Definitely earplugs and maybe even earmuffs in a closed room with a hammer.

I am pretty dang noise sensitive now. I cannot shoot, run saws, bang on steel and other such intense noises without earplugs and muffs.

I would say that the intense concentration of your construction with your head tilted back and noise could have your head screaming for some mercy.

I believe that some noises are to much for the never before concussed head as well but our brain seems to not be as alarmed by the symptoms.

Bud