Should changes occur, then it is checked whether the data can
be described with one of the four models. The basic criterion is
the frequency range where the main change is occurring: in the
low frequency range, i.e. between 1 and 10 Hz, the medium frequency
range, i.e. typically 100–1 kHz, the high frequency range,
i.e. between 10 and 100 kHz, or a constant change over the entire
frequency domain. The other frequency ranges should correspond
to the model as well.