So, here's an update...I left the Apple store, having left my watch with them, feeling like they were just going to tell me it was not repairable. Pretty crappy feeling. Several days later, I got it back in the mail and it worked again! The sound was great and no problems with it whatsoever. Also, no explanation of what they did or what was wrong. While my watch was with Apple, I did some digging on the internet. It seems a whole lot of people are having the same trouble with their Apple watch 10's. Here is what I gleaned from this whole ordeal: Take your watch off if you are washing your hands with soap, or putting on lotion, or those kinds of things where things can get in those tiny little holes along the side of your watch. The Apple watch 10 is thinner that the watches ever have been and the speaker is right behind those little holes. Anything clogging those tiny holes effects the speaker. When the Apple folks were grilling me about how I use my watch, they continually asked me about water and this puzzled me because it is supposed to be waterproof. This was my first clue. They are definitely having trouble-not with water, but other things getting in the little holes.
Since I got my watch back, I am super careful not to get anything on it. I take it off when I am doing dishes, washing my hands, putting on lotion, etc... I recommend doing this so you don't encounter the problems that I have had. I wish you all the best of luck with your 10's.