Effectiveness of nonporous windscreens for infrasonic measurements

Abstract

This paper deals with nonporous windscreens used for reducing noise in infrasonic measurements. A model of sound transmission using a modal approach is derived. The system is a square plate coupled with a cavity. The model agrees with finite element simulations and measurements performed on two windscreens: a cubic windscreen using a material recommended by Shams, Zuckerwar, and Sealey [J. Acoust. Soc. Am. 118, 1335-1340 (2005)] and an optimized flat windscreen made out of aluminum. Only the latter was found to couple acoustical waves below 10 Hz without any attenuation. Moreover, wind noise reduction measurements show that nonporous windscreens perform similarly as a pipe array by averaging the pressure fluctuations. These results question the assumptions of Shams et al. and Zuckerwar [J. Acoust. Soc. Am. 127, 3327-3334 (2010)] about compact nonporous windscreens design and effectiveness.

Measurement and characterization of infrasound from a tornado producing storm

“…For these and other issues (Hart & McDonald, 2009;Pepyne & Klaiber, 2012) there is active research searching for alternative windscreen options (e.g. close-cell dense foam; Zuckerwar, 2010; 13 Shams et al, 2005;Alberts et al, 2013;Dauchez et al, 2016) with most infrasound researchers moving to the use of porous domes (Talmadge, 2018). These infrasound signals are nonstationary, but for the purpose of analysis such signals can often be viewed as piecewise stationary.…”

A Review of the Possible Perceptual and Physiological Effects of Wind Turbine Noise

“…Accurate measures of the sound pressure levels of LF and IS around WTs is complicated because of the very long wavelengths of sound at such low frequencies, and the high susceptibility of measurement microphones to atmospheric turbulence (i.e., wind noise). Special strategies such as very high performance wind-shields ( Dauchez, Hayot, & Denis, 2016 ; K. Hansen, Zajamsek, & Hansen, 2014 ; Turnbull, Turner, & Walsh, 2012 ; Zajamšek et al., 2016 ) and the use of microphone arrays with sophisticated signal processing ( Walker, 2013 ) are needed. There is a complex relationship between the wind speed and angle of incidence, atmospheric conditions, terrain, distance to the source and the number and distribution of sources, and the measurement of LF and IS (for an excellent review, see Van den Berg, 2006 ).…”

“…Accurate measures of the sound pressure levels of LF and IS around WTs is complicated because of the very long wavelengths of sound at such low frequencies, and the high susceptibility of measurement microphones to atmospheric turbulence (i.e., wind noise). Special strategies such as very high performance wind-shields (Dauchez, Hayot, & Denis, 2016;K. Hansen, Zajamsek, & Hansen, 2014;Turnbull, Turner, & Walsh, 2012;Zajamsˇek et al, 2016) and the use of microphone arrays with sophisticated signal processing (Walker, 2013) are needed.…”

Mitigating wind noise with a spherical microphone array

“…achieved the best performance. Dauchez et al (2016) studied the performance of a windscreen constructed from a squared plate coupled with a nonporous cavity and showed the mechanism of WNR to be the spatial averaging of the pressure fluctuations over the plate. Hedlin and Raspet (2003) measured the WNR of a cylindrical barrier of 2 m height with a diameter of 5.5 m, and compared to that of the rosette filters with diameters of 18 and 70 m in atmosphere.…”