You can use the tag <audio>in conjunction with JavaScript to play sounds at a given time. Of course, you will need JavaScript, as it is done on the interface, and therefore with client programming.
For instance,
<audio style="display: none;" id="notification" preload src="path/to/soundfile">
Then for scripts, put this somewhere in any part of your script that requires a sound notification:
document.getElementById('notification').play();
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