Not to beat a dead horse, but really, have you ever fired a magnum pistol indoors? Most of us HAVE NOT, because of the sound and the flash. It is DEAFENING! Just for fun, practice a few times without ear protection. (Please don't!-I'm just saying it is incredible.)
Anyway, stay safe! In an emergency situation when seconds counts, police are only minutes away...
Take care
Trust me - indoor ranges are INDOORS. Fire at least once a quarter and yes, I know it is loud - even with hearing protection - and big flash. The flash and sound are why I do the range time - so I expect it and not stymied by it if I have to use it in a self defense role.