Noise-Induced Hearing Loss
Noise-Induced Hearing Loss
By Stanley Pelosi, MD
What is noise-induced hearing loss?
Noise-induced hearing loss (NIHL) refers to a permanent hearing impairment from exposure to loud sounds. Of all causes of hearing loss, noise is the major preventable cause. Learn more about
How common is noise-induced hearing loss? Whom does it affect?
The most common cause of NIHL is thought to occur due to workplace exposure to loud sounds, with an estimated 10 million Americans at risk from occupational-related NIHL. Other less common causes include noise exposure from recreational activities such as shooting sports, music concerts, and listening to portable music players at high volume. Overall, a greater percentage of males compared with females are affected by NIHL. Individuals of any age can be affected by NIHL, and the risk is not known to be higher in young or old patients.
What causes noise-induced hearing loss?
Sounds are measured in units called decibels (dB). Most sounds under 75 dB (normal conversation, kitchen appliance noise) are unlikely to cause NIHL. However, sounds above 85 dB have the potential to cause damage to hearing structures. This may include brief, extremely loud noise “impulse” noises such as gunshots, explosions, or sirens. Continuous sounds of moderately loud intensity, frequently encountered in the workplace environment or with use of portable music players, can also result in NIHL.
Excessive noise causes damage to inner ear sensory cells, known as hair cells. These cells receive the energy from sound waves that reach the eardrum and convert them to nerve signals that travel to the brain. Loud noises can damage hair cells through mechanical injury and cause their eventual death, leading to permanent hearing loss.
Who is at risk for noise-induced hearing loss?
Any individual exposed to excessive noise is at risk for NIHL. As described above, this may include industrial workers who are exposed to continuous, loud workplace sounds, or it can include individuals exposed to impulse noises while participating in recreational activities.
How is noise-induced hearing loss diagnosed?
NIHL is suggested by hearing loss in an individual with a history of exposure to loud sounds. The hearing loss can be temporary (lasting one to two days after a loud concert, for example), or it can be permanent. Hearing loss may also be gradual so as to go initially unnoticed. Individuals with NIHL frequently complain of ringing or buzzing noise in their ears (tinnitus) in addition to hearing loss. Recent research has shown that chronic noise exposure can worsen complaints of fatigue and irritability.
Diagnosis of NIHL is suggested in patients who on a hearing test (audiogram) demonstrate hearing loss. The hearing loss is sensorineural in nature (which means stemming from problems in the inner ear or the auditory nerve), and may disproportionately affect specific sound frequencies (3,000 Hz, or in the high frequencies). No laboratory or imaging studies are specifically indicated for diagnosis of NIHL, although they may have use in evaluating for other causes of hearing loss.
How can noise-induced hearing loss be prevented, and what are treatment options?
Prevention of NIHL first requires identifying the environmental sounds that can cause hearing damage (those above 85 dB). In cases where exposure to these sounds cannot be avoided, hearing protection is necessary. This may include protective devices such as earplugs or earmuffs that can dampen environmental sound intensity. The Occupational Safety & Health Administration (OSHA) has required that for workplaces where sounds exceed 85 dB, employers must implement a hearing conservation program that includes provision of free hearing protection devices.
There are currently no medical treatments available to reverse the damage caused by NIHL. For those with significant hearing loss, hearing aids and assistive listening devices (such as frequency modulation, or FM, systems) can provide benefit in amplifying environmental sounds.
The natural history of noise-induced hearing loss is variable. Some patients may exhibit no change, while others may experience worsening of hearing due to persistent noise exposure and/or concurrent age-related hearing changes.
What research is being done on noise-induced hearing loss?
There are several active areas of research on NIHL. One involves further examination of the causes and sites of hair cell damage in these patients. Another involves examination of genes and proteins that may have a protective effect in preventing NIHL caused by noise-related trauma.
Where can I get more information on noise-induced hearing loss?
Stanley Pelosi, MD, is an assistant professor in the Department of Otolaryngology – Head and Neck Surgery at The New York Eye and Ear Infirmary. Dr. Pelosi graduated with a degree in neuroscience from Brown University, and earned his medical degree from Brown Medical School. He completed residency training in Otolaryngology–Head and Neck Surgery at the Mount Sinai Medical Center. Dr. Pelosi then went on to complete a two-year fellowship in Otology/Neurotology at Vanderbilt University Medical Center.
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