Correlation properties of wind noise pressure on the ground surface

Abstract

Recent studies of the seismic displacement of the ground use the theory developed by Jiao Yu to predict the pressure spectrum of the wind noise on the ground. The prediction of the displacement due to this pressure employs the ground properties and the spatial correlation properties of the pressure on the ground. The theory is successful at predicting the amplitude of the seismic displacement at the surface but does not predict the correct behavior with depth. These calculations used the low frequency correlation functions measured by Shields [JASA 1(17), 3489–3496 (2005)]. The sensors in Shields’ study were on the ground surface and may have been subject to stagnation pressure contributions in addition to the surface pressure fluctuations. A new measurement of the surface pressure correlation using 12 microphones mounted in two perpendicular arms, flush to the ground surface, has been performed. Since the arms cannot be moved to align with the wind, new analysis methods have been employed to extract the correlation coefficients along and perpendicular to the wind direction. Initial analysis indicates that the correlation coefficients are significantly smaller than those of Shields and the convection velocity is slightly larger than the .7 *U(2.0 m) used by Yu.