Space-time correlation of acoustic signals in a turbulent atmosphere

Abstract

Scattering by atmospheric turbulence diminishes the correlation, in both space and time, of acoustic signals. This decorrelation subsequently impacts beamforming, averaging, and other techniques for enhancing signal-to-noise ratio. Space-time correlation can be measured directly with a phased microphone array. In this paper, a general theory for the space-time correlation function is presented. The atmospheric turbulence is modeled using the von Karman spatial spectra of temperature and wind velocity fluctuations and locally frozen turbulence (i.e., the Taylor’s frozen turbulence hypothesis with convection velocity fluctuations). The theory developed is employed to calculate and analyze the spatial and temporal correlation of acoustic signals for typical regimes of an unstable atmospheric boundary layer, such as mostly cloudy or sunny conditions with light, moderate, or strong wind. The results obtained are compared with available experimental data.