I have a set of Sordin electronic muffs. They are not rated as high as the regular muffs at all. They are adequate for shooting outdoors away from barriers or w/o muzzle brakes.
For shooting near obstacles or around guys with brakes, I double up: ear plugs with the muffs on top. That way the muffs amplify the sounds I want to hear, like a spotter or range officer's commands, but I don't get the blast.
Of course, with some brakes, I feel the blast in my teeth, but that's another matter.
BSW