A comparison of wind filters for deployable remote infrasound monitoring*

Infrasound, or sound at frequencies below 20 Hz, has been observed to be produced by a wide variety of natural and artificial sources, including tornado-producing storms, earthquakes, and nuclear detonations. Because of its low frequency, infrasonic waves undergo little atmospheric attenuation and can therefore potentially be detected several hundreds of kilometers away. As such, monitoring infrasound has a wide scientific application, but the detection of infrasound is highly dependent on the ability to filter wind noise from measured signals. Typically, pipe rosettes and porous hoses are deployed in an array to reduce wind noise, but these aforementioned methods require a large area of land on which to deploy and have a propensity to alter received signals via attenuation or resonances within the filter. Several other methods have been proposed, which include porous domes and fences. However, very few quantifiable comparisons of these methods using controlled inputs exist in public literature. With a view to the remote monitoring of tornado and severe storm infrasound, this presentation compares a sample of wind filters on the basis of their attenuation of a signal and their wind noise suppression, alongside practical considerations for deployment.