Olympus tweaked the sound of the OM-D E-M1 Mark II shutter a little, which will help when shooting in quite places like churches. Even the high speed shooting is pretty significantly muffled compared to the original Mark I.
Olympus OM-D E-M1 Mark II Amazon/B&H Photo/Adorama
Olympus OM-D E-M1 Mark I Amazon/B&H Photo