As an avid gun collector and shooter, while firing a gun without ear protection can be damaging, mostly it would take a LOT of firing a weapon in an outdoor environment to damage the ear drums. As well, firing in doors would speed up that damage. That being said, SCUM did a very good job of noise damage from firing weapons. Depending on the calibre of the weapon fired, if you are firing indoors it will temporarily deafen you and cause you to hear the classic "REEEEEE" sound for a period of time. Using ear protection prevents that, but should also muffle your surroundings.
Ik this is so u can't just run around with a high cal weapon indoors or maybe use hearing protection indoors shoot high cal tactical advantage also it would mean there is strategy to less noisy weapons like crossbow or bow and it would make sense in the game bc survival and u can't just shoot high cal weapons indoors no protection it is way too unrealistic