PSN-L Email List Message

Subject: Re: BBC news article about infrasound
From: Arie Verveer greensky@............
Date: Sun, 16 Feb 2003 11:14:30 +0800

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
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

I used a setup similar to " " with a front end
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
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
infrasound.  Mainly around 9 minutes as the the signal reflected and refracted in the
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
as the seismic signature passes you. Though the signal to noise / ratio is poor. As a
one could put a weight on the silicon tubing and maybe it could record quakes. I
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.



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:
> pictures of a monitoring site and the detector:
> a miscellaneous link on infrasound:
> All the BBC articles have additonal links to further reading.
> Regards,
> Charles R. Patton
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