrasound from a distance source. The sound
is refracted as it goes through the atmosphere and the zonal winds can act as
a reflecting layer. (Typically around 50 km ). These zonal winds change direction
and velocity within the year and thus the detection of  infrasound varies. Using the
ocean as a infrasound source you can determine when Zonal winds change direction
( On a season). Also their is Diurnal wind and local wind's. By the way the earth is
a
reflecting layer, so infrasound can bounce between the 50 km region and the earth and

so propagates around the earth. The lower the frequency the further the wave can
propagate.

I used a setup similar to "  http://www.belljar.net/microbar.htm " with a front end
amplifier/filter
and different sensor. You can monitor directly to the atmosphere but wind will, and
I mean "will" be a major problem. On "NO" wind days the results are good, but let
face it the
wind blows more often then it doesn't, especially when the sensor is so sensitive. I
then
tried using a acoustic pip array with some success. But my station is located in a
wooded area
and the array size was limited. So I tended to record wind and its turbulence. In the
end I used
6 meters of very flexible thin walled silicon tube as the sensor head. This was
located in a
building with many vents and dust filters. A pressure bleed was located on the other
side of
the detectors diaphragm. Bingo, it worked well to winds unto 10 - 15 km per hour.

So for most of the time I received a good signal. It detected mine blasts some
160 km away. First you got the seismic signal the after some 7 to 10 minutes you got
the
infrasound.  Mainly around 9 minutes as the the signal reflected and refracted in the
atmosphere.
I ran this configuration for about a 40 days before the seismic and infrasound
station was
closed down.  I do believe you could record infrasound form a local quake if the
winds were
right and the quake intensity was moderate. You do record local infrasound from a
quake
as the seismic signature passes you. Though the signal to noise / ratio is poor. As a
thought,
one could put a weight on the silicon tubing and maybe it could record quakes. I
wonder
what the frequency response would be? Just an idea.

Additionally I have recorded infrasound from meteors and local explosions.

So if anyone is thinking of setting up an infrasound station, let me know and I'll
pass on any info I have.

Cheers

Arie

To stop spam my email is now broken in 2 bits. Join this "greensky" to
"@............"
without the "  ".



> "Charles R. Patton" wrote:

> FYI, some articles about infrasound.
>
> main article on volcanoes and nuclear blast monitoring:
> http://news.bbc.co.uk/2/hi/in_depth/sci_tech/2003/denver_2003/2763657.stm
>
> pictures of a monitoring site and the detector:
> http://news.bbc.co.uk/2/hi/science/nature/1522932.stm
>
> a miscellaneous link on infrasound:
> http://news.bbc.co.uk/2/hi/science/nature/2309505.stm
>
> All the BBC articles have additonal links to further reading.
>
> Regards,
> Charles R. Patton
>
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