Framework for wind noise studies

Abstract

Morgan and Raspet [J. Acoust. Soc. Am. 92, 1180–1183 (1992)] performed simultaneous wind velocity and wind noise measurements and determined that the wind noise spectrum is highly correlated with the wind velocity spectrum. In this paper, two methods are developed for predicting the upper limits of wind noise pressure spectra from fluctuating velocity spectra in the inertial range. Lower limits on wind noise are estimated from two theories of the pressure fluctuations that occur in turbulence when no wind screen or microphone is present. Empirical results for the self-noise of spherical and cylindrical windscreens in substantially nonturbulent flows are also presented. Measurements of the wind velocity spectra and wind noise spectra from a variety of windscreens are described and compared to the theoretical predictions. The wind noise data taken at the height of the anemometer lies between the upper and lower limits and the predicted self-noise is negligible. The theoretical framework allows windscreen reduction to be evaluated in terms of the turbulent inflow properties and establishes practical upper limits on wind noise reduction for varying wind conditions.

A computational study of the effect of windscreen shape and flow resistivity on turbulent wind noise reduction

“…At this high-Reynolds number, a relatively broad spectrum of pressure fluctuations is generated with flow over the upstream circular cylinder, in contrast to a low-Reynolds number flow, where only very tonal pressure fluctuations, related to the von Karman vortex shedding frequency, are generated. The shape of the broadband spectrum of the unscreened case (to be shown shortly) is very similar to those of wind noise in the literature [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] that follow the À5/3-frequency power decay of the spectrum of atmospheric turbulent pressure.…”

“…Since wind noise can be represented nominally by qjUu 0 j, Raspet et al 6 and van den Berg 7 provided more detailed theoretical understanding and mechanisms of atmospheric turbulence effects on wind noise by examining the turbulent velocity correlation and turbulent kinetic energy spectra. However, Raspet et al 6 pointed out that there is another wind noise source due to interaction between the windscreen and the flow. The generated pressure fluctuations around the windscreen produce self-noise.…”

Wind Noise Suppression for Infrasound Sensors

“…For the inertial sub-range, this noise is the dominant source. The pressure power spectral density for the turbulence-turbulence interaction (Pt) is (5) This form of the equation has the modifications made by Raspet et al (8) to extend it into the source region, which is the dominant source of turbulence for infrasound. For low wavenumbers (large scale turbulence), the turbulence-turbulence interaction is a constant.…”

“…For low frequency acoustics, the wind noise contributions due to turbulence have been shown to be divided into turbulence-sensor, turbulence-turbulence, and turbulence-mean shear interactions (6). Recently, these models have been extended to include contributions in the source region of the turbulence spectrum (7)(8)(9). The stagnation pressure is a result of the pressure imparted on an object due to the deflection of the wind around the object.…”

“…Based on work by Raspet et al (8), Yu et al (7,9,10), and Abbott et al (11)(12)(13), a model was developed to determine the pressure at the center of a wind barrier or wind screen. The pressure (Pc) can be calculated by summing the pressure contributions due to atmospheric turbulence from each of the three regions of the wind screen: inside (P1), boundary (P2), and outside (P3).…”