Major plotholes left and right undermine the coherence of the dystopian reality

Rating: 5/10 (7 May 2018)

A simple list:
If the creatures rely only on sound (which, already, is odd enough) why are they so LOUD??
Why not go into the basement where noises are sheltered by the mattress?
Why not create ambient noise while away and then return, or just live close to the waterfall for that matter?
Why not have switch to remotely trigger distant speakers from the house, instead of relying on hand-lit fireworks?
Why are the children so goddam stupid? Have they not learned anything from living in this world so long?
WHY DID THEY NOT FIGURE OUT THE BIT ABOUT THE ULTRASOUNDS SOONER???
Too many glaring errors to count... severely undermined my enjoyment of the film.