Thanks for the numerous replies. There doesn't seem to be a clear correlation between strong side shooting and hearing loss in that ear, but I do value the data regardless.
I've been doing some research into measuring gunfire noise pressure levels and it's not easy to measure (or inexpensive) due to the short duration and high amplitude of the pressure wave. I'd like to do some real-world testing of my own, without sacrificing my own hearing or investing mega-bucks in testing equipment.
At the moment my game plan would be to have a shooting buddy (with good hearing protection) do the shooting while I stood some relatively safe fixed distance behind to subjectively judge which firearm/ammo combination was more ear friendly. This could also be done, of course, standing to the side to have an indication of the relative effects on a bystander.
I've seen some charts (http://www.freehearingtest.com/hia_gunfirenoise.shtml
for example) but don't know how the data was measured (distance or relative position of the sensor, for example). Ammo has to make some difference as well - I would like to be able to know (hear) the relative difference between a .38 special wadcutter target load and an FBI load +P from the same gun.
I hope to be able to finish my testing by the end of the year and will publish anything of value, of course, on TFL.