Frequency power spectrum of temperature fluctuations in free convection

The behavior of power spectra in a Rayleigh-Bénard convection experiment in a helium-gas cell is reported. The high-frequency part of the data for all Rayleigh numbers from 7×${10}^6$ to 4×${10}^{14}$ is fit by a single functional form, obtained by a natural generalization of a multifractal analysis. Low-frequency data cannot be fit in this form.