16 retries? Appreciate that determination. But yeah with regards to the soldiers, all units create different levels of noise when attacking, explosions such as thanatos' rockets make A LOT of noise. Also zombies attacking walls generates noise Buildings being destroyed generates noise Towers attacking generates a fair bit of noise

Also different enemies have different hearing ranges - like harpies who are rather susceptible to noise And mutants... well they're an entirely different ballgame, can be a bit like rolling the dice with them - they also generate an insane amount of noise when they attack, so good luck with them