Occupational hearing loss is a form of acoustic trauma caused by exposure to vibration or sound. Sound is heard as the ear converts vibration from sound waves into impulses in the nerves of the ear. Sounds above 90 decibels (dB, a measurement of the loudness or strength of vibration of a sound), particularly if the sound is prolonged, may cause such intense vibration that the inner ear is damaged. 90 dB is about the loudness of a large truck about 5 yards away. Motorcycles, snowmobiles, and similar engines range around 85 to 90 dB. 100 dB is reached by some rock concerts. 120 dB is a jackhammer from 3 feet away. 130 dB is a jet engine from 100 feet away. A general rule of thumb is that if you need to shout to be heard, the sound is in the range that can damage hearing. Some jobs, such as construction, airline ground maintenance, farming, and jobs involving loud music or machinery, carry high risk for hearing loss . In the U.S., the maximum job noise exposure is regulated by law. Both the length of exposure and the decibel level are considered. If the sound is at or greater than the maximum levels recommended, protective measures are required.
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