A Noise Reduction Rating (NRR) measures the amount of hearing protection or attenuation provided by different hearing protectors. Measured in decibels (dB), the NRR of a hearing protector must be determined in a lab and approved by theAmerican National Standards (ANSI) in accordance with theOccupational Safety & Health Administration(OSHA). ISOtunes products use industrial grade memory foam to block 22-29 dB of damaging noise, which means you can work in loud environments knowing your ears are protected.