To see this:
Summon an armor stand.
Run the command
/replaceitem entity @e[type=armor_stand] armor.head acacia_planks
This is quite the opposite of what /replaceitem is supposed to be. It's a technical command, and supposed to replace slots smoothly, unlike /give, which can overflow, and simply summons an item. This noise can happen up to 20x a second, is impossible to get rid of, and obnoxious in multiplayer.
This is likely WAI, but for the sake of having the option of using /replaceitem 20x a second in multiplayer, please change this.
The sound "Gear equipped" is being played.
May be Working as Intended for other workflows.