One in 10 Americans suffers from a loss of hearing that affects his or her ability to understand normal speech. Excessive noise exposure is the most common cause of hearing loss, especially for those from ages 21 to 35. The damage caused by noise, called sensorineural hearing loss or nerve deafness, can be caused by several factors other than noise, such as aging or viral infections. Noise-induced hearing loss is different in one important way: it can be reduced or prevented altogether.
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To understand noise-induced hearing loss, it is important to look at how the ear functions. The ear is separated into 3 main sections: the outer, middle, and inner ear. The outer ear is the part you can see, which opens into the ear canal. The tympanic membrane, also known as the eardrum, separates the ear canal from the middle ear. The small bones of the middle ear (malleus, incus, and stapes) help transfer sound to the inner ear. Within the inner ear, a complex system of ear fluids and receptors leads to the stimulation of the auditory nerve, which leads to the brain.
Any source of sound sends vibrations or sound waves into the air. These funnel through the ear opening, down the ear canal, and strike your eardrum, causing it to vibrate. These vibrations are passed to the small bones of the middle ear, which transmit them to the hearing nerve in the inner ear. Here, the vibrations become nerve impulses and go directly to the brain, which interprets the impulses as sound, whether it be music, a slamming door, a voice, or etc. When noise is too loud, it begins to kill the nerve endings in the inner ear. As the exposure time to loud noise increases, more and more nerve endings are destroyed. As the number of nerve endings decreases, so does your ability to hear. Currently there is no way to restore life to dead nerve endings; the damage is permanent. Various studies are underway to better understand noise-induced hearing loss and from that, find a cure.
Signs of noise-induced hearing loss include asymmetric hearing loss, tinnitus (ringing sound in the ears), dizziness, and headaches. When hearing impairment begins, the high frequencies are usually lost first, which is why people with hearing loss often have difficulty hearing the high-pitched voices of women and children. Loss of high frequency hearing can also distort sound, making speech difficult to understand even though it can be heard. People with noise-induced hearing loss often have difficulty detecting subtle differences between certain words that sound alike. This is most common in words that contain S, F, SH, CH, H, or soft C sounds, because the sounds of these consonants are at a much higher frequency range than vowels and other consonants. If any of these signs or symptoms sound familiar to you, you may want to head over to an audiologist to have your hearing formally evaluated with an audiogram.
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