Ideally this is something we could solve with data, with letting people see the trend over time, with some call to action moments to quiet the fuck down for a minute, reset the otherwise only up-moving gauge.

Every now and then I'll resort to just turning the volume up so that people give up. No, sorry, conversation is already basically impossible except via shouting, so I'm going to up the volume to prevent conversations for a little bit, interrupt the flow, then go back down.

I'd love some volume meters that have very visible displays. It's in the red! Everyone chill out! Or ideally presenting some view over time. Little tablet screens placed about or above that show some logarithmic time scale of volume, so people can calibrate, see the bad trend line. There need to be enough different volume-over-time systems about so people know where the problem really is coming from too. Most people at the party are just trying to talk, so the real art of debugging this nonsense is finding who is being extra loud, and introducing some observability to let the specific worst offenders fix their specific loudness issues, then the rest of the party can de-escalate too.