system
Given the following post, respond as if you're commenting on Reddit:
human
ELIF: Why do some materials, like tinfoil or chip bags, make so much noise when crinkled.
gpt
So some materials, such as cellophane, have a specific force at which they actually and suddenly bend. Any less force than this and they only flex. The difference is basically that on the bend side the thing actually assumes a new shape, while in flexing it will simply return to its old shape when you stop pushing it.

This is, in fact, why cellophane was chosen to be the wrappers for hard candy. It starts out flat. You engulf the candy. You twist the ends... and they _stay_ _twisted_ because they've been bent. When you untwist the candy from the wrapper you are unbending the material.

So each individual "bending event" has a very specific energy. You apply a steadily increasing force until the one of the stress lines gives way and there is a little "crack" noise. You keep bending and there's another crack as another bend takes place.

Done quickly and all at once they come together in a continuous crackle as a series of individual "cracks".

So that thing where your grandma tries to open the candy really slow to minimize the noise doesn't work. Each "crack" has a fixed volume because it's got a fixed energy. Going slow just makes it all take longer.

As a relevant aside, the flat expanse of membrane on each side of each "crack" event acts as a speaker membrane to move more air more efficiently. And some shapes (like a bag) can form a power chamber like in a guitar or drum to make the nose more efficient. This helps the sound cary or focus.

So anyway, if you take the crinkling material and play with it, you can make the individual "crack" events and note how they are all the same volume no matter how fast you bend the individual sounds pretty much all have the same volume.

So if you are opening something loud in a circumstance where noise is unwelcome, like in a movie, just do it all at once without over doing it. You going slow or with less care than usual just makes the disturbance longer in time or "more rumply" because you were bunching up more material.

But below a certain, fairly loud point you can not "quietly" open the bag or unwrap the candy. The material of the wrapper literally can't be more quiet than it is when being bent.