Notch Filter

input file : source soundfile

output file : destination soundfile (when marked)
or result.wav (for unregistered files)

processing mode : local or global

The notch filter is designed to attenuate a particular frequency component of the signal and has a narrow width so as not to affect the rest of the recording. The filter has two adjustable parameters.

The notch frequency (expressed in hertz) specifies the component due to be removed. The notch frequency must be in the range [20 Hz , 0.45(sampling frequency)]

The 3-dB rejection band (also specified in hertz) decides upon the 'selectiveness' of the filter - the smaller the width of the rejection band, the narrower becomes the frequency 'notch'. The width of the rejection band must be smaller than half of the notch frequency (if not, an appropriate warning is issued).

The notch filter is particularly useful in removing 60 Hz power supply hum.

Linear phase filtering

Previewing results of filtering

Local filtering