Regression plots for low frequency common drive time versus frequency domain techniques. Regression plots for low frequency common drive time versus frequency domain techniques. Three different moving average Hanning windows were used to low pass filter the time series for the time domain method. The time constants for the filters are as follows: (a) τ = 200 ms, (b) τ = 400 ms, (c) τ = 800 ms. All regressions are significant at p < 0.05 and the r2 statistics are (a) 0.56, (b) 0.81 and (c) 0.80. The unitary slop line is indicated in the figures as a dashed line and represents the ideal mathematical relationship.