OPENING sweets at the movies 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.
鈥淭his class of materials seems to be almost uniquely suited for producing
very loud noises,鈥� says Eric Kramer of Simon鈥檚 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.
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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.