Stopping audio

Question

I am loading external swfs, each with unique audio.  As a user selects one of four buttons, the existing swf, both visual and audio) should stop and the selected is to start.  There is a default swf that starts when the flv is initially loaded.  When I start the flv, everything functions correctly.  Then, when I click on a different button, the first swf disappears and goes silent.  Again, this is what should happen.
The problem is after a few second (30-40) and as the second swf is playing, the first one starts back up.  I also noticed that if I double click any of the buttons, I get immediate dual audio.  The AS3 I am using is the following.
Any assistance is greatly appreciated.
import flash.display.*;
import flash.net.*;
import flash.events.*;
import flash.media.SoundMixer;
// track previous and current pages
var curr:MovieClip;
var prev:MovieClip;
// "buttons" are MovieClips, not Button symbols!
// Never use Button Symbols for non-linear navigation systems.
var array:Array = [{button:prog_btn, page:"progression.swf"},
                   {button:elem_btn, page:"elementary.swf"},
                   {button:ms_btn, page:"middleschool.swf"},
                   {button:hs_btn, page:"highschool.swf"}];
// load initial SWF
          var l:Loader = new Loader();
    l.contentLoaderInfo.addEventListener(Event.COMPLETE, swfLoaded);
    //Modify the SWF below to the SWF that is to be played upon starting the WBL
    l.load(new URLRequest("progression.swf"));
// initialize buttons
for each (var obj in array)
    var b:MovieClip = obj.button as MovieClip;
    b.page = obj.page;
    b.addEventListener(MouseEvent.CLICK, onClick);
function onClick(e:MouseEvent):void
    // load the swf file refenced by the button.page property
    var l:Loader = new Loader();
    l.contentLoaderInfo.addEventListener(Event.COMPLETE, swfLoaded);
    l.load(new URLRequest(e.currentTarget.page));
function swfLoaded(e:Event):void
    // assign the loaded swf to the curr variable
    curr = e.target.content as MovieClip;
    curr.y = 100;
    addChild(curr);
          // if prev is valid, remove it
    if (prev)
    //prev.gotoAndStop(1); comment out by smh to eliminate dup audio
          removeChild(prev);
          SoundMixer.stopAll();
    // assign curr to prev, so the process can run again for the next click event
    prev = curr;

Answer 1

Thank you for the feedback.
I modified the section of code where I do the initial .swf load to declare a new variable to the following:
// load initial SWF
var initial:Loader = new Loader();
    initial.contentLoaderInfo.addEventListener(Event.COMPLETE, swfLoaded);
    //Modify the SWF below to the SWF that is to be played upon starting the WBL
    initial.load(new URLRequest("progression.swf"));
I then added the unloadAndStop() line of code in the onClick function to initiate prior to loadiung the next .swf:
function onClick(e:MouseEvent):void
    // load the swf file refenced by the button.page property
    var l:Loader = new Loader();
    initial.unloadAndStop();
    l.contentLoaderInfo.addEventListener(Event.COMPLETE, swfLoaded);
    l.load(new URLRequest(e.currentTarget.page));
I am still having the same issue.
Steve