The Dehum enhancement suppresses humming noises in the audio file.    
The following setting options are available:
Graph
Hum Reduction

Displays the four notch filters.

Button
Automatic Hum Detection

Automatically sets the optimum values for all filters.

The following setting options are available in the Dehum Filter Settings area:
Option buttons
Filter

Offers four different notch filters. These can be defined with the sliders. The four notch filters can also be linked with the Link Filters option button. In this case, all slider changes apply to all filters.

Slider
Frequency

Specifies the frequency of the hum that is to be filtered.

Slider
Gain

Specifies the extent to which hum is to be suppressed.

Slider
Width

Specifies whether the range of the notch filter rises and falls steeply or gently.

 
Frequency
The frequency denotes the oscillations per second of an electrical or magnetic field. With audio files this means that the frequency increases with rising pitch. The unit is Hertz (Hz). The highest magnitude of oscillation is called the amplitude.


Dehum