@simon As I get ready to start using discord more (it seems to be where the real-time action is these days) after hearing @mcc complaining about this problem extensively I am seriously considering buying https://www.rogueamoeba.com/soundsource/ so I can permanently mute it before I start having this experience every day. $40 seems like a lot for a mute button though. perhaps there should be a hashtag to raise awareness, #WhyIsDiscordBeeping
SoundSource - A Superior Sound Control

Access your Mac's audio devices, control per-app audio, and much more, all from the menu bar.