[redzaku]

Yes, that is the point, electric ear pro turns off when a certain decibel level has been reached. It relies on the cup to provide the hearing protection. That is why slimmer ear pro has lower decibel protection.
If you want to test it out, take your peltor to a gun range and leave on and off your head. There will be some feedback coming from the headset, and when a gun shot goes off you should stop hearing the feedback