The Karaoke Filter tool filters frequencies from the audio file that are the same on both channels of a stereo file. On older recordings, this is usually the voice. However, if the voice is not distributed evenly on both channels, you can perform some fine tuning.   
The following sliders are available:    
Vocal Pan

Specifies the channel and intensity with which the voice is to be filtered.

Gain Compensation

Increases the volume of the audio file, which had become quieter because the filter was applied.

The Vocal Frequency Band area specifies the frequency band of the voice. The following sliders are available:
Lower Frequency

Specifies the lower frequency limit for the voice. This is typically a value of 100 Hz.

Upper Frequency

Specifies the upper frequency limit for the voice. This is typically a value of 8000 Hz.

 
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.


Karaoke Filter