JeffH
Senior Member Past Moderator
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Don't stand behind me, I'm about to sling!
Posts: 354
Memphis, TN
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Well, I can get into this post; boy howdy!!!!
Yes, indeed, the rocks sing for the very same reason bullroarers roar. In fact, the sharper the edges on the rock, the louder it will sing.
Musically speaking, a bullroarer is known as a free aerophone. This means that it causes the air to vibrate outside the instrument. The bull roarer does this by spinning fast enough that the air vibrates as it crosses the edge of the blade. When a stone spins fast enough and has a good edge or two, it, too, becomes a free aerophone.
When I was just a boy, I would shoot rocks from my Saunders Folding Falcon slingshot. My grandmother lived on a gravel road so ammunition was plentiful, but rarely round and smooth, even though it was river stone. Over the years of being driven on and having some chert mixed in, the stones tended to have sharp edges.
I would sometimes shoot stones onto the road at about 30 deg. down from horizontal. When the richocheted, the sound was as cool as it gets. Indescribable in text except that it was obviously caused by the spinning stone. Certainly it was doing several thousand revolutions per minute. A really good one would sing for a hundred yards until it went into the woods.
Jeff <><
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