Z is the impedance with its real and imaginary part Z r and Z i , respectively. R m is the value of the current-measuring resistor. Parameters α, β and γ are empirically determined based on experimental data. It was suggested that noise can be reproduced well in the mid-to-high frequency range above about 1 Hz, which is the region typically described by ZARC elements . The impedance and its standard deviation are frequency dependent while the other parameters are scalars.