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Re: [Phys-l] frequency and wavelength of sound in air



I apologize to the list for this bit of obfuscation. When I did my work in school, which was funded by people interested in finding mines (military, boom, kill people), I was never to mention the fact in official talks, and just say that my research was 'of interest in finding mine-like objects'. It was a bit of spin which was ridiculous, and annoyed me to no end. Everyone saw right through it.

Let's just say that one of the uses to which the Postgraduate School is *probably* putting their thumper is to find buried objects, which are often land mines (for a thumper) or ocean mines (for other sources of sound).





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I'm quite certain there is a lot of interest in using these beams for the same thing that the Postgraduate School uses the thumper for.



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From: Bernard Cleyet <bernardcleyet@redshift.com>
To: Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu>
Sent: Sunday, April 5, 2009 2:16:31 AM
Subject: Re: [Phys-l] frequency and wavelength of sound in air

This is a lab at the Naval Postgraduate School in Monterey. The
boxes (no tops) are lined w/ acoustical foam*. Two piezoelectric
transducers are used. Not surprisingly, the labs are heavily
weighted to ocean acoustics. They not only have three large pools in
the basement, but also a rather good home made anechoic chamber and
one lab. room is used as an echoic chamber. They also have a large
sand pile w/ piezo detectors and a thumper. I leave it to youall to
guess its purpose. [hint: the trailer for analysis and thumper
driver reminds me of those used to find oil.]

* can only be used for a few hours before becoming impregnated w/ water.

bc's first job was topping up and running the filtering system
periodically.


p.s. I wonder is there is an acoustical frequency doubling, etc.
analogous to that in optical non-linear crystals?