Self-defence perk has tiles hearing range +10. How does that work? Is there actual hearing range modifier? There is nowhere else in the game to see this. Like how much does normal soldier have at the start? If you don’t know that then +10 is not giving you any information.
It is few tiles, like 8 or something like that. So +10 is substantial. Still it only helps you by showing moving red pointer instead of actual enemy. Usually soldier has better perception so he will spot enemy with vision instead of hear. Just a small additional mechanic which prevents situations, where we don’t know about adjacent enemies.