public void preloadBackgroundMusic(string filePath){
if (_preLoadedAudios == null)
_preLoadedAudios = new Dictionary<string, AudioClip> ();
string ext = Path.GetExtension(filePath);
if(ext!=null && ext.Length>0)
filePath = filePath.Replace (ext, "");
AudioClip audio = Resources.Load<AudioClip> (filePath);
if(audio==null)
CCDebug.Warning ("cocos2d:SimpleAudioEngine: Audio {0} not found.", filePath);
else
_preLoadedAudios [filePath] = audio;
}