Abstract: A method and apparatus for block averaging measurement data from dynamic, repeating input signals, for example, frequency modulated signals, take into account the time variability of the measurement sampling. Each block of measurement data is referenced to a synchronizing stimulus, and measurements are averaged both on the time axis and on the modulation axis. On the time axis, the time alignment for each individual measurement is placed at the center of the time interval during which the measurement was made. For each block of data acquired, the measurement blocks are averaged together in both dimensions, time (x-axis) and modulation (y-axis result being computed), using a stimulus synchronizing signal provided by the user as a time reference (time=0). The stimulus synchronizing signal should be a stable reference with respect to the modulation function being measured. For example, if frequency versus time is being measured, the reference should identify a repeating frequency reference.