I think the old ones are loud, but newer ones can be really quiet. IRC Sweden had one that did well in war games. Gotland class. France also has really modern ones.

Basically they chugachugachugachuga, then go into battery mode and dissappear off sonar. Range is low obviously. Batteries don’t last that long.

Don’t think the Russians have those though. Their navy has been a joke for over a century.