Noise-induced hearing loss (NIHL)

Exposure to hazardous noise is a common cause of hearing loss in adults. During our lives, the cumulative effects of noisy environments, also known as noise pollution, take a toll on the delicate structures of the inner ear. This can result in permanent sensorineural hearing loss.

While adults are at highest risk of noise-induced hearing loss, the rapid increase in headphone and earbud use among kids and teens means they're at risk, too.

Sound vs. 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, whether it is ear-splitting feedback from an amplifier at a live concert, the boom of a fireworks display finale, the loud crack of gunfire, the roar of the lawnmower, or the piped in music and loud clamor of voices at a hip new restaurant.

In fact, our world has gotten so noisy that "noise pollution" is now considered a public health threat.

What is noise-induced hearing loss (NIHL)? 

In simple terms, noise-induced hearing loss is permanent damage to the tiny hair cells in your ears, known as stereocilia, from loud sounds. Akin to earthquakes, hazardous levels of noise produce vibrations in the hair cells that are so powerful they are damaging—sometimes permanently.

Hair cells are not replaceable and do not regrow. 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. 

Symptoms of noise-induced hearing loss 

Noise-induced hearing loss typically makes it harder to hear high-frequency sounds, which is easy to detect with a hearing test that can be charted on an audiogram. It will show a dip to the right, known as a noise-notch pattern.

Day to day, a person may struggle to hear speech, especially words with "s," "f," "sh" and "th" sounds in them. (For example, the words "shell" "sell" and "fell" are hard to distinguish.) You can hear, yet have trouble understanding what other people are saying, even if they're raising their voice.

Other signs that you need to get your hearing tested by a hearing care professional include:

• 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.
• You may experience diplacusis, or "double hearing," though this is rare.

Noise levels of common sounds

In general, people are advised against exposure to any sound above about 85 decibels, though it also depends on how long and how often a person is exposed, as well as how close they are to the sound. A hair stylist using a hair dryer at 70 dB all day can still develop hearing loss, for example, because of how long, how close and how often they are exposed. But a person only periodically using a vacuum cleaner, which is usually around 70 decibels, is at much lower risk because of the short, infrequent duration of noise exposure.

Common causes of noise-induced hearing loss

Workplace exposure

A staggering 1 out of every 4 American workers have been repeatedly exposed to dangerous noise, according to the Center for Disease Control and Prevention's National Institute for Occupational Safety and Health, and about 12% of all workers have hearing difficulty. Eight percent have tinnitus (which can result from noise exposure). CDC data shows that jobs with the highest risk include:

• Mining and oil and gas extraction
• Agriculture
• Construction and carpentry
• Military: The VA provides hearing aids for veterans who qualify.

The Occupational Safety and Health Administration (OSHA) requires employers to have hearing conservation programs 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. Read more about OSHA hearing regulations here. If you are provided hearing protection at your place of employment, take it seriously. Noise-induced hearing loss can be prevented. You also may be entitled to workers' compensation benefits for on-the-job hearing loss.

More: Hearing loss in the workplace

Is your hobby harming your hearing?

Things we do for fun can also cause NIHL, including hunting or shooting at a firing range, attending concerts, listening to loud music (or performing it), operating lawn and home improvement equipment, and riding motorcycles and snowmobiles.

Other harmful effects of loud noise exposure

Aside from damaging your hearing, research shows that noise pollution and NIHL can lead to:

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

Fortunately, research shows that hearing aids help with many of these health problems.

How many people have noise-induced hearing loss?

Statistics show about 40 million US adults aged 20-69 years have noise-induced hearing loss.

How to prevent noise-induced hearing loss

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 foam earplugs, which are placed in the ear canal, 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 the sound.
• Turning music down. 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 sounds. More on how to prevent hearing loss from headphones or earbuds.
• 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. 

How do I know if something is too loud?

How loud is too loud? Your can find out via your phone and our list of the best smartphone decibel meter apps to measure sound levels. In general, though, you know it's too loud if you have to lean in close to talk to someone next to you, or shout at them. If you leave the event, and your hearing is muffled, you have experienced temporary threshold shift.

How do you treat noise-induced hearing loss?

Noise-induced hearing loss is, unfortunately, permanent. Typically the best treatment for NIHL is properly fitted hearing aids. Today's technology works better than hearing aids of decades ago, and solutions are widely available for every budget and lifestyle need.

If you already have hearing loss, find a hearing care provider near you and make an appointment.