Shot size makes no difference as far as noise level is concerned. Barrel length,velocity, and muzzle pressure do. Even a .22 Short will hurt your unprotected ears when you first start shooting. When shooting at game or in self defense the sound may not seem nearly as loud, but the damage to unprotected ears is the same. You do not "get used to it", you just go deaf little by little, until you can't hear the shot as well.
On the other hand, looking for ear protection first in a self defense situation may prove counterproductive.
