Unfortunately, Safari does not support Opus-encoded audio using the Web Audio API. I actually had to push a hotfix earlier this week since Safari uses webkitAudioContext as opposed to AudioContext (which I wasn't checking for) - the site wouldn't even load.
See this issue:
https://github.com/goldfire/howler.js/issues/706
I could fallback to something like MP3, which is something I'm looking into.
I really need to add some type of alert for users using Safari, at least for the time being. Thanks for reminding me!