Hi, This may be of interest, It deals with a Infra sound detector
I constructed a few years ago.  See:

http://www.iinet.net.au/~ajbv/Infra/Infra.html

Chris (  ChrisAtUpw@....... ) on this mailing list made some good
suggestions and improvements. As yet I haven't entered them on the
site. But soon.

A friend asked me this: could it be used to hear earthquakes.?
Now that was a good question. I didn't really have a good answer.

Arie




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