Once you got one that could sample quickly enough and with enough precision, you ought to be able to put it wherever you want, within reason. We did a chrono/sound measurement project when I was at OSU, I'll bust out the report and see how much variance we ended up with shot to shot. The same gun with the same ammo should produce the same amount of sound every time, but since the meter takes readings at finite intervals I think we ended up with something like +/- 3 dB. It was also not a very expensive meter. We knew the results weren't going to be very good going into it, but we did it just for grins and to see what we could actually come up with.
You guys could ask Kurt what they used when he did his thing. I might be able to find out what they use for suppressor ratings.
All it'll tell you though is how much the total amount of sound is pushing on it...humans are naturally more attuned to some frequencies than others, so there's not a perfectly direct correlation between how loud something is, and how uncomfortable it is.