Crackling noise demonstration
Find a piece of paper. Holding it next to your ear,
crumple it slowly into a ball. What do you hear?
Where does the noise come from? Take your crumpled paper, flatten
it out part-way, and then wiggle it back and forth. Can you make
one spot jump in and out?
When the spot jumps in and out, it makes noise.
Paul Houle studied this noise for a summer project in his second year in
graduate school at Cornell. We started by just crumpling paper by hand in
front of our computer's microphone.
Because he wanted to be able to crumple exactly the same way each time,
and because he wanted other people with smaller fingers to be able to crumple
the paper the same way he did, Paul devised an ingenious instrument for
crumpling, out of two bean cans and some tape.
Here is some of Paul's data. Each spike (big vertical line) is a crackle. Some are
much, much larger than others!
Paul found ways to teach the computer to separate the crackling noise into
separate crackles, and taught it to measure the size of each crackle.
What did we learn?