Ducking
Ducking is an audio effect commonly used in radio and pop music, especially dance music. In ducking, the level of one audio signal is reduced by the presence of another signal. In radio this can typically be achieved by lowering (ducking) the volume of a secondary audio track when the primary track starts, and lifting the volume again when the primary track is finished. A typical use of this effect in a daily radio production routine is for creating a voice-over: a foreign language original sound is dubbed (and ducked) by a professional speaker reading the translation. Ducking becomes active as soon as the translation starts.