Analysis of the time wave form is often critical to the identification of certain classes of problems. Analysis of the spectrum is common, whereas looking at the time based plots, which was common practice in the past, has at times not been emphasized as a technique for the identification of problems. Spectrum analysis works well, but viewing and studying time waves adds another dimension to the analysis process. The identification of rubs, looseness, beats, modulation and in particular impacts can be improved significantly by viewing time based data. Looking for the presence of multiple impacts when performing resonance testing, the presence of leakage or visualization of what the application of widows does to the data absolutely requires the analyst to look at the data in the time domain. The determination of damping through the use of the log decrement calculation provides a method of accurately computing the damping ratio. In addition, viewing the decay of the response of a resonance allows the analyst to get a true feel for what damping actually represents.