Noise-induced hearing loss (NIHL) is a hearing impairment resulting from exposure to loud sound. People may have a loss of perception of a narrow range of frequencies or impaired perception of sound, including sensitivity to sound or ringing in the ears. When exposure to hazards such as noise occurs at work and is associated with hearing loss, it is referred to as occupational hearing loss.
Hearing may deteriorate gradually from chronic and repeated noise exposure (such as loud music or background noise) or suddenly from exposure to impulse noise, which is a short high intensity noise (such as a gunshot or airhorn). In both types, loud sound overstimulates delicate hearing cells, leading to the permanent injury or death of the cells. Once lost this way, hearing cannot be restored in humans.
There are a variety of prevention strategies available to avoid or reduce hearing loss. Lowering the volume of sound at its source, limiting the time of exposure, and physical protection can reduce the impact of excessive noise. If not prevented, hearing loss can be managed through assistive devices and communication strategies.
The largest burden of NIHL has been through occupational exposures; however, noise-induced hearing loss can also be due to unsafe recreational, residential, social and military service-related noise exposures. It is estimated that 15% of young people are exposed to sufficient leisure noises (i.e. concerts, sporting events, daily activities, personal listening devices, etc.) to cause NIHL. There is not a limited list of noise sources that can cause hearing loss; rather, exposure to excessively high levels from any sound source over time can cause hearing loss.
Signs and symptoms The first symptom of NIHL may be difficulty hearing a conversation against a noisy background. The effect of hearing loss on speech perception has two components. The first component is the loss of audibility, which may be perceived as an overall decrease in volume. Modern hearing aids compensate for this loss with amplification. The second component is known as "distortion" or "clarity loss" due to selective frequency loss. Consonants, due to their higher frequency, are typically affected first. For example, the sounds "s" and "t" are often difficult to hear for those with hearing loss, affecting clarity of speech. NIHL can affect either one or both ears. Unilateral hearing loss causes problems with directional hearing, affecting the ability to localize sound.
Temporary and permanent hearing changes PTS (Permanent Threshold Shift) is a permanent change of the hearing threshold (the intensity necessary for one to detect a sound) following an event, which will never recover. PTS is measured in decibels. TTS (Temporary Threshold Shift) is a temporary change of the hearing threshold due to the hearing loss that will be recovered after a few hours to a couple of days. Also called auditory fatigue. TTS is also measured in decibels.
In addition to hearing loss, other external symptoms of an acoustic trauma can be: Tinnitus Otalgia Hyperacusis Dizziness or vertigo; in the case of vestibular damages, in the inner-ear
Tinnitus
Tinnitus is described as hearing a sound when an external sound is not present. Noise-induced hearing loss can cause high-pitched tinnitus. An estimated 50 million Americans have some degree of tinnitus in one or both ears; 16 million of them have symptoms serious enough for them to see a doctor or hearing specialist. As many as 2 million people become so debilitated by the unrelenting ringing, hissing, chirping, clicking, whooshing, or screeching that they cannot carry out normal daily activities.
Tinnitus is the largest single category for disability claims in the military, with hearing loss a close second. The third largest category is post-traumatic stress disorder, which itself may be accompanied by tinnitus and may exacerbate it.
Quality of life NIHL has implications on quality of life that extend beyond related symptoms and hearing ability. The annual disability-adjusted life years (DALYs) were estimated for noise-exposed U.S. workers. DALYs represent the number of healthy years lost due to a disease or other health condition. They were defined by the 2013 Global Burden of Disease (GBD) Study. The DALYs calculation accounts for life limitations experienced because of hearing loss as a lost portion of a healthy year of life. The results indicate the number of healthy years lost by a group of people over a specific time period.
The National Institute for Occupational Safety and Health (NIOSH) used DALYs to estimate the impact of hearing loss on quality of life in the CDC Morbidity and Mortality Weekly Report article "Hearing Impairment Among Noise-Exposed Workers in the United States, 2003-2012." It reported that 2.5 healthy years were lost each year for every 1,000 noise-exposed U.S. workers because of hearing impairment (hearing loss that impacts day-to-day activities). These lost years were shared among the 13% of workers with hearing impairment (about 130 workers out of each 1,000 workers). Mining, Construction, and Manufacturing workers lost more healthy years than workers in other industry sectors; specifically and respectively in those sectors, 3.5, 3.1, and 2.7 healthy years were lost each year for every 1,000 workers.
