For all hearing protection devices from ear plugs to ear muffs, there is a NRR (Noise Reduction Rating) score that informs consumers how much of a decrease in noise exposure to expect with use. For example, if an ear plug has a NRR score of 30, use of the device would be expected to reduce a 90 decibel sound by 30 decibels resulting in a noise exposure of 60 decibels. If two hearing protection devices are used, an ear plug inside the ear canal followed by ear muffs over the ear, the ultimat…