I'm not sure if this is the right place to ask this, but I suppose you guys would be the audio experts. Does anyone here know anything about the NRR system? I work at a golf course, and am surrounded by motorized equipment all day. Anyone who has ever worked a job like this knows that, without some sort of audio entertainment, the repetitive manner of tedious tasks will drive you crazy really quickly. I started using these AO Safety WorkTunes to listen to podcasts on my iPhone. They work okay. The audio quality is pretty bad, but I don't mind that. The noise reduction is rated at NRR 22 dB. I don't exactly know what this number means, just that it is far worse than those little foam earplugs, but certainly better than my Apple in-ear 'noise isolating' headset. I just saw on Engadget these new Etymotic mc2 earbuds. They claim to have the best noise reduction on the market at 42 dB. It says nothing about NRR. Is this important? Are these two numbers directly comparable? Is it safe to say that the mc2s eliminate nearly twice as much sound as the big earmuffs? Will they be twice as quiet as the earmuffs? I have a hard time believing that the Etys do a better job of reducing noise than these standard industrial earplugs, rated at NRR 33 dB. Again, are the numbers comparable? Is 42 dB > NRR 33 dB? If not, how would the Etys compare to these two other ear protectors? Again, I know nothing about noise reduction, so any insight would be welcome.