getLevel(smoothing) {
    if (smoothing) {
      this.amplitude.smooth(smoothing);
    }
    return this.amplitude.getLevel();
  }
Read the Amplitude (volume level) of an AudioIn. The AudioIn
 class contains its own instance of the Amplitude class to help
 make it easy to get a microphone's volume level. Accepts an
 optional smoothing value (0.0 < 1.0). <em>NOTE: AudioIn must
 .start() before using .getLevel().</em><br/>

 @method  getLevel
 @for p5.AudioIn
 @param  {Number} [smoothing] Smoothing is 0.0 by default.
                              Smooths values based on previous values.
 @return {Number}           Volume level (between 0.0 and 1.0)