Another approach to ducking is through the use of Side-Chaining. Side-chaining consists of monitoring the level of an audio signal and using it to manipulate another audio signal. A concrete example of side-chaining occurs in radio broadcasting where a DJ's voice automatically ducks the music volume.
When using Side-Chaining as part of mixing, you are essentially taking volume information from input signal with the Wwise Meter effect and using it to affect other parts of the mix.
More information about side-chaining: