Ice Sound Board

[Greg Newell]

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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 

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