Upper bounds on the VHF GWs derived from four observational methods for transient and persistent events. From the top panel to the bottom panel, we show the sensitivity of the four methods SPST, SPMT, MPST, and MPMT. The four typical VHF GW sources are represented by lines of different colors and shapes in the figure; shaded areas of different colors indicate different types of events, while solid, dashed, and dotted lines of different colors indicate the detection sensitivity in different cases.