The source code

    /**
     * @class Ext.air.Sound
     *
     * @singleton
     */
    Ext.air.Sound = {
    	/**
    	 * Play a sound.
    	 * @param {String} file The file to be played. The path is resolved against applicationDirectory
    	 * @param {Number} startAt (optional) A time in the sound file to skip to before playing
    	 */
    	play : function(file, startAt){
    		var soundFile = air.File.applicationDirectory.resolvePath(file);
    		var sound = new air.Sound();
    		sound.load(new air.URLRequest(soundFile.url));
    		sound.play(startAt);
    	}
    };