Universal Power Law in the Noise
from a Crumpled Elastic Sheet

Eric M. Kramer and Alexander E. Lobkovsky
The James Franck Institute
The University of Chicago
5640 South Ellis Avenue Chicago, Illinois 60637

Using high-resolution digital recordings, we study the crackling sound emitted from crumpled sheets of mylar as they are strained. These sheets possess many of the qualitative features of traditional disordered systems including frustration and discrete memory. The sound can be resolved into discrete clicks, emitted during rapid changes in the rough conformation of the sheet. Observed click energies range over six orders of magnitude. The measured energy autocorrelation function for the sound is consistent with a stretched exponential $C(t) \sim \exp (-c \, t^{\beta})$ with $\beta \approx .35$. The probability distribution of click energies has a power law regime $p(E)\sim E^{-\alpha}$ where $\alpha \approx 1$. We find the same power law for a variety of sheet sizes and materials, suggesting that this $p(E)$ is universal.