Negative impacts The negative impacts of NIHL on one's ability to reciprocate communication, socialize, and interact with society are largely invisible. Hearing loss, in general, is not just an issue of volume; individuals may experience difficulty in understanding what is said over the phone, when several people are talking at once, in a large space, or when the speaker's face cannot be seen. Subsequently, challenging social interactions can negatively lead to decreased self-esteem, shame, and fear. This can be more acutely felt by those who experience hearing impairment or loss earlier in life, rather than later when it is more socially accepted. Such psychosocial states, regardless of age, can lead to social isolation, which is known to impact one's overall health and well-being negatively. The compounding impacts can also lead to depression, especially if hearing impairment leads to tinnitus. Research suggests that those with hearing impairment or loss may be at a greater risk for deterioration of quality of life, as captured by a quote from Helen Keller: "Blindness cuts us off from things, but deafness cuts us off from people." Hearing impairment and loss of hearing, regardless of source or age, also limit experiencing the many benefits of sound on quality of life. In addition to the interpersonal social benefits, new studies suggest the effects of nature sounds, such as birds chirping and water, can positively affect an individual's capacity to recover after being stressed or to increase cognitive focus.
Quality of life questionnaire An audiogram typically quantifies the degree of hearing loss; however, the degree of hearing loss does not predict the impact on one's quality of life. The impact that NIHL can have on daily life and psychosocial function can be assessed and quantified using a validated questionnaire tool, such as the Hearing Handicap Inventory for the Elderly (HHIE). The HHIE is considered a "useful tool for quantifying the perceived emotional and social/situational consequences of hearing loss." The original tool was designed to test adults 65 years of age and older; however, modified versions exist. For adults the Hearing Handicap Inventory for Adults (HHIA) can be used and for adolescents the modified 28-item Hearing Environments And Reflection on Quality of Life (HEAR-QL-28) can be used. The HHIA is a 25-item questionnaire that asks both social and emotional-specific questions such as: Does a hearing problem cause you to avoid groups of people?" (social) and "Does a hearing problem cause you to feel frustrated when talking to members of your family?" (emotional). Response options are yes, no and sometimes. A greater score indicates greater perceived handicap.
Cause The ear can be exposed to short periods of sound in excess of 120 dB without permanent harm – albeit with discomfort and possibly pain – but long-term exposure to sound levels over 85 dB(A) can cause permanent hearing loss.
There are two basic types of NIHL: NIHL caused by acoustic trauma NIHL that gradually develops.
Acute acoustic trauma
NIHL caused by acute acoustic trauma refers to permanent cochlear damage from a one-time exposure to excessive sound pressure. This form of NIHL commonly results from exposure to high-intensity sounds such as explosions, gunfire, a drum hit loudly, and firecrackers. According to one US study, excessive noise levels in cinemas are sufficiently brief that movie-goers do not experience hearing loss.
Perceived harmfulness vs. actual harmfulness The discomfort threshold is the loudness level at which a sound starts to be felt as too loud and thus painful by an individual. Industry workers tend to have a higher discomfort threshold (i.e., the sounds must be louder to feel painful than for non-industry workers), but the sound is just as harmful to their ears. Industry workers often have NIHL because the discomfort threshold is not a relevant indicator of the harmfulness of a sound.
Gradually developing
Gradually developing NIHL refers to permanent cochlear damage from repeated exposure to loud sounds over a period of time. Unlike acoustic trauma, this form of NIHL does not occur from a single exposure to a high-intensity sound pressure level. Gradually developing NIHL can be caused by multiple exposures to excessive noise in the workplace or any source of repetitive, frequent exposures to sounds of excessive volume, such as home and vehicle stereos, concerts, nightclubs, factory machinery, and personal media players. Earplugs have been recommended for those people who regularly attend live music concerts. A range of earplugs is now available, ranging from inexpensive disposable sets to custom-fit, attenuated earplugs which provide true fidelity at reduced audio levels.
Personal listening devices Although research is limited, it suggests that increased exposure to loud noise through personal listening devices is a risk factor for noise-induced hearing loss. A systematic review of adolescents and young adults reports that over half of the research subjects had been exposed to sound through music exposure on personal devices greater than recommended levels. Research suggests stronger correlations between extended duration or elevated usage of personal listening devices and hearing loss.
Video game sound levels
A 2024 systematic review of 14 studies investigating associations between sound-induced hearing loss and playing video games and esports found that there was a significant association between gaming and hearing loss or tinnitus, and that the average measured sound levels during gameplay by subjects (which averaged 3 hours per week) exceeded or nearly exceeded permissible sound exposure levels.
Workplace
About 22 million workers are exposed to hazardous noise, with additional millions exposed to solvents and metals that could put them at increased risk for hearing loss. Occupational hearing loss is one of the most common occupational diseases. 49% of male miners have hearing loss by the age of 50. By the age of 60, this number goes up to 70%. Construction workers also have an elevated risk. A screening program focused on construction workers employed at US Department of Energy facilities found 58% with significant abnormal hearing loss due to noise exposures at work. Occupational hearing loss is present in up to 33% of workers overall. Occupational exposure to noise causes 16% of adult disabling hearing loss worldwide.
The following is a list of occupations that are most susceptible to hearing loss: Agriculture Mining Police Construction Manufacturing Utilities Transportation