I remember some engineer doing tests on youtube. TL;DW: * Double-bagging your ears (plugs + shooting range plugs) seems to help a lot. * With a little more ef

I remember some engineer doing tests on youtube. TL;DW: * Double-bagging your ears (plugs + shooting range plugs) seems to help a lot. * With a little more effort, you can build a handheld shield. Thin, hard layer on top (like plexiglass), which acts like a reflector, then a standard foam layer and cardboard to dampen whatever makes it through the reflector. Besides that, it's not that much different than a water cannon truck or a phalanx shooting tear gas. Confronting both is a relatively high risk activity, and should be avoided by most protesters.