The utils.playSound API supports base64 audio now. Try something like
utils.playSound('data:audio/mpeg;base64,SUQzAgAAAAAQP1RUM...AAA')
Unfortunately can't share the entire string due to message size limits but if you need it, DM and I can try different formats.
If you are on iOS make sure the MIME type is accurate or it will not work. Every other platform seems to do type sniffing.