This paper discusses analyses of a ground-based outdoor microphone system designed to be weather-robust. This system employs an inverted half-inch microphone placed one-quarter inch above a thin plastic convex circular plate and enclosed in a dome windscreen. The current iteration of the “compact outdoor unit for ground-based acoustical recordings,” nicknamed COUGARxt, is an improvement over its predecessor because of its thicker windscreen and its thinner plate made of a harder plastic material. One system characterization is anechoic chamber testing, where a sound source was placed at different elevation and azimuthal angles relative to the COUGARxt system to understand performance differences. Acoustical effects of plate orientation and the thicker windscreen are discussed. Another analysis consists of outdoor measurements in a windy but otherwise quiet environment. The COUGARxt system shows improved wind-noise rejection between 3 and 100 Hz, which could be important for improved detection of infrasound sources, including sonic booms and long-range launch vehicle noise.
This study investigates the noise from three separate Falcon 9 vehicle launches from Vandenberg Air Force Base, as measured within the community of Lompoc, CA. Although one focus of these tests was to test a variety of acoustical and weather instrumentation systems and configurations, the launches also provides an opportunity to study and compare the launch noise measured under potentially different weather conditions. An analysis of the levels and spectra is shown for different time periods. The prevalence of acoustic shocks is examined in the context of environmental conditions and recording locations.
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