Science Questions

Why do crisp packets and sweet wrappers make so much noise?

Sun, 14th Sep 2008

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Question

Vince Magno asked:

Why do crisp packets and sweet wrappers make so much noise?

Answer

Dave - Well, I think this is quite a complicated one.  I think one of the things is they’re big sheets so if you move them like this piece of paper any movements they make are very well connected to the air because they’ve got a large area.  If they move a bit then the air has to move.  The vibrations in them get transferred to air very easily.  Also if you take a piece of paper of a crisp packet and crumple it, it doesn’t just fold neatly and you get nice even folds.  You tend to get complicated folds which actually become quite strong.  When you break those you actually release a load of energy which vibrates everything and connects to the air.  The air vibrates well and makes a lot of noise.

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V Magno asked the Naked Scientists: I love your show! I've really learned a lot from it and find it very entertaining. Keep up the great work! Something has been bothering me for years. I occasionally like to sneak a late night snack from the kitchen and while I make every effort to keep the noise down so I don't wake anyone up, I find it impossible to open a bag of chips (you call them crisps, right?) quietly. Why is the typical snack bag so noisy when you're opening it? On a related note, why does an ordinary sheet of paper make so much noise when you crumple it? I suspect it has something to do with its stiffness since soft materials with the same dimensions are nearly silent when handled in a similar manner. And finally, I wonder if there is a market for quiet snack bags? Vince Magno (not mango) New Jersey What do you think? V Magno , Fri, 12th Sep 2008

Of course, there are actual studies on the noise of a candy wrapper! 

http://minerva.simons-rock.edu/~ekramer/Sound/ Evie, Mon, 15th Sep 2008

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