I am not exactly sure how the electronics work, but I have never heard of any of the guys who use them (nearly all use them who I shoot competitively with) ever have a 'bang' amplified.
What they do is amplify sound (really cool when you are wearing plugs and can't hear anything). If you are outside wearing plugs and the muffs with the muffs turned on, you can hear a squirrel and leaves rustling in the distance.
Then whenever a sound is encountered that is too loud (you can trip them with a loud clap of the hands), the electronics are turned off and then you get the sound muffling of the muffs as well as plugs.
I always use them. Unless I am alone and am shootings my .22 only. Then I might use one or the other of plugs or muff.