Mitigation of the effect of changes of atmospheric pressure on gravity detectors: preliminary results obtained with microphones at the Sos Enattos mine

Low-frequency changes of atmospheric pressure contribute to the measurement noise of gravity detectors. On one hand, changes of frequency around 0.05 Hz and below cause tilt of the ground and the instrument placed on it. On the other hand, infrasound waves propagating in the atmosphere change the density of air, and hence cause changes in the gravitational field. These result in undesired movements of the test-masses of gravitational-wave (GW) detectors. One strategy to mitigate the effects of changes of atmospheric pressure on gravity detectors is to put them under the ground. In this study, recent results of infrasound measurements performed at the Sos Enattos mine (Lula, Nuoro Province, Sardinia, Italy) are presented. A designated area near the mine is one of the candidate sites for the Einstein Telescope, a proposed third-generation GW detector that is currently in the preparatory phase. Infrasound is monitored at three levels underground, as well as on the surface. The infrasound background noise 111 meters below the surface, and its relationship with other noise sources were investigated, too.