What should I do if my kids argue over the noise level in a shared space?

If your kids argue over the noise level in a shared space -- one child wants to sing and make noise, another child will choose that moment to want or even need silence -- why are you the one having to decide whether there will be singing or silence? Every time you arbitrate that argument for them, you're robbing them of a chance to learn to work it out themselves. Are they going to be yelling at each other? Yes. Will this increase the chances that they yell at each other? Yes. That's when you can be instructive and facilitative.

Ultimately, I think parents rob their kids of life lessons by figuring out their problems for them too often.