I doesn't know if it works for mobile, but the plain html5 audio tag has an autoplay attribute.
<audio controls preload="auto" autoplay>
<source src="./sfx/ok.ogg" type="audio/ogg">
<source src="./sfx/ok.mp3" type="audio/mpeg">
<source src="./sfx/ok.wav" type="audio/wav">
<source src="./sfx/ok.mp4" type="video/mp4; codecs=avc1.42E01E,mp4a.40.2">
Your browser does not support the audio element.
</audio>