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Since 1988 uniform (flat attenuation) earplugs have been available for those in the audio industry and in the performing arts. With the introduction of the ER-15 musicians’ earplug from Etymotic Research (ER)
based on the work of Elmer Carlson and Mead Killion, custom made ER15 earplugs have been the mainstay in the industry. These custom-made earplugs attenuate all sounds equally between 63 Hz and 8000 Hz (but with a 3-4 dB dip in the 6000 Hz region). Music can now sound like music, only a safe and more comfortable level.