Question: Where is the mailbox with the Abbott's name on it?
Question: How do the alien creatures orientate? They're blind but sensitive to noises, so I guess it is supposed to be some kind of echolocation - but first, echolocation is not a way of "seeing" your environments constantly, especially not suitable for running like crazy in a forest full of trees and obstacles. Second, by using echolocation, they should be able to locate moving objects even it's noiseless. So how?
Answer: It's not known that the creatures are blind, just known that it isn't their primary sense. Bats use echolocation but (contrary to popular belief) aren't blind.
Question: Why don't they just abandon the place and go to somewhere safer?
Answer: Such as where? They live in what is presumably their house, with all their belongings. Uprooting and walking silently to a new location to set up a new home would be more dangerous than staying where they are.
Question: Why not live underground most of the time and only emerge when necessary?
Answer: That's essentially what the family is trying to do. They come up for supplies and to use the radio to try and reach the outside world. They built the basement area and used what supplies they had for soundproofing.
Answer: Unsurprisingly, there weren't any underground living spaces nearby, and creating one would generate sound.
Question: If the waterfall prevents the creatures hearing them, why not live there?
Question: The daughter already found out about her cochlear implant giving off a frequency that scared the aliens away, so why did she not turn it on when they were in the truck? If she had, Lee would not have had to sacrifice himself.
Answer: People don't always consider every possibility when they are scared.
Question: How did they climb the grain silo without making noise? Why did the silo door come off its hinges?
Answer: 1. Quietly. 2. The hinges weren't able to support the weight of the swinging door that was meant to open outward.
Answer: While Lee and Marcus are at the river with the fish traps, Lee begins explaining to his son about safe sounds. It then cuts to Regan walking away from her house, and in the next wide shot facing Regan, the Abbott family mailboxes are on the left side of the screen, with their house in the background (00:36:27).
Super Grover ★