There's one on the wall here ... http://www.youtube.com/watch?v=-ed3v6Q9H2o&feature=related This isn't what you were thinking of, but might it do? A lot louder than a usual fork. And it's available for sale on Ebay. http://cgi.ebay.com/Resonant-A440-Tuning-Fork-440-HZ-/220649839809?pt=LH_DefaultDomain_0
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