Hearing protectors.
D003142:Communication; D004430:Ear Protective Devices / Q000592:standards; D005069:Evaluation Studies as Topic; D006260:Head Protective Devices; D006309:Hearing; D006317:Hearing Loss, Noise-Induced / Q000517:prevention & control; D006801:Humans; D009622:Noise; D011482:Protective Devices / Q000592:standards; D012015:Reference Standards