Walker’s new Punisher edition Razor Slim Electronic Muff has a Noise Reduction Rating (NRR) of 23 dB, and utilized sound-activated compression (SAC) of 0.02 seconds. SAC is a special electronic circuitry that will compress gun shots and other loud noises down to a safe level, without completely shutting the noise off. This allows you to hear range commands or communicate with your shooting or hunting partners, even when shots are being fired around you.