Noise Induced Hearing Loss-with guest author Dr. Gail M. Seigel
Noise Induced Hearing Loss: More than meets the ear
What is noise-induced hearing loss?
Noise-induced hearing loss (NIHL) is a hearing deficit caused by exposure to loud sound. The onset of NIHL can be sudden, as in the case of a bomb blast, or more insidious, as in the case of repeated exposure to loud music or a loud workplace over time. Signs of NIHL may manifest as the inability to hear conversations in a noisy room, acute ear discomfort following loud noise exposure, and/or tinnitus (a ringing sound in the ears). NIHL is a widespread public health issue. According to the Centers for Disease Control, somewhere between 10-40 million people under age 70 in the U.S. have hearing test results suggestive of NIHL. 
How does excessive noise cause hearing loss?
In order to understand how noise causes hearing loss, we need to know a bit about the mechanics of hearing. Under normal conditions, external sounds enter the ear through the auricle, the visible part of the outer ear. From there, the sound waves are funneled through the auditory canal to the tympanic membrane (a.k.a. the eardrum). The tympanic membrane absorbs some of the sound, which causes it to vibrate. These sound waves are conveyed through vibrations that are passed on through the small bones in the middle ear (the malleus, the incus, and the stapes) to the sensitive hair cells of the cochlea in the inner ear. The hair cells of the cochlea transmit the sound wave information as nerve impulses via the auditory nerve to the auditory cortex of the brain for processing and analysis. The end result of auditory processing allows you to distinguish between the sounds of a dog barking and a creaky floor.
Under damaging noise conditions, the cochlea is particularly vulnerable. Exposure to loud noise can lead to a loss of hair cells in the cochlea, degeneration of the auditory nerve, as well as damage to the auditory cortex of the brain. Recent work by our lab has shown that the cochlear nucleus of the brain attempts to repair itself after loud noise exposure . We saw reorganization and repair activities in the cochlear nucleus for at least four weeks following loud noise exposure. Other studies have shown that inflammation can occur in the brain following noise exposure . These experiments and others suggest that even a brief exposure to very intense noise can lead to long-lasting effects, not only in the inner ear but also in the auditory processing portions of the brain. In other words, noise-induced hearing loss involves not only the structures of the inner ear but also the hearing centers of the brain itself.
How to prevent NIHL
The best way to prevent NIHL is to avoid loud noises. Since this is not always possible, there are other strategies you can use to protect your ears from damaging sounds. One option is to keep a set of earplugs with you for rock concerts, sporting events, and other loud venues. If you find yourself in a loud place without ear protection, try to create as much distance as possible between yourself and the source of the loud noise. Spread the word about hearing protection to friends and family, with special attention to young children who may rely on you to protect their sensitive ears.
Evaluation of NIHL
If you suspect NIHL (or hearing loss in general), a hearing health professional can evaluate how well you can hear specific sound frequencies (measured in kilohertz, kHz) and intensities of sound (measured in decibels, dB) in each ear as you listen to various test sounds with headphones. If hearing loss is significant, hearing aids can amplify sounds and improve hearing perception for a better quality of life.
Good luck and may all the sounds you hear be pleasant ones!
By Gail M. Seigel, Ph.D.
Laboratory of Ocular and Auditory Neuroscience
Center for Hearing & Deafness
University at Buffalo
2. Manohar S, Ramchander PV, Salvi R, Seigel GM. 2019. Synaptic reorganization response in the cochlear nucleus following intense noise exposure. Neuroscience Feb 10;399:184-198.
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