1/f Fluctuations of Phonon Energy in Water

Brillouin scattering of laser light at the wavelength of 514.5 nm has shown that fractional phonon number fluctuations in water at about 5 GHz have a 1/f spectrum from 10-3 Hz up to the frequency where the spectrum merges into photon shot noise. The power spectrum is inversely proportional to the number of phonon modes N which are involved in the scattering down to the smallest observed value N=7000. The spectrum per phonon mode is equal to 3/f provided the observed 1/N dependence continues down to N=1. Energy partition in phonon modes does not reach equilibrium, at least over the time scale of hours.