var sound = SoundCache.getSound("http://hifi-public.s3.amazonaws.com/birarda/boos.wav");

var id = Script.setInterval(function() {
    print("Checking audio...");
    if (sound.downloaded) {
        Script.clearInterval(id);
        print("Starting audio...");
        Audio.playSound(sound, {
            position: { x: 0, y: 0, z: 0 },
            volume: 0.5,
            loop: true,
            localOnly: true
        });
    }
}, 100);