# How does paper make sound when it is torn?

We know that from our experience when we tear up a piece of paper, we can hear a characteristic sound. What is the underlying mechanism behind it? What do the dominant frequencies (edit: I don't mean there is one main frequency of the sound, it is more likely the noise produced contains mostly higher or lower frequencies) and intensity of the sound depend on? The explanation should agree with the real life cases -- here are a few that I observed (correct me if I'm wrong):

1. Dry paper makes louder sound and higher frequencies than wet paper
2. Paper produces louder sound and higher frequencies if we tear it faster
3. It is hard to tell which one produces louder sound, folded paper or single layer paper
4. Folded paper produces lower frequencies than single layer paper

Also, is it the same mechanism that explains the sound produced when we are cutting paper using a scissor?

## 4 Answers

I found a better explanation that seems more convincing to me. I tried sliding two edges of paper perpendicularly, surprisingly the sound produced by doing that is pretty similar with the one produced by tearing paper. It seems that the sound produced is due to the transversal vibration of the whole paper, the friction or the fibers snapping merely acts as driving force. and notice if you hold the paper near the sliding point, the frequency of sound produced becomes higher because the shorter the vibrating paper's length the higher the frequency is(only short wavelengths of standing wave are allowed).

Now which one gives more dominant driving force, friction or snapping fibers?
I think friction is more dominant, because sliding the edges gives a similar sound even without involving any snapping process. Also if we slide it faster, the frequency will be higher.

• Furthermore, wet paper has a higher effective mass density and therefore a different frequency response than dry paper. I wonder if you could fold paper enough times to match the density of wet paper and reproduce the wet-paper sound?
– rob
Commented Mar 29, 2016 at 23:47

If you snapped a piece of wood, it would make a noise, as you tear apart a lot of chemical bonds in the wood, releasing waste energy as sound and a little heat. The structure of paper is fairly similar, except ground up, so it makes a noise as well as you rip apart the same cellulose strands.

• If the paper is wet, it makes less noise when teared. So according to your explanation the bonds must get loosen, but I don't think there is any chemical reaction occurred when the paper gets wet. Because if we dry the paper again, it will be back as nothing happened before. How do you explain this? Commented Jul 7, 2011 at 6:12
• @Paul did You ever see any information/pictures on wood structure? This isn't an answer, this are freewheeling assumptions. Commented Jul 7, 2011 at 9:50
• @Emitabsorb : Yes, no chemical reaction was involved. But, adding water does loosen bonds. When paper gets wet, it "unsets" itself, breaking up the tension that held the fibers together, again causing the uneven texture it initially had. Commented Apr 7, 2016 at 15:43

The fibers snap and the paper acts as a sound board. That is why tearing a larger paper yields more noise.

• That's certainly part of the answer.
– jnm2
Commented Sep 29, 2011 at 20:07

when you tear a paper the fibers on both sides of the paper start vibrating which produce sound. but when the paper is wet the fibers get stuck up to each other and the vibrations are less hence sound is less.