public void CutAudio()
    {
        float volumeBeforeEnding = audio.volume;

        this.ProgressionAnim(3, (progression) =>
        {
            audio.volume = Mathf.Lerp(volumeBeforeEnding, 0, AniMath.Smooth(progression));
        });
    }
 void Start()
 {
     // Lower the audio after some time in the scene.
     this.Timer(lowerDelay, () =>
     {
         this.ProgressionAnim(3, (progression) =>
         {
             audio.volume = Mathf.Lerp(defaultVolume, lowVolume, AniMath.Smooth(progression));
         });
     });
 }