Hearing protection devices guard against hearing loss in environments with hazardous noise levels and wherever loud machinery operates. A noise reduction rating (NRR) is assigned to hearing protection to specify in decibels (dB) how much sound is reduced before reaching the ear. OSHA standards call for ear protection that reduces exposure to below 85 dB over the course of an average 8-hour work shift to avoid noise-induced hearing loss (NIHL). Earplugs fit into the ear canal and earmuffs fit over the ears. Earplugs and earmuffs provide similar ranges of protection. Noise-reducing communication headsets and earplugs have electronics that provide one- or two-way communication between workers. Hearing conservation and testing systems train workers on how to correctly use earplugs.