The pre-processing of ambient noise data refers to the filtering of the raw data before proceeding to further analysis ([[cross-correlation]], [[inversion]]……). Raw seismic data can be collected by either [[geophonesgeophone]]s, [[seismometers]], or from authorized official bodies. There are also public ambinet noise source maps available in recent years<ref name="tonyking4" />. Since the seismometers collect all ambient seismic signals from all directions, the produced seismic waveforms may not reflect the actual background seismic vibrations. Instead, they often contain some occasional seismic signals from earthquakes and other instruments, which is unnecessary in general and thus required to be removed<ref>{{cite journal |last1=da Silva |first1=Cicero Costa |last2=Poveda |first2=Esteban |last3=Dantas |first3=Renato Ramos da Silva |last4=Julia |first4=Jordi |title=Ambient Noise Tomography with Short-Period Stations: Case Study in the Borborema Province |journal=Pure and Applied Geophysics |date=2021-04-22 |volume=178 |pages=1709-1730 |url=https://doi.org/10.1007/s00024-021-02718-x}}</ref>.
