---------------------- multipart/mixed attachment David, Two observations; 1) don't sound waves travel easier in cold air? 2) what was the edge of the coin like? Kind of serated? Greg Newell At 04:49 PM 12/18/2002, you wrote: > >Hi folks, > >Haven't posted for ages! > >I was interested in an acoustic phenomenon yesterday. > >I took a small group of my photography students out in my car do do some >landscape work. We went to a scenic area beside the reservoir. A small >side part of the reservoir was frozen, about a quarter inch thick. > >The day was quiet and still, and very cold, and the part we were at, in a >little valley. One of the students rolled a coin across the ice, throwing >it from a distance about six feet from the water's edge and about six feet >above. The coin rolled a considerable distance. All of us were amazed at >the eerie sound which was produced as the coin rolled over the ice. Its >volume and duration were quite startling. It was a cross between a >metallic sound and a weird bird call, and continued at the same volume as >long as the coin rolled on the ice. > >I guess that the ice must have functioned as a kind of soundboard. But >what bemused me was, where did all the energy come from to make that much >noise? The coin - a UK penny, was only thrown (or rolled) from a height of >about six feet. How could it set the ice so effectively in motion? > >I conclude that conditions must have been just right for an absolutely >optimal transfer of kinetic energy into acoustic energy. > >The students were so taken with this that they all started throwing coins >-pennies and two pence pieces(and some round mints)- on to the ice, to >listen. I felt tempted to return later and make a recording. > >Ice would certainly form a very rigid and brittle soundboard, and I guess >if it was not too thick, or too big an area, the whole sheet could be set >in motion by a rolling penny. Would there be air between the ice and the >water? I'm not sure. > >It was a fascinating effect which we all enjoyed. > >Best regards, > >David Boyce. > > > >_______________________________________________ >pianotech list info: https://www.moypiano.com/resources/#archives Greg Newell mailto:gnewell@ameritech.net ---------------------- multipart/mixed attachment--
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