Ajax，jquery和html5声音

so I have very little experience in javascript, jquery or ajax but it seems I need all these things to accomplish what I want to do.

I have a website that gets a full body replacement every minute. within the body is a single html5 audio tag like this:

<audio id='sound'>
  <source src="test.mp3" type="audio/mpeg">
</audio>

once the full body gets refreshed via the jquery, ajax script below I want to play that audio tag.

so I thought I set 2 functions, 1 which reloads the site and 1 which plays the sound. However this doesnt work as ajax is asynchronous. the sound gets played before a refresh.

I have been reading and it seems I need callbacks to do what I want. But through the soup of me having little knowledge of either javascript, jquery and ajax I am just lost..

I have to use a refresh like this because I don`t want to ever end in a site not found or something like that because of a connection error.

Also it seems to me that my full body replacement could use some work as using a regex like that seems rather excessive.

the last connect block is just a small colored block where I can see what was the last state of the website.

<script type="text/javascript">
    function update_site() {
        $.ajax({
            url: "/test",
            dataType: "html",
            cache: false,
            success: function(data) {
                // Replace body with loaded site. You can do more checks here to check
                // if the fetched content is all there.
                var body_html = data.replace(/^[\S\s]*<body[^>]*?>/i, "")
                        .replace(/<\/body[\S\s]*$/i, "");
                $('body').html(body_html);
                $('.last_connect').css('background-color', 'blue');
            }, 
            error: function(data) {
                $('.last_connect').css('background-color', 'red');
            }
        });
    }
    function play_snd() {
        $('.last_connect').css('background-color', 'yellow');
        $('#sound').trigger("play");
    }
// Run every 20 secs.
window.setInterval(function() {
    update_site();
    play_snd();
}, 4000);
</script>