Understanding Noise-Induced Hearing Loss

Noise-induced hearing loss (NIHL) is any hearing loss that is caused by exposure to loud sound. Simple, right? It’s a little more complicated than it sounds at first, but a better understanding of NIHL can help us to better guard against it and maintain better hearing health for more of our lives.

Types of NIHL

A massive sonic event can rupture the eardrums and even cause damage to the bones in the middle ear. While still technically NIHL, this is very different from the type of hearing loss we normally associate with exposure to loud sounds like factories or rock & roll music.

The typical type of NIHL we think of is a type of sensorineural hearing loss, meaning that it results from damage to or destruction of the cilia (tiny, hair-like cells) inside the cochlea, in the inner ear. These cilia are the cells that convert different frequencies of sound into electrical impulses to be sent to the brain. There are a number of ways they can become damaged, and loud sound is a common one. In fact, it’s estimated that up to 20% of teenagers have some amount of NIHL in one or both ears.

The cilia have to be extremely sensitive to perform their duty, but this also means they can easily be damaged. While our ears are perfectly tuned for the kinds of activities early humans would have undertaken, they’re not capable of handling the kinds of loud sounds we’ve “invented,” like massive diesel engines, PA systems, or earbuds at full volume.

How Much Sound Is Too Much?

Sometimes one activity, like attending a rock concert without earplugs, can leave our ears ringing for days afterward. It’s likely that we’ve lost some hearing in the course of that activity, but did you know it takes much less than the volume levels you encounter at a rock concert to cause NIHL?

Sound is measured in decibels. Depending on the type of sound, one type of weighting might be more appropriate than another, but for general measurements of environmental sound, “decibels A-weighted” (dBA) is the standard.

The rock concert likely reached levels of around 110 dBA. For additional reference, a movie theater can reach up to 104 dBA, a loud motorcycle can reach 110 dBA for a person sitting on it, sirens range from around 110–130 dBA, and a normal conversation with one other person will range from 60–70 dBA.

It’s not as though there is a particular threshold at which NIHL will absolutely occur. Too many factors are at play. (One Japanese study found that factory workers who used the same machines for the same amounts of time had more hearing loss if they smoked cigarettes while they worked.)

As a general rule, NIHL will set in after about 8 hours of exposure to 80 dBA. For every additional 3 dBA, the time before NIHL occurs is cut in half. So in an environment where the sound averages 95 dBA, it takes about 15 minutes of exposure for permanent hearing loss to occur. At 110 dBA, less than 1 minute of exposure can cause permanent hearing loss.

Protection Is Crucial

Sensorineural hearing loss is permanent. While genetic treatments are being explored that could one day potentially cure hearing loss, even the scientists who are studying those treatments will admit that it is a long way off. The best practice is to wear earplugs whenever you are exposed to loud sound.

Smartphone apps are available that can measure the decibel level of environmental sound. If you’re unsure of whether an environment is potentially hazardous, you can open up the app and check. If the sound measures 80 dBA or above, it’s a good idea to wear earplugs, especially if you expect to be exposed for more than a few minutes.

Get Regular Hearing Tests

If you’re having trouble hearing and think you might have NIHL, make an appointment for a hearing test today and find out. Even if your hearing loss is not at the level that might require hearing aids, it’s a good idea to start keeping track of your hearing health. By getting periodic hearing tests, you can be sure that whatever measures you’re taking to prevent hearing loss are working. If they aren’t, you can change something before it’s too late.

The Better Hearing Institute, a non-profit organization, recommends getting a hearing test once every decade until age 50, and once every 3 years after that. Preventing hearing loss is the best course of action.

If a hearing loss is detected, the most common treatment is the use of hearing aids. It is best to seek treatment as soon as you notice changes in your hearing. With untreated hearing loss, complications can arise, and an ever-growing body of scientific literature is making it clear that hearing loss can set off a cascade of negative health effects if it is left untreated. Make an appointment for a hearing test today, and keep your ears and the rest of your body in good shape!