Ha! Awesome idea!What we need is a loudness rating system that's the equivalent of IBU--international bittering units--for hopped beers. How about IGU--international growling units? Maybe Poppy could set up a little sound studio in his shop and we could settle this question once and for all.
In any case, I've never heard an Olson, but a Bellinger G&P is very loud--close, in fact, to the St. John that Klickrolf mentions, though a little throatier.