$\frac{1}{f}$ noise near the percolation threshold $X_c$ of carbon-wax mixtures was carefully studied. The noise spectral density was found to diverge with a power-law dependence on $X-X_c$. Our results might be qualitatively explained by carrier-number fluctuations, produced by tunneling conduction, in infinite clusters.

• Received 26 November 1984

DOI:https://doi.org/10.1103/PhysRevLett.54.2529