Noise and interference (50/60 Hz, anthropogenic noise)

Measurement of the SR is constantly threatened by interference that exceeds the useful signal many times over. The most pronounced source is the electric power grid with a frequency of 50 Hz (in some countries 60 Hz) and its harmonics. General cultural (anthropogenic) noise from electrical equipment, transport and industry also plays a role, as does interference from nearby lightning Tatsis 2024.

The strategy for suppressing interference is multilayered. At the hardware level, notch filters and bandpass filters help (see #37). At the signal-processing level, interference is suppressed by spectral methods and by removing strong transients (see #42). The choice of location itself is, however, crucial.

It is precisely because of anthropogenic noise that permanent SR observatories are placed as far as possible from civilization — in deserts, polar regions and other sparsely populated places, where the level of grid and cultural interference is minimal Tatsis 2024. This significantly improves the signal-to-noise ratio and enables reliable detection of weak modes.