Solution #1

My solution was to create an iframe

<iframe src="audio/source.mp3" allow="autoplay" style="display:none" id="iframeAudio">
</iframe>

and audio tags for non-Chrome browsers

<audio autoplay loop  id="playAudio">
    <source src="audio/source.mp3">
</audio>

and in my script

var isChrome = /Chrome/.test(navigator.userAgent) && /Google Inc/.test(navigator.vendor);
  if (!isChrome){
      $('#iframeAudio').remove()
  }
  else {
      $('#playAudio').remove() // 为了确保背景中不会有两个音频
  }

Solution #2:

According to @Leonard, there is another solution

Create an iframe that doesn't play anything, just to trigger autoplay on first load.

<iframe src="silence.mp3" allow="autoplay" id="audio" style="display: none"></iframe>

Good mp3 file source: silence.mp3

Then play your real audio files easily.

<audio id="player" autoplay loop>
    <source src="audio/source.mp3" type="audio/mp3">
</audio>

Personally prefer Solution #2 as it is a cleaner approach and less dependent on JavaScript.

Updated in August 2019

Solution #3

As an alternative we can use <embed>

ForFirefox It seems audio autoplay is working so we don't need the <embed> element as it will create two audios running at the same time.

// index.js
let audioPlaying = true,
    backgroundAudio, browser;
browser = navigator.userAgent.toLowerCase();
$('<audio class="audio1" src="audio.mp3" loop></audio>').prependTo('body');
if (!browser.indexOf('firefox') > -1) {
    $('<embed id="background-audio" src="audio.mp3" autostart="1"></embed>').prependTo('body');
    backgroundAudio = setInterval(function() {
        $("#background-audio").remove();
        $('<embed id="background-audio" src="audio.mp3"></embed>').prependTo('body');
    }, 120000); // 120000是你的音频持续时间，本例中为2分钟。
}

If your audio has a toggle event, make sure to delete the <embed> element you created.

NOTE: After the switch it will start from the beginning since <embed> has been removed and the <audio> element will now play normally .

$(".toggle-audio").on('click', function(event) {
    audioPlaying = !audioPlaying;
    $("#background-audio").remove();

    clearInterval(backgroundAudio);
    if (audioPlaying){
        $(".audio1").play();
        // 播放音频
    }
    else {
        $(".audio1").pause();
    }

Now make sure to hide these <audio> and <embed>elements

audio, embed {
    position: absolute;
    z-index: -9999;
}

Note: diplay: none and visibility: hidden will make the <embed> element not work.