Almost certainly not by sound, but creating a seal in an ear canal can make it significantly easier to rupture an ear drum. Even a slap up side the head can rupture an ear drum if you get a good seal to their ear before all the trapped air gets crushed. Remarkably easy if it's the second time, I'd know! 20% hearing loss sucks.
Giving him the benefit of the doubt, maybe the alert startled him and he slapped his ear in surprise trying to dig it out. Or maybe stacked on an injury. Or he could always be a weirdo with thin membranes. We're not all clones!