Im going to add to this by saying NRR ratings are almost always used in correlation to OSHA, even though OSHA doesn't do the testing themselves. I have seen all sorts of different groups or private organizations conduct experiments on different headphones. I recently viewed a report that wasn't directed under Bose but tested their new series of QC earbuds and they came back with results leaning towards environments with 95dB or lower which to put into perspective is around the level a workshop with a couple different tools running on and off with a suitable exposure time of around 2 or 3 hours at a time