is the second most common cause of sensory hearing loss Sounds exceeding 85 dB are potentially injurious to the cochlea, especially with prolonged exposures The loss typically begins in the high frequencies (especially 4000 Hz) and, with continuing exposure, progresses to involve the speech frequencies Among the more common sources of injurious noise are industrial machinery, weapons, and excessively loud music Personal music devices (eg, MP3 and CD players) used at excessive loudness levels may also be injurious Monitoring noise levels in the workplace by regulatory agencies has led to preventive programs that have reduced the frequency of occupational losses Individuals of all ages, especially those with existing hearing losses, should wear earplugs when exposed to moderately loud noises and specially designed earmuffs when exposed to explosive noises