Line 29, Column 9 1119: Access of possibly undefined property height through a reference with static type Class.

package  {

  import flash.display.MovieClip;

  import flash.events.Event;

  import flash.media.Microphone;

  import flash.display.StageAlign;

  import flash.display.StageScaleMode;

  public class sound extends MovieClip {

  private var _mic:Microphone;

  private var _sx:Number=0;

  private var sb:Number =_sx;

  public function sound(){

  into();

  }

  private function into():void{

  _mic = Microphone.getMicrophone();

  _mic.setLoopBack(true);

      addEventListener(Event.ENTER_FRAME, onFrame);

  }

  private function onFrame(event:Event): void {

     _sx *=.9;

     _sx +=.4;

  _sx -=_mic.activityLevel * .05;

  big.height +=_sx;

  }

}

}