>>2655828the earth resonates at a low amplitude of about 3Hz, and other than that the only significant sources of infrasound are geologic activity and industrial (whindmills, power stations, propulsion, machinery). It's usually very easy to identify these sources or rule them out.
HOWEVER one must also be aware of high tension high voltage powerlines which criss-cross rural areas everywhere and the electric fields can sometimes be perceptible, which can be quite disconcerting if you are not aware of any powerlines nearby
