It’s going to be the same logic as for how people are doing area of effect spells, for example. Set a sphere on the character, check for collisions, and adjust the radius of sounds that collide.
E.g. Area of Effect spell/abilities collision handling - C++ Gameplay Programming - Unreal Engine Forums
<edit> Assuming you’re doing single player. If it’s multi-player, it will be a little more complex, as you don’t want players who are near the player with the buff to accidentally benefit from it (of course, you could just call it a bug-as-a-feature: the item’s buff is an AOE buff 
) </edit>