A Waterfall Plot is a graph displaying a series of frequency spectra versus time. This XYY presentation shows amplitude(Y)versus frequency(X)incremented along a second, sometimes vertically offset Y axis, Time. This plot is used to show a change in vibration frequency characteristics over time.
Another similar presentation is called a Cascade Plot, which shows a series of frequency spectra versus shaft rotative speed. This plot is used to evaluate the change in vibration frequency characteristics during machine transient conditions.
