iOS html5 audio autoplay after ajax request

HTML

<div id="initbutton" class="button">Initialize Audio</div>
<div id="ajaxstart" class="button">Start AJAX loop</div>
<div id="console" class="button"></div>

CSS

.button{
    padding: 10px;
    border:2px solid blue;
    margin: 10px;
    cursor:pointer;
}
#console{
    height: 300px;
    overflow:scroll;
    font-size: 90%;
    white-space: nowrap;
}

JavaScript

var con = $('#console');
var sound;
$('#initbutton').one('click',function(ev){
    log("<b>start audio load</b>");
    sound = new Audio("http://localhost/origami/sound/notification/new_incident.mp3");
    sound.addEventListener('canplaythrough',function(ev){
        log('<b>audio loaded</b>');          
    });
    sound.addEventListener('ended',function(ev){
        log('<b>audio played</b>');
    });
    sound.load();
    sound.volume=1;
});

function ajax(){
    log("ajax start");
    $.post('/echo/json/',{a:123435},function(data,status,jqxhr){
        if(sound){
            sound.play();
        }
        log('ajax returned');
    });
};

function getTime(){
    return new Date().toTimeString().substr(0,8);
};

function log(msg){
    con.prepend(getTime() + ': ' + msg + '<br>');
};

$('#ajaxstart').one('click',function(ev){
    log('loop started');
    setInterval(ajax,4000);
});


$('#initbutton').trigger('click');
$('#ajaxstart').trigger('click');