Ocean heave cancellation for a maritime infrasound sensor

Infrasound is very low frequency airborne acoustic energy in the frequency band of 3.3 mHz to 20 Hz, that is inaudible to human beings. Natural sources of infrasound include earthquakes, meteors, volcanoes, tsunamis, auroras, and ocean swells. Among anthropogenic sources are atmospheric and underground nuclear explosions. Because of their low frequency, infrasound waves experience little attenuation, and can therefore propagate to, and be detectable from, very long distances. Land-based infrasound microbarometer sensors and networks have the capability of detecting these signals. In this paper, we investigate the fielding of microbarometer sensors in the maritime environment, on boats, buoys, or unmanned surface vehicles (USV). A particular problem to be overcome is the effect of ocean heave on sensor performance. Ocean heave induces interfering pressure fluctuations on the sensor which may obscure the infrasound signal of interest. In this paper, an ocean-heave cancellation method is developed and applied to infrasound data collected with a sensor deployed onboard a ship at sea. The results show the performance of this approach in cancelling ocean heave-induced interference on infrasound sensors fielded in the maritime environment.