Comparison of wind filter designs for infrasound sensors

Abstract

Sensors in infrasound arrays measure the total acoustic field that contains signals of interest as well as coherent and incoherent noise. Modern array designs utilize sensors that have a quantified response that extends across the acoustic spectrum from the infrasound passband (<20 Hz) into the low-end audible passband (<1000 Hz). Mechanical wind filters applied to individual sensors are an integral part of array designs that reduce incoherent noise and improve the signal-to-noise ratio of coherent signals. Common forms of these filters are porous hose rosettes and domes, which provide spatial averaging of coherent energy over the dimension of the mechanical filter. These filters also provide additional noise reduction by limiting the sensor’s sensitivity to the effects of the turbulent boundary layer. This presentation will focus on direct comparison of four wind filter designs: 4- and 10-hose porous hose rosettes, a 1-m fabric dome, and a high-frequency shroud. The analysis presented will quantify similarities and differences in the wind filter performance that led to recommendations for specific use cases dependent on expected environmental conditions. [Permission to publish was granted by the Director, Geotechnical and Structures Laboratory.]