How to remove audio in the background

i am trying to remove my sound from background…

for some reason keep getting this error

Error: Error #2029: This URLStream object does not have a stream opened.
at flash.media::Sound/close()
at Soundbox/killAudio()
at Buttons/onClick()

i hope this doesnt become too much so bear with me please…
this is my document class…

Quote:
package
{
import flash.display.MovieClip;
import Buttons;

public class Dominara extends MovieClip
{
public var s:Soundbox = new Soundbox(); //this calls onto your sound class which loads the sorrow music
public function Dominara()
{
var btnClass:Buttons = new Buttons(exit_btn,credits_btn,options_btn,continue_ btn,newgame_btn);
s.playMain();
}
}
}
now this is my sound class where i call upon to load the music…

Quote:
package
{
import flash.media.Sound;
import flash.media.SoundLoaderContext;
import flash.net.URLRequest;

public class Soundbox extends Sound
{
private var playsound:Sound = new Sound();
private var loadmusic:URLRequest = new URLRequest(“sorrow.mp3”);
private var context:SoundLoaderContext = new SoundLoaderContext(8000, true);

public function Soundbox()
{
trace(“working”);
}

public function playMain()
{
playsound.load(loadmusic, context);
playsound.play(0,20); //this will repeat the soundtrack x amount of times
}

public function killAudio()
{
playsound.close();
}
}
}
as can see i added or thought it would help the killaudio function …

now finally i want to be able to press this button and in it as its pressed it closes or removes the audio…
Quote:
public function onClick(event:MouseEvent):void
{
ruut.gotoAndStop(4);
ruut.s.killAudio();
}
what should i place in my function to close the audio or kill it…