There was a product called 'Sonic II ear plugs' that claimed to have a physical valve that allow normal sound levels to pass through and yet block harmful loud noises. From what I've seen they have been replaced by 'Shooter’s Impact Noise Reducing Ear Plugs' and 'Surefire EP3 Sonic Defender Ear Protection'. The Sonic II style was only rated at NRR 18 which is pretty marginal for gunshot type noise (compare to high end earmuffs with NRR 30). Maybe OK for occasional shots in an open hunting environment, but I wouldn't use it at a range or in an enclosed area such as a blind. Likewise, I wouldn't trust it with a ported 460 etc.
Last edited by Walkingthemup; 01/06/2015 10:50 PM.