A notch filter is a band reject filter with an extremely small bandwidth. It can remove noise at a known single
frequency (e. g. mains hum at 50 or 60 Hz) from a sound recording.
Configuration:
pole radius: a float between 0 and 1, specifies the sharpness of the filter,
the greater the sharper, 0.98 is a good value for the pole radius.
num filters: number (1 to 10) of frequencies that should be removed.
Cut Frequencies: this the array of cut frequencies