Fast-flush test. Amplitude ratio (AR): A2 (3 mm)/A1 (7 mm) = 0.43. The corresponding damping coefficient is 0.28 . P identifies the period (peak-to-peak distance) necessary for the natural frequency calculation: paper speed/P. In the example, 25 (mm/sec)/2 mm = 12.5 Hz; these data can be then plotted into the diagram showed in Figure 3. N: normal QRS complex.