Time Synchronous Averaging
Time synchronous averaging, also called time domain averaging, is a completely different type of averaging, where the waveform itself is averaged in a buffer before the FFT is calculated. In order to do time domain averaging, a reference trigger pulse must be input to the analyzer to tell it when to start sampling the signal. This trigger is typically synchronized with an element of the machine that is of interest.
The average gradually accumulates those portions of the signal that are synchronized with the trigger, and other parts of the signal, such as noise, are effectively averaged out. This is the only type of averaging which actually does reduce noise.
More information on applications of time synchronous can be found in the next chapter on Machine Vibration Monitoring.
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