David,

A few year ago I ran an infra-sound detector and found
the air currents caused a great deal of problems.
Basically most of the signal. Only having a limited
space, I opted for a long length of thin wall silicon tube
coiled in a spiral. This tube was purchased from a medical
supplier. It acted a a large diaphragm reducing the air
currents at the detectors input. I managed to detect
the air pressure induced by the movement of a small local
quake (100 km away) that shook the ground under the detector.
A few observed meteors were detected plus some interesting
yearly changes in the background noise (ocean). I do think the
radial arm on porous tubes close to the ground would be
the best way forward assuming you have the space. My
detector operated 10 hz and lower.

On the drawing board is mark three of the detector but
before I attempted this I wrote a program that calculated
the propagation of infra-sound in the earth's atmosphere.
It's a working program but not polished enough for production.

If you are interested I can send you some image plots on wave
propagation. It explains why a local quakes infra-sound may
bounce right over your location and why thunderstorms can
only be heard a certain distance and so on.

Question: can image files be posted to this site ? Its been
a while since I last posted anything.

It would be good to have a network of these sensors. Great
work.

Cheers Arie

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