Despite being a glaring departure from rationality, monsters are surprisingly rule-governed creatures. Some monsters are afraid of the light. Some monsters can only get you when you're dreaming. Some monsters only kill horny teenagers at summer camp. In this film, the monsters are reincarnated librarians or perhaps those neighbors always calling in noise complaints, because they only kill people who make noise. Rules is rules. The rule here is "Be Quiet!"
It is easy to imagine the writer's room on this one.
1: Hmm, how do we do dialogue without speaking?
2: Uh, they use sign language?
1: OK, how is it that our American family is proficient in sign language.
2: Uh, they had a deaf kid and had to learn it.
1: How'd they kill the monsters in War of the Worlds?
2: Uh, germs? Right! Except this time the reversal will be deafness.
1: The deaf kid will secretly be super powered with her hearing aid!
Come to think of it, isn't it amazing how alien invaders so often have a simple silver-bullet weakness?
Our family is remarkably kitted out for the apocalypse given that just about everyone else seems to be dead. They've got electricity, crops, waters, a light-signaling system, bare-foot(able) paths, etc. They've really got it worked out. You get the sense that that writers room was in overdrive spinning copious details. All of this is to the good.
In the end, it turns out that the creatures can be killed with a 12 gauge (?!?), however, so it makes you wonder why the human race lost so hard. There are more guns than people in the United States, so you would think that someone would've figured out that the monsters aren't bullet proof. The monsters move fast but are not invisible and offer a very broad target when they're in skulk-mode. You'd think that gun ships would be able to pick out the heat signatures of these things and pick them off. But it doesn't matter all that much. Somehow they appeared out of nowhere. Somehow the human race was quickly defeated. Somehow these things are everywhere. That's just how it is. It isn't rational. But there are rules. And the no noise rule makes for a marvelous exercise in suspense. When people finally do scream it is as much an emotional release as it is a terrible escalation. The film is great for this conceit alone. It simply works.