New Scientist magazine, 03 June 2000

   Sweet symphony

   OPENING sweets at the movies [and classical concerts] always creates
   a disturbance.  And now we know why.  The crinkles in commonly used
   wrappings such as Mylar and cellophane are to blame, says a
   Massachusetts physicist.

   "This class of materials seems to be almost uniquely suited for
   producing very loud noises," says Eric Kramer of Simon's Rock College
   of Bard in Great Barrington.

   Kramer studied the sounds that pre-crumpled Mylar makes when it is
   unwrapped and scrunched up again.  He found that the unwrapping
   cacophony is a series of individual clicks, caused by crinkles in
   the material.  They release energy as they go from one stable state
   to another between being crumpled and flat.

   As Mylar crinkles, polymer molecules shift and break.  Some of these
   changes are permanent, creating the crinkles themselves.  But others
   are reversible, storing just enough energy to make a din, Kramer
   believes.

James Kearney
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