Added in ACE3 v3.0.0

Hearing Framework

1. Config Values

class CfgWeapons {
    class MyHelmet {
         ace_hearing_protection = 0.80;  // Protection against deafening (0 to 1, higher means more protection)
         ace_hearing_lowerVolume = 0.60;  // Muffling of the sound (0 to 1, higher means more muffling)
    };
};

The protection/muffling is a multiplier and not an absolute value, you can still be deafened/muffled with a value of 1.