Hmm, yeah, it is a bit surprising to me, too, especially for an audio issue, but it’s always possible that you had some weird configuration values in about:config for historic reasons and now some new code, that came in with a Firefox update, isn’t working with that configuration.
Either way, it happens often enough that Mozilla has a troubleshooting routine for it, too, namely refreshing your profile.
If I remember correctly, it places your old profile data into a folder in your Desktop folder. But you can also separately backup your profile by closing Firefox and then copying ~/.mozilla/firefox/ onto an external hard drive or such.