Abstract：Using the observation data of the vertical pendulum tiltmeter in China, we study the influence of different sampling rates on the results of power spectral density. We emphatically analyze the background noise level of the seismic frequency band (200~600 s) of different stations and different types of instruments. The conclusions are as follows: (1) Both single station and national statistics show that the noise levels of the two types of pendulum tiltmeter are equal in the seismic frequency band. (2) There is no obvious regularity in the regional distribution, but due to the influence of ocean and active tectonic movement, the noise levels of some stations in coastal areas are relatively high. (3) The curves of high noise level instrument are generally not smooth and burr-prone. Except for some stations affected by the ocean, they are mostly caused by the observation environment or the instrument itself.
