Understanding noise-induced hearing loss (NIHL): Causes, symptoms, and prevention

We encounter sounds from our surroundings daily—ranging from television and music to household appliances and passing traffic. Typically, these sounds are at safe levels, posing no risk of damage to our hearing.

Understanding noise-induced hearing loss (NIHL): Causes, symptoms, and prevention

Image Credit: Amplivox UK

However, if the sounds are extremely loud or persistent, they can be harmful, even if only temporary. When sounds are both loud and prolonged, it can harm your hearing.

Loud and persistent noises can damage the delicate structures in the inner ear, potentially resulting in noise-induced hearing loss (NIHL). Since this is often a gradual process, individuals may take some time to recognize that their hearing has been affected. The louder the sound, the less time it takes for NIHL to develop.

How noise can damage our hearing

To comprehend how loud noises can harm our hearing, it is essential to understand the process of hearing. Hearing relies on a series of events that transform sound waves in the air into electrical signals. These signals are then conveyed to the brain by our auditory nerve through a complex series of steps:

  1. The sound waves enter the outer ear and travel through the ear canal, a narrow passageway leading towards the eardrum.
  2. The eardrum vibrates in response to the incoming sound waves, transferring these vibrations to three small bones in the middle ear. These small bones are called the malleus, incus, and stapes.
  3. The bones in the middle ear convey the sound vibrations from the air to fluid vibrations within the cochlea of the inner ear. Shaped like a snail and filled with fluid, the cochlea has an elastic partition, that runs from the starting to the end of the cochlea, dividing it into an upper and lower part. This partition serves as the base, or ground floor, for the hearing structure to sit. It is called the basilar membrane.
  4. Once the vibrations cause ripples in the fluid inside the cochlea, a traveling wave forms along the basilar membrane. Hair cells (sensory cells sitting on top of the basilar membrane) ride the wave.
  5. As the hair cells move up and down, microscopic hair-like projections (stereocilia) that settle on top of the hair cells bump against an overlying structure and bend. This causes pore-like channels at the tips of the stereocilia to open, enabling chemicals to rush into the cell and create an electrical signal.
  6. The electrical signal is carried by the auditory nerve to the brain, which translates the signal into a sound that we recognize and understand.

Most NIHL results from the damage and eventual death of these hair cells. In contrast to hair cells in birds and amphibians, human hair cells do not regenerate.

What causes noise-induced hearing loss?

Sound is measured in decibels. Sounds that are at or below 70 A-weighted decibels (dBA), even after prolonged exposure, are unlikely to cause hearing loss.

However, extended or recurrent exposure to sounds at or exceeding 85 dBA can lead to hearing loss. The louder the sound, the shorter the duration required it takes for NIHL to occur. Here are the average decibel ratings of some known sounds:

  • Normal conversation: 60-70 dBA
  • Cinema: 74-104 dBA
  • Motorcycles and dirt bikes: 80-110 dBA
  • Music through headphones at maximum volume, sporting events, and concerts: 94-110 dBA
  • Sirens: 110-129 dBA
  • Fireworks show: 140-160 dBA

How common is noise-induced hearing loss?

The World Health Organization (WHO) approximates that around 360 million people globally experience severe hearing loss and approximately 1.1 billion young individuals (aged between 12 and 35 years old) are at risk of hearing loss due to noise.

According to Healthy Hearing, the world has become so noisy that noise pollution is now regarded as a public health threat.3

What types of noise-induced hearing loss are there?

Noise-induced hearing loss can either be temporary or permanent and may affect one or both ears.

  • Temporary noise-induced hearing loss

This occurs when a person is exposed to a sudden, extremely loud noise. Some common symptoms include muffled hearing, dizziness, and pain in the ear, which lasts for a short period. This is similar to the temporary hearing impairment you may experience following attendance to a loud party or music venue. 

  • Long-term noise-induced hearing loss

This occurs when a person has been exposed to constant loud noises over an extended period. Long-term NIHL often occurs in a noisy workplace environment. Some of the most common industries where employees face long-term NIHL are the military, transportation, construction, and manufacturing.

Some recreational activities involving loud or constant noise can also lead to long-term NIHL. Examples include target shooting, attending music concerts, or regular mowing of the lawn.

What are the symptoms of noise-induced hearing loss?

Symptoms may persist for minutes, hours, or even days after noise exposure ends. Even if the ability to hear returns to its usual state, cells in the inner ear might still face permanent damage. If a sufficient number of healthy cells are left, hearing will eventually recover. However, if more cells are gradually destroyed over time, hearing loss can become permanent. 

As the damage from noise exposure usually happens gradually, it is easy to ignore the signs until they become more noticeable. When attempting to identify the first signs of potential hearing loss, there are a few things to look for. Some of the most common symptoms of NIHL include:

  • Difficulty hearing high-pitched sounds
  • Tinnitus (ringing or buzzing in the ear)
  • Muffled or distorted speech
  • The sensation of fullness or pressure in the ear

How is noise-induced hearing loss treated?

No cure for NIHL exists; however, in many instances, hearing aids can help to address hearing loss issues. If the hearing loss gets progressively worse, hearing aids may become inadequate and surgical methods such as cochlear implants will be suggested. 

Can noise-induced hearing loss be prevented?

Noise-induced hearing loss is among the few forms of hearing loss that is preventable.

A valuable piece of advice is to steer clear of noises that are extremely loud, too near, or last for an extended period. By increasing awareness of the hazards of noise and adapting good hearing health practices, you can safeguard your hearing by taking some simple measures:

  • Be conscious of the noises that can cause damage, so you understand when you must protect yourself.
  • Utilize earplugs or other protective devices during loud activities (activity-specific earplugs and earmuffs are available at most hardware stores).
  • Lower the volume of sounds, such as music and television, whenever possible.
  • If reducing or safeguarding your ears is not possible, try to distance yourself from the source of the sound as much as you can.
  • Take breaks from prolonged exposure to loud noises.
  • Stay vigilant for hazardous noises in the environment and try to distance yourself from them.
  • Safeguard the ears of young children who cannot protect their own.
  • Raise awareness of the hazards of noise to help family, friends, and colleagues.
  • Get your hearing tested promptly if you notice any signs of potential hearing loss.

Help with hearing loss

For additional information and advice on preventing noise-induced hearing loss, you can visit It's a Noisy Planet. Protect Their Hearing®.

Amplivox, as a member of the Hearing Conservation Association, is dedicated to enhancing the hearing health of people globally. Amplivox provides various occupational health courses within audiometry for practitioners dealing with adults with hearing loss issues. These courses offer valuable learning and insight into NIHL.

References and further reading

  1. National Institute on Deafness and Other Communication Disorders (Mar 2022) Noise-Induced Hearing Loss. Accessible at: https://www.nidcd.nih.gov/health/noise-induced-hearing-loss
  2. S. Chadha, S. & A. Cieza (2017) Guest editorial: Promoting global action on hearing loss. World Hearing Day. Accessible at: http://dx.doi.org/10.1097/AUD.0000000000000413
  3. J. Victory (2021) Noise-induced hearing loss (NIHL). Healthy Hearing. Accessible at: https://www.healthyhearing.com/help/hearing-loss/noise-induced-hearing-loss

About Amplivox

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Last updated: Feb 29, 2024 at 6:14 AM

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