Acoustic response of rigid pipe wind-noise reducers for infrasound measurement.

Abstract

A network of rigid pipes with multiple inlets is one commonly employed strategy to filter out pressure fluctuations generated by wind when making infrasound measurements. This talk presents a model of the transfer function of such a rosette filter using a computer model (DeltaEC) that includes thermo-viscous effects at the walls of the pipes. Measurements of this transfer function have been made utilizing the coherence between a calibrated reference microphone and a calibrated microphone shielded by the wind-reduction rosette and these data will be compared to the model. Rosettes with pipes of varied lengths were tested and modeled. The response of the rosette as a function of the vertical arrival angle of the incident plane wave will also be presented. [Work supported by US Army Space and Missile Defense Command.]