What is the difference between ER and Non-ER earplugs?
ER rated plugs have been clinically tested to ensure the meet the exacting standards as set out in the EN352-2:1993. Ear plugs with ER filters incorporate individually calibrated filters (usually 9,15 or 25 dB) designed to attenuate all sound frequencies at the same level. Thus giving you a reduced volume but without losing the clarity of what you are listening to. Non filtered plugs give a flat attenuation across the whole frequency spectrum, as a result they give an approximately 30dB attenuation.
