Representative power density spectra for the different outburst stages using the Insight-HXMT LE data (1–10 keV). The solid lines show the best fit with a multiple-Lorentzian function (dotted lines). The MJD, the corresponding outburst stage and the QPO fundamental frequency are shown for each panel. The left, middle, and right panel show the PDS in the LHS, the HIMS, and the SIMS, respectively.