audio trigger sound issue

It will play mail sound after click play button, and play shutter sound after 2 seconds, but on mobile it's only play mail sound, I thought audio play only trigger by real click behavior, how to trigger browser play the sound with out really click on the element.

HTML

<input type="button" id="play" value="play">
<audio id="mail" src="http://chan15.info/question/sound/mail.mp3" preload="auto" type="audio/mp3">
<audio id="shutter" src="http://chan15.info/question/sound/shutter.mp3" preload="auto" type="audio/mp3">

JavaScript

$('#play').on('click', function() {
    $('#mail').trigger('play');
    
    var $time = setTimeout(function() {
        $('#shutter').trigger('play');
    }, 2000);
});