rolloff(rolloffFactor) {
    if (typeof rolloffFactor === 'number') {
      this.panner.rolloffFactor = rolloffFactor;
    }
    return this.panner.rolloffFactor;
  }
How quickly the volume is reduced as the source moves away from the listener
@method  rolloff
@for p5.Panner3D
@param  {Number} rolloffFactor
@return {Number} updated value