ACE3/documentation/framework/hearing-framework.md

layout	title	description	group	order	parent
wiki	Hearing Framework	Explains how to set-up headgear with ACE3 hearing system.	framework	5	wiki

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.