With all the above hearing loss stories, I wonder why anyone would use a high-strung magnum as a SD load when a relatively sedate .45 ACP or .44 special would likely do just as well. No point doing excess damage to your ears in a situation where you have a gun prepared for such an event.
http://www.freehearingtest.com/hia_gunfirenoise.shtml
The only gun I shoot regularly (outdoors) without protection is my Marlin .22LR rifle with run of the mill Federal ammo. The sound seems to be well directed away from the shooter and is more like a loud squirt than a bang. My Ruger Mark II .22LR, however, is quite unpleasant and requires ear plugs. I once accidentally let a round of .38 special go (4" barrel I think) and it was quite unpleasant as well.