The filtering takes place on the receiving end for certain devices...ie electronic earmuffs.
Police handhelds, the mic and speaker are in one unit. Take a look at the next cop you see and they have a cord from their radio to the mic/speaker that is clipped to their shoulder or chest. It’s all in one.
Two different things.
Go to a gun range and use ‘noise canceling’ earmuffs. You can have a perfectly clear conversation, hear everything, hear the beep of the timer, once the gun goes off the electronics cancels out the noise.
It’s not possible to have that on a handheld radio with the mic/speaker hanging off your body somewhere.
Guess I better tell my company to stop using the mics that work while I’m standing next to a ten story boiler in a paper mill..? I USE THEM EVERYDAY!!!!!