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Have you ever heard a ringing in your ears after a loud concert? Did sounds seem muffled? These could be early signs of permanent hearing loss. Constant or even occasional loud noises can damage your hearing beyond repair. More than 35 percent of the 28 million cases of hearing loss in the United States are caused, at least in part, by exposure to hazardous noises. Hazardous noise can be anything from loud music to the sounds of a lawn mower. To find out how hazardous a sound is, we measure its loudness in decibels, which tell us its power or intensity. The decibel scale is logarithmic - each 10-dB increase is a factor of 10. The normal human ear can hear sounds down to 0 dB. The roar of a rocket lifting off registers over 140 dB. Experts consider noise levels above 85 dB hazardous, particularly when you're exposed to them for long periods. The louder the noise, the less time it takes to damage your hearing. Many rock concerts are 110 dB or more. If you attend often, you can damage your hearing before you know you are in danger. The ear has three parts - the outer, the inner, and the middle ears. The outer ear includes the visible part outside our head and the ear canal, which ends at the eardrum. The middle ear contains three tiny bones called ossicles. The inner ear contains the cochlea, housing thousands of hair cells and nerve endings. When sound waves travel down the ear canal and strike the eardrum, it vibrates. This causes the ossicles to vibrate. The sound is then transmitted to the inner ear. Vibrations set the fluid within the cochlea in motion, stimulating the hair cells. The movement of the hair cells stimulates the auditory nerve endings, which send the sound pattern to the part of the brain that interprets it. Hearing problems in the outer and middle ears can cause conductive hearing loss. An example is otitis media, fluid in the middle ear caused by infection. These problems can often be corrected with medicine or surgery. Sensori-neural hearing loss is usually permanent and is caused by damage to hair cells in the inner ear. When hair cells or auditory nerves are destroyed, they cannot be repaired. Loud and persistent sounds can damage hair cells and cause permanent hearing loss and tinnitus. Next time you listen to music, keep the volume low and rest your ears often. Use earplugs at concerts. Remember, once your hearing is damaged by loud noise, it's gone forever!
