I dunno, but I'm beginning to think that the best defense against being car-jacked is a manual transmission.
what is this all about with you Americans loathing manual transmission?
Back on topic:
in confined spaces, I reckon you can get serious hearing damage from a .22 as well, particularly if it's a wheelgun with the cylinder gap adding a few dB to the bang, as someone has already pointed out above. The only solutions would be 1.) a can or 2.) the use of special ammunition for in-room-training which produces clearly lower sound levels. The problem with the latter is that its terminal ballistics are even more questionable than with standard .22lr loads, around 60 joules instead of 110, depending on barrel lenght. (44 instead of 81 lbs/ft, to stay imperial...).