Noise-induced hearing loss (NIHL)

Noise is a common cause of hearing loss in adults. During our lives, the cumulative effects of noisy workplaces, busy city streets, technology exposure, loud recreational events and hobbies take a toll on the delicate structures of the inner ear resulting in permanent sensorineural hearing loss. It's happening to people at younger ages due in part to listening to music at damaging volumes with the use of headphones. It is estimated that at least 26 million Americans have hearing loss due to noise exposure.

What is noise?

Sound is what we hear when vibrations from the source travel through the air and reach our ears. Noise is sometimes defined as unwanted sound, but in terms of hearing health, the definition is much broader. Noise is the sound around us, whether it is the ear-splitting guitar riff at a live concert, the boom of a fireworks display finale, the loud crack of a hunting rifle, the roar of the lawnmower or the piped in music at a hip new restaurant at happy hour. 

Mechanisms of NIHL

To understand how noise-induced hearing loss works, it's first important to know how hearing works. Sound waves enter the outer ear and travel through the ear canal. The waves reach the eardrum which sends vibrations to the three middle ear bones (ossicles) called the malleus, incus and stapes, or the hammer, anvil and stirrup, respectively. These bones amplify and transmit the sounds via vibrations to the fluid in the cochlea. The fluids of the cochlea bend the receptors of tiny hair cells, triggering electrical signals in the auditory nerve, which travel to the brain. The brain translates these signals into the sounds we perceive and understand.

In the presence of sounds that are too loud, the vibrations get larger, causing fluid motion in the cochlea that can bend the hair cells to the point of breaking. Hair cells are not replaceable structures. Damaged hair cells are unable to trigger electrical signals to the brain, impeding hearing. Both intense but short noises - such as a nearby gunshot -  and repeated or continuous exposure to loud noises - such as operating construction equipment - can damage the hair cells. 

Causes of NIHL

Occupational exposure

For some Americans, the workplace is the most common origin of NIHL. Jobs with the highest risk of noise exposure include:

• Agriculture: Tractors, combines, grain dryers, crop-dusting aircraft and orchard sprayers can register between 80 and 115 decibels (dB). Even pig squeals are dangerous, measuring between 85 and 115 dB!
• Construction and carpentry: According to the Center for Disease and Control (CDC), 44 percent of carpenters and 48 percent of plumbers report being hard of hearing.
• Mining: According to the CDC, nearly 50 percent of miners will have hearing loss by age 50, compared to only 9 percent of the general population. Additionally, 70 percent of miners will have hearing loss by age 60.
• Military: According to recent news reports, NIHL is the most common injury of returning war veterans in the U.S. due to combat, bombs and artillery fire. According to a 2009 news report by The Guardian, 69 percent - or more than two-thirds - of Royal Marine commandos returning from war in Afghanistan were affected by NIHL.

The Occupational Safety and Health Administration (OSHA) requires employers to take precautions to limit employees' hazardous noise exposure, including providing hearing protection equipment, maintaining machinery, placing barriers or isolating the noise source and developing a hearing conservation program to test employees' hearing. You can find the OSHA regulations online. If you are provided hearing protection at your place of employment, take it seriously. Noise-induced hearing loss can be prevented!

Recreational exposure

There are things we do for fun that can also cause NIHL, including snowmobiling, shooting at a firing range, hunting, attending concerts, listening to extremely loud music and riding motorcycles.

Audiologists conducted a sound test of 33 motorcycles at the University of Florida and found that more than half produced noise above 100 dB when throttled. This level of noise exposure is only safe for up to 15 minutes, according to OSHA. Surprisingly, even more dangerous to hearing however, is the use of helmets; wind noise is constant, and it rushes around the helmet, creating pressure variations. At only 55 miles per hour, the wind noise a motorcyclist is exposed to can reach 90 dB. However, traveling between 75 and 80 miles per hour, wind noise is around 105 dB. Helmets are a must for safety reasons, so motorcyclists should also protect their ears by wearing earplugs.

Attending loud concerts, being a professional musician and listening to music at loud levels are all possible sources of NIHL. A study from the Netherlands showed that 50 percent of adolescents using earphones used high-volume settings, and only 7 percent had a noise-limiting device.

Diagnosis

Here are some symptoms that should encourage you to get your hearing tested by a hearing care professional:

• You have trouble understanding what other people are saying, or it sounds like they are mumbling. 
• You have pain in your ears following loud noise exposure.
• Other people comment that you're talking loudly or shouting.
• You have tinnitus - ringing, whooshing, roaring or buzzing sounds in your ears - after noise exposure.

Other effects of loud noise exposure

Aside from damaging the hearing, loud noise exposure and NIHL can lead to:

• Stress
• Anxiety
• Insomnia, even after noise stops
• High blood pressure
• Increased heart rate
• Isolation due to hearing loss
• Depression due to hearing loss

Precautions

Noise-induced hearing loss is usually permanent, so it's important to take precautions to protect your ears. There are several solutions available for people who anticipate being in loud noise situations, including:

• Disposable earplugs, which are placed in the ear canal to totally block it, can be purchased at drug, hardware and sporting goods stores. They come in different sizes and lower noise levels by 15 to 30 decibels, which is beneficial in most situations, but not all. Earplugs can also be custom-molded to fit your ears by a hearing healthcare professional. 
• Earmuffs, which fit completely over the ears and form a seal, lower noise levels by 15 to 30 dB. You can pair earmuffs and plugs together for better noise reduction.
• Replacing loud machine parts and using lubricant can reduce friction and lower noise. Many cars, farm equipment and other machinery have mufflers, silencers and bearings that can lessen sound.
• Turning music down can preserve your hearing. Earbuds inserted directly into the ear canals put loud music right at the eardrum. Be conscious of how loud your music is, and never use music to block out other unwanted sound.
• Be mindful. Once you become aware of noise hazards, you will notice them everywhere and can take action. For example, avoid walking directly by active construction sites and cross the street instead. If you're stuck in traffic on a busy highway, roll up your car windows for a quieter ride. Wear inexpensive foam earplugs while mowing the lawn or operating a leaf blower. 

Treatment for NIHL

Noise-induced hearing loss is, unfortunately, permanent. While researchers sometimes stumble upon potential treatments that could one day restore the function of healthy ears, these solutions are not likely to come soon enough for the millions of Americans who need help now.

For them, and maybe for you, the best treatment for NIHL is properly fitted hearing aids. Today's technology works, and solutions are widely available for every budget and lifestyle need. If you already have hearing loss, visit a hearing healthcare professional like one listed in our directory of consumer-reviewed clinics and make an appointment today. 

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