What Episcopus says below agrees with my anecdotal evidence/personal experience.
I'm not sure that a meaningful numeric rating system is possible. We know sound intensity and sound level have a logarithmic relationship [sound level = 10 log (I/I_o) on the decibel scale], so to add the complications of the baffled plugs ... well, as a former US EPA employee, I am . . . not confident . . . that they or their contractors can do much of anything right.
The bottom line is that the Sonic Defenders work great for protecting your hearing from high intensity sounds with a sudden pressure/intensity spike like gunshots. They're not great for lower intensity, constant, but still potentially damaging noise. For the latter situations, good foamy earplugs rule!
I'm not sure that a meaningful numeric rating system is possible. We know sound intensity and sound level have a logarithmic relationship [sound level = 10 log (I/I_o) on the decibel scale], so to add the complications of the baffled plugs ... well, as a former US EPA employee, I am . . . not confident . . . that they or their contractors can do much of anything right.
The bottom line is that the Sonic Defenders work great for protecting your hearing from high intensity sounds with a sudden pressure/intensity spike like gunshots. They're not great for lower intensity, constant, but still potentially damaging noise. For the latter situations, good foamy earplugs rule!
I have these too. The NRR with them unplugged is 9, plugged is 16. The problem is that the attentuation in hearing protection like this is non-linear. The more intense the noise, the greater the reduction. I think the chart that comes with them shows something like a 36db reduction at 120db. I think the EPA is reworking the NRR scale to better test the non-linear systems, as plugs like these seem to be getting more popular.
I can shoot all day on the outdoor range with absolutely no discomfort. On the indoor range, I usually put the plugs in to up the protection, but I have gone with them out and not had any discomfort. I am very impressed with the protection these offer.