#### Low-pass filter

The low-pass filter used in the algorithm is an adaptive butterworth filter. In the expert panel you can control the following parameters of the filter.

## Roughness

The rougness determines how smooth the filtered spectra is. A high value of the roughness means that the filtered spectrum is smoother. This parameter is optimized in the parameter optimization.

## Frequency cutoff:

The frequency cutoff parameter determines the initial value of the frequency cutoff in the adaptive butterworth filter. It is given in terms of the Nyquist-frequency. The value of this parameter has to be between 0 and 1 and it is optimized during the parameter optimization.
The algorithm can automatically find optimal values for both the frequency cutoff and the roughness parameter.