I have a relative I want to introduce into shooting, but they have problems with loud sounds. I took them once before and they did okay, before a guy in a stall next to us starting mag dumping his AR. Point being they sound to freak out just a bit, so I'm wondering if there's any muffs that really dampen sound a lot. Like a LOT. Any recommendations would be appreciated, thanks.

Edit: thanks for all the suggestions, and especially thanks for not just saying 'tough shit don't let them shoot a gun then'