rayway, we aren't talking about earplugs.
We are talking about electronic muffs. They can actually be set to AMPLIFY normal sound, but the amplification cuts off when dB exceed a certain point, at which time the muffs act like normal muffs, until the noise abates, and they go back to amplification mode.
You will see a lot of instructors use these when conducting live fire courses. They allow people to converse in normal tones, without removing hearing protection between courses of fire.