In the scene at the gas station when Ally is walking the dog and the man approaches with a shotgun to take their car, he tells them to shut the dog up (because noise attracts the creatures/vesps). He then shoots in the air which is considerably louder than the dog barking.
When Hugh throws the tire iron to distract the vesp, it's first by his feet for him to pick up, then he throws it far away, but when the vesp flies towards the sound the tire iron can be seen by Hugh's feet. In the following cut the iron is in the distance again.
The Reverend shows that he and his people have cut off a part of their tongues. Removing the tongue would not guarantee silence. Your vocal cords control sound.
At the 36:47 mark: Miranda Otto's character, Kelly, the mom, signed something but spoke something else at the 36:47 mark. The mom is whispering "Why" but signing the older sign for "What" The subtitles back this up. The line is supposed to be "Why?"
When Hugh and Jude talk to each other at the gas station you can see the camera equipment for the shot of Jude behind Hugh from the car's view. Also either a boom mike or a head disappears behind Hugh and it's not a person since no one appears on the right after that.
Ally says that she "lives in silence, they all do" because she's deaf and they can all speak in sign language, inferring that they have an advantage, but this would not make them completely silent and invisible to the creatures, if anything it would be the opposite because she could make noise, e.g opening a door, and she wouldn't hear it.