(5) to calculate the Ib-value: Ib = log10 N1 a2 − − log10 a1 N2 , a1 = µ − α1σ, a2 = µ + α2σ, (5) (6) (7) Sensors 2018, 18, 3503 4 of 19 where N1 and N2 represent the lower amplitude limit and upper amplitude limit of each amplitude distribution ...