CODE:

package 
{
	import flash.display.Bitmap;
	import flash.display.Loader;
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.media.Sound;
	import flash.net.URLRequest;
	
	/**
	 * ...
	 * @author DefaultUser (Tools -> Custom Arguments...)
	 */
	public class Main extends Sprite 
	{
		public var graphic:Bitmap = new Bitmap();
		public var music:MySound = new MySound();
		
		public function comp(event:Event):void
		{
			//全読み込みが完了した後の処理
			
			addChild(graphic);	//画像を表示
			music.loop();		//音声をループ再生(今回はすぐに停止するのでループの意味はない)
			music.stop(5000);	//フェードアウトしながら5秒後に音声の再生を停止する
		}
		
		public function Main():void 
		{
			if (stage) init();
			else addEventListener(Event.ADDED_TO_STAGE, init);
		}
		
		private function init(e:Event = null):void 
		{
			removeEventListener(Event.ADDED_TO_STAGE, init);
			// entry point
			
			var ml:MyLoader = new MyLoader();		//MyLoaderをインスタンス化
			ml.fLoadGraph("damy.png", graphic);		//画像の読み込みをリクエスト
			ml.fLoadSound("minutes.mp3", music);	//音声の読み込みをリクエスト
			ml.fAddEventListener(comp);				//全読み込み完了後に実行する関数を指定
			ml.fStart();							//読み込み開始
			
			
			
		}
		
	}
	
}

CODE:

package 
{
	import flash.display.Bitmap;
	import flash.display.BitmapData;
	import flash.display.Loader;
	import flash.events.Event;
	import flash.events.EventDispatcher;
	import flash.events.IEventDispatcher;
	import flash.media.Sound;
	import flash.net.URLRequest;
	
	/**
	 * ...
	 * @author DefaultUser (Tools -> Custom Arguments...)
	 */
	public class MyLoader
	{
		private var eveDis:EventDispatcher = new EventDispatcher();
		private var acNum:int = 0;
		
		private var loadedNum:int = 0;					//読み込みが完了した数を示す
		private var reqGraNum:int = 0;					//読み込むべき数を示す
		private var reqGraNames:Array = new Array();	//読み込む画像名を記録
		private var graLoader:Loader = new Loader();	//これを使いまわして画像の読み込みを行う
		private var reqBitmaps:Array = new Array();		//ここに格納すべきBitmapの参照を与え、そこにデータを入れる
		
		private var loadedSouNum:int = 0;				//ダウンロードされた数を示す
		private var reqSouNum:int = 0;					//ダウンロードされるべき個数の上限を示す
		private var reqRealNum:int = 0;					//ダウンロードされるべき個数を示す
		
		public function fLoadedSound(event:Event):void
		{
			loadedSouNum++;
			
			if(loadedSouNum==reqRealNum && loadedNum==reqGraNum) eveDis.dispatchEvent(new Event(Event.COMPLETE) );
		}
		
		public function fLoadedGraph(event:Event):void
		{
			reqBitmaps[loadedNum].bitmapData = (graLoader.content as Bitmap).bitmapData;
			loadedNum++;
			if (loadedNum  0) {
				graLoader.contentLoaderInfo.addEventListener(Event.COMPLETE, fLoadedGraph);
				graLoader.load(new URLRequest(reqGraNames[0]) );			
			}
			
			reqRealNum = reqSouNum;
		}
		
		public function fLoadGraph(name:String, bmp:Bitmap):void
		{
			reqGraNames.push(name);
			reqBitmaps.push(bmp);
			reqGraNum++;
		}
		
		public function fLoadSound(name:String, snd:Sound):void
		{
			snd.addEventListener(Event.COMPLETE, fLoadedSound);
			snd.load(new URLRequest(name) );
			reqSouNum++;
		}
		
		public function fAddEventListener(func:Function):void
		{
			eveDis.addEventListener(Event.COMPLETE, func);
		}
	}
}

CODE:

package 
{
	import flash.events.Event;
	import flash.events.TimerEvent;
	import flash.media.Sound;
	import flash.events.EventDispatcher;
	import flash.media.SoundChannel;
	import flash.media.SoundTransform;
	import flash.utils.Timer;

	/**
	 * ...
	 * @author DefaultUser (Tools -> Custom Arguments...)
	 */
	public class MySound extends Sound 
	{
		private var sndCh:SoundChannel;
		private var timer:Timer;
		private var feedMSec:int;
		
		private function looped(e:Event):void
		{
			sndCh = play();
			sndCh.addEventListener(Event.SOUND_COMPLETE, looped);			
		}
		
		public function loop():void
		{
			sndCh = play();
			sndCh.addEventListener(Event.SOUND_COMPLETE, looped);
		}
		
		private function feed(e:Event):void
		{
			var trans:SoundTransform = sndCh.soundTransform;
			trans.volume -= 30 / feedMSec;
			if (trans.volume < 0)
			{
				sndCh.stop();
				timer.stop();
				trans.volume = 0;
				
			}
			sndCh.soundTransform = trans;
			
		}
		
		public function stop(msec:int):void
		{
			if (msec < 30) sndCh.stop();
			else
			{
				feedMSec = msec;
				timer = new Timer(30);
				timer.addEventListener(TimerEvent.TIMER, feed);
				timer.start();
			}
		}
	}
	
}