Soaker hose versus compact nonporous windscreen: A comparison of performance at infrasonic frequencies

A compact nonporous windscreen described previously [J. Acoust. Soc. Am. 114, No. 4, Pt. 2, 2323 (2003)] was tested in the field against a soaker hose array to compare performance at infrasonic frequencies. The cylindrically shaped compact windscreen, made of closed‐cell polyurethane foam, had dimensions 0.0762 m i.d. ×0.2286 m height ×0.0127 m wall (3×9×0.5 in.). The low acoustic impedance of the foam permits the propagation of infrasound through the walls of the windscreen with a transmission coefficient near unity. The soaker hoses were 15.24‐m (50 ft.) long and coupled to a Chaparral model 5 low‐frequency microphone. The hose plenum was removed and replaced with the compact windscreen for testing. A sonic boom simulator, located at a distance of 400 m (1/4 mile) from the microphone, generated tones at 3, 4, 5, and 6 Hz. Analysis of the signals received by the interior microphone revealed that the tones transmitted through the windscreen, as well as the reduction of background noise due to naturally occurring wind‐generated turbulence, were nearly identical for the two types of windscreen.