2026/07/23 by Wathela Alhassan, D. Rosinska, M. Suchenek +2
#astro-ph.IM
We investigate the seasonal variability of atmospheric infrasound and its contribution to Newtonian noise (NN) at the Sos Enattos site, a leading candidate location for the Einstein Telescope (ET). Infrasound data recorded at three stations -- SOE0 (surface), SOE1 (-84 m), and SOE3 (-160 m) -- are analyzed over multiple seasons to characterize both temporal variability and the depth dependence of the acoustic field. The amplitude spectral density (ASD) at 1 Hz exhibits a clear seasonal modulation, with winter levels exceeding summer values by 10--15 dB, primarily driven by variations in wind conditions. Using the measured pressure spectra, we estimate the corresponding NN contribution within a standard atmospheric coupling framework. At the surface station (SOE0), the median characteristic strain reaches ∼ 10-22 at 1 Hz, whereas at the deepest underground station (SOE3) it decreases to ∼ 10-27, corresponding to a suppression of approximately five orders of magnitude. Across all stations and environmental conditions, the inferred NN remains well below the ET-D design sensitivity curve in the 1--10 Hz frequency band. These results demonstrate the strong attenuation of infrasound-induced NN with depth and confirm that atmospheric infrasound does not constitute a limiting noise source for underground gravitational-wave detectors at this site.