Coalescence-induced 1/f2noise

We consider droplets on a substrate that grow according to a power law. When the droplets touch, they coalesce with mass conservation. It is shown by both numerical study and analytical arguments that such a system exhibits a 1/${\mathit{f}}^2$ noise even at low frequencies in the fluctuations of the substrate coverage. This type of noise is expected to be independent of the growth exponent and of the dimensionalities of the droplet and of the substrate.