Understanding Noise-Induced Hearing Loss

June 19, 2020

Understanding Noise-Induced Hearing Loss
 
Dr. Darcy Benson

In people who have experienced hearing loss, one of the most common types they encounter is noise-induced hearing loss (NIHL). According to the American Hearing Loss Foundation,NIHL is one of the most common types of hearing loss in the US, after age-related hearing loss.

NIHL is a kind of sensorineural hearing loss and occurs in 23 percent of people over the age of 65. Unlike all other forms of hearing loss, hearing loss caused by noise can be avoided altogether. Here, we look specifically at a hearing loss caused by noise, the causes, and what can be done to prevent it.

 

How the hearing system works

Our auditory system serves one of our body’s most complex and fascinating functions. To better understand the noise-induced hearing loss, a basic understanding of how good hearing works is essential.

  1. Sound waves pass through the ear canal to enter the ear.
  2. These sound waves travel to the eardrum through the ear canal. Eardrum vibrations move three tiny bones in our middle ear; these bones are called the malleus, incus, and staples, and are the smallest bones in the body.
  3. The vibrations of these tiny bones cause fluid to ripple and wave in our cochlea. The cochlea is in the inner ear and is a fluid-filled snail-like organ.
  4. Our inner ear fluid movement causes small, delicate hair-like cells to bend and sway above the liquid.
  5. These hair-like cells bend, which transmits the sound waves into electrical signals.
  6. Finally, these signals are sent to our minds for processing via our auditory nerve. 
  7. Our brain then interprets and understands these signals as sounds.

 

How loud is too loud?

Any sound that is below 85 dB (from listening position) is considered safe. The permanent hearing loss sets in at 85 dB after about 8 hours of treatment. The amount of time it takes for hearing loss to happen cuts in half for every three dB increase in volume. This means a 91 dB sound will take just 4 hours to cause damage to your hearing and only 2 hours at 97 dB.

To give you some perspective, here are some familiar sounds and their dB equivalent:

  • 70 dB: Washing machine
  • 80 dB: Alarm clock
  • 90 dB: Subway train cart
  • 100 dB: Factory machinery
  • 110 dB: Car horn
  • 120 dB: Live music concert

 

What happens when we get too much sound

Loud noise exposure can damage the inner ear, especially the cochlear hair cells. The louder the sound, the more vibration it causes the cells of the hair to move and bend. The sheer volume of the soundwaves can start to damage the hair cells physically. Such damage will cause the cells to lose sensitivity and function less effectively.

This is how most of us experience a loss of hearing over the short term. Muffling of your hearing is normal after leaving a concert or other noisy event. You might speak loudly; you may need others to speak loudly to hear them. This is mainly because the cochlea’s hair cells have been drained by all the excessive noise you received. Your hearing typically returns after a short period, because your ears have rested.

If someone is exposed to loud noise regularly, and the hair cells do not have time to rest, the effect can be severe. In contrast to other cell types, the hair cells do not regenerate. We are born with every hair cell we’ll ever have. When they are damaged, we can’t ever get that hearing back. 
 

How to prevent noise-related hearing loss

We can do several things to reduce the level of sound that reaches our ears. 

Increase your distance. The best is to step away from the origins of loud noises physically. Your exposure falls by six dBA for every doubling of the distance between you and the source of the sound. 

Reduce the length of exposure. Likewise, we can restrict our exposure. Although dangerously loud sounds should never be experienced without hearing protection, many other sounds cause NIHL only after prolonged exposure.

Use hearing protection. We should use hearing protection if we have to (or choose to) be exposed to noisy noises for longer than is necessary. It’s a good idea to carry general-purpose earplugs wherever you go if you find any sound that you want to block.

Monitor sound levels around you. Cell phone apps are now available for download, which can measure dB levels. When you’re unsure of the noise level of an environment, you can use the app to determine if it is time to get the earplugs out.
 

Treating hearing loss induced by noise

When you already suffer from NIHL, the damage is permanent. Nevertheless, hearing aids have been repeatedly proven to help treat this condition. Hearing aids amplify the sounds around you so you can hear more easily. They will not completely correct your hearing like glasses can do for your eyes, but they have helped millions worldwide improve their hearing. 

If you believe that you’re struggling with noise-induced hearing loss, please contact us today to set up a hearing test and get back to hearing again.