Non NFA Noise Mitigation For Defensive Rifles?

[Saladfarmer]

On a bolt gun it may help, the shooter, like what Pat is shooting in the video. AR, it's not going to make much difference at all, especially inside as stated by many of you. This video is a couple years old as I recall. Saw it when it came out back then. There are several makers of equivalent devices, all function the same. Aluminum or steel. It's not quieting anything, just "redirecting" as stated. Get a can if you're concerned about your ears. Or a cross-bow.
Act accordingly.