Noise-Induced Hearing Loss: Causes, Signs, Symptoms, Treatment, Pathophysiology, Prevention

What is Noise-Induced Hearing Loss ?

Can you imagine our world without any sounds or noises and only just pin drop silence? No, right? Our world is a myriad full of sounds; the sounds when we talk, the sound of engine revving, automobile sounds, sounds of instruments, sounds blaring from television, stereo speakers and our smart gadgets etc. All these sounds are a part of our daily life and we basically have become used to it and don’t even notice all these sounds in our busy world. All these sounds, which we hear on a day to day basis are at safe levels and pose no threat to our hearing. However, there are certain sounds when they are very loud, though it can be for fleeting seconds or some minutes, can wreak havoc on our hearing.(8) Such type of loud sounds damages the sensitive structures of our inner ear and lead to what we term as Noise-Induced Hearing Loss (NIHL). People Affected by Noise-Induced Hearing Loss (NIHL)

People of any age, including children, adults and older individuals, can be affected with noise-induced hearing loss due to exposure to harmful and loud noise. According to studies, there are a high percentage of people with features on their hearing test indicative of hearing loss in both the ears or one ear due to exposure from loud noise.(8)

The Pathophysiology of Noise-Induced Hearing Loss(8)

In order to understand more about noise-induced hearing loss, we need to understand our normal hearing process. Our hearing depends on a chain of events that alter the sound waves in the atmosphere into electrical signals. The auditory nerve then transmits these signals to our brain following a complex series of steps. These sound waves then enter the outer ear and pass through the ear canal leading into the eardrum. As a result, there is vibration in the eardrum from the entering sound waves and these vibrations are transmitted to the three tiny bones located in the middle ear.

These small bones connect sound vibrations to fluid vibrations in the inner ear in cochlea, which is filled with fluid. The cochlea is split into upper and lower part by an elastic partition known as basilar membrane that runs from starting to the ending of the cochlea. This basilar membrane functions as the foundation that supports the vital hearing structures.

After these vibrations ripple the fluid within the cochlea, there is a formation of wave that travels along the basilar membrane; sensory cells and hair cells reside atop the basilar membrane and move like a wave too.

The hair cells move in a wave like motion and the stereocilia, which are the microscopic hair-like projections present on the top of the hair cells slam against another structure overhead and bend. This bending results in opening up of minute channels present on the stereocilia. This results in rushing of chemicals into the cell leading in formation of electrical signal. This electrical signal is carried by the auditory nerves to the brain, which transforms this signal into a sound/noise which we understand and recognize.

Now this was the normal hearing process that occurs in our body. Majority of the noise-induced hearing loss is caused by the damage and the destruction of these important hair cells within our ears.(3) Human hair cells do not grow back. Once they are dead, they cannot regenerate; hence the hearing loss is permanent.

What are the Causes of Noise-Induced Hearing Loss NIHL ?

Noise-Induced Hearing Loss can be caused by a single-time exposure to extremely loud sound (impulse noise), like from an explosion; or NIHL can also be caused from persistent exposure to extremely loud sounds over a prolonged length of time(2), e.g. noise produced from woodworking shop.

There are some recreational activities also that can increase your risk for developing noise-induced hearing loss such as: hunting, shooting, riding a snowmobile, listening to music at high volume via headphones/ear buds or attending loud shows/concerts.(7)

Other causes of noise-induced hearing loss consist of extremely loud volumes of sound, such as explosions or gunshots that can cause rupture or damage to the eardrum or cause damage to the middle ear bones.(8) This type of noise-induced hearing loss is often immediate and can be permanent.(8)

In the household arena, harmful noises that can lead to noise-induced hearing loss consist of leaf blowers, lawnmowers and woodworking tools.(8)

What Factors Play a Role in Noise-Induced Hearing Loss ?(2)

The distance of source of the loud sound and the duration of the time you are exposed to any sound are very important factors in causing noise-induced hearing loss and should be taken into consideration when thinking about protecting your hearing and preventing noise-induced hearing loss.(8) A safe guideline for this, and to prevent noise-induced hearing loss, is to avoid exposure to noises that are very close, very loud or last for a long time.

How Soon Does One Develop Noise-Induced Hearing Loss ?(8)

Noise-induced hearing loss can either take time to develop or can be felt instantly. NIHL can be permanent or temporary; it can affect both ears or only one ear. Like said before, the patient may not immediately experience this hearing loss, but noise-induced hearing loss can develop gradually where you can have difficulty in your hearing in future, like not able to hear when others are talking; especially in a noisy room or on the phone. However, have no fear, as noise-induced hearing loss is very much preventable.

What are the Signs and Symptoms of Noise-Induced Hearing Loss (NIHL) ?(8)

When a person is exposed to a loud noise for extended length of time, then the patient can gradually lose hearing. The damage to hearing from the noise exposure is often slow and the patient may not even observe it and can ignore the indications of hearing loss until it becomes more pronounced. After some time, the sounds can feel muffled or distorted and there is difficulty in understanding what others are talking. Sometimes, when suffering from gradual development of noise-induced hearing loss you may even need to tell other people to repeat what they have said or speak more loudly. You may also have to increase the volume of your television to be able to listen clearly.

In elderly people, hearing damage caused by NIHL, along with the aging process can lead to extreme hearing loss where hearing aids are needed to amplify the sounds around you, so you can hear clearly and participate and communicate better in day to day activities.

Other symptoms from exposure to loud noise include tinnitus, which is a buzzing, ringing or roaring type of sound in the ears or head.(1) This condition can subside over a time, however, can also persist constantly or occasionally throughout the patient’s life. Tinnitus and hearing loss can occur in one or both the ears.

In some cases, exposure to continuous or impulse loud noise can result in a temporary hearing loss that can subside about 16 to 48 hours later. According to recent studies, even if the loss of hearing seems to subside, there can be lingering long-term damage to the hearing.

What is the Treatment for Noise-Induced Hearing Loss ?(8)

As of now, noise-induced hearing loss has no cure.(6)

For treatment, if you suspect that you or any other person is suffering from hearing loss, then immediately consult otolaryngologist or otologist, who is a physician with specialized training in ear and hearing disorders. The doctor can diagnose your hearing problems and is the best person to recommend ways to manage your hearing loss.

Research on Treatment for Noise-Induced Hearing Loss

As of now, research is going on for the potential of antioxidants in order to prevent hearing loss and restore hearing.(1) According to this research, vitamin E and aspirin can help reduce hearing loss if they are used before exposure to loud sound/noise.

In animal studies, the use of Vitamins A, C, E and magnesium when used before exposure to loud noise can also prevent hearing loss. Trial in humans is in progress.

How Can You Prevent Noise-Induced Hearing Loss ? (8)

Noise-induced hearing loss is the only type of hearing loss, which is absolutely preventable. A person needs to understand the hazards of noise pollution and loud sounds and learn to practice good hearing health so that he/she can have proper hearing for life.

The measures that need to be undertaken to prevent noise-induced hearing loss are:

  • Always wear protective devices, such as earplugs or when you are exposed to loud noises or are involved in loud activities.(6) You also need to protect the ears of children who are too young to protect on their own.
  • Understand the type of sound/ noises that can cause hearing damage i.e. sounds above 85 dBA.(4)
  • If you are unable to protect yourself from the noise or cannot turn down the noise, then just walk away from it.
  • Always be on alert to loud and harmful sounds present in the environment.
  • Also, try to educate your friends, family and colleagues aware about hazards of loud noises and about good hearing health.(5)
  • If you suspect that you are suffering from hearing loss then, consult your physician and get your hearing tested.

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