[gmiller123456]

In addition to canceling sound, the headphones actually block a lot of it to begin with, so they only have to cancel what's left. On the gun range, it's pretty popular to use quite the opposite of noise canceling headphones. They actually amplify sounds at normal human speech levels, then cut off anything above a certain amount. They make no attempt to cancel the gunshot sounds, they just don't reply them inside the headphones. And the blockage from just the physical headphones is enough to turn a deafening gunshot into something fairly comfortable to listen to for quite a long time.