From the general feel of the comments so far, it looks like my opinion will be pretty unpopular, which makes me a bit scared to post this, but I really don't like this law.
Things can sound like a good idea on paper, and often have positive intentions, but when you make a law out of every good idea it can create problems. Every law we make takes away just a little of our freedom (in many cases, a lot). Make murder against the law, I lose the freedom to murder you, and vice versa. That's well worth the cost. But all the little laws like this stack up.
I mean in this case, sure, having a commercial that's loud could inconvenience people, maybe annoy people. And I'm sure it'll make a lot of people happy to not have to deal with it. But as Americans, we don't have a right to not be inconvenienced, to not be annoyed. Of course quieter commercials isn't a really a big deal to us. Maybe it will be more "pleasant." But having a loud commercial be a crime? Really?
Usually when someone says, "You know, there oughta be a law," there shouldn't be.