Whatever you do you want muffs that have a low profile. Nothing worse than big bulky muffs hitting your rifle stock.
As Hugh also mentioned ear plugs as well.
Shooting under those covered firing lines with a full case of powder and short barrels there is quite the bang even with muffs on.
I can hear range commands with muffs and plugs and my muffs are not electronic. Just a set of low profile Walkers