Overview
Hearing loss that occurs gradually as you age (presbycusis) is common. About 25 percent of people in the United States between the ages of 55 and 64 have some degree of hearing loss. For those older than 65, the number of people with some hearing loss is almost 1 in 2.
Aging and chronic exposure to loud noises are significant factors that contribute to hearing loss. Other factors, such as excessive earwax, can temporarily prevent your ears from conducting sounds as well as they should.
You can't reverse most types of hearing loss. However, you don't have to live in a world of muted, less distinct sounds. You and your doctor or a hearing specialist can take steps to improve what you hear.
Parts of the ear
The ear is made up of three primary parts: the outer ear, middle ear and inner ear. Each section is composed of structures that play distinct roles in the process of converting sound waves into signals that go to the brain.
Outer ear
The outer ear is composed of the visible part of the ear (pinna) and the ear canal. The cup-shaped pinna (PIN-uh) gathers sound waves from the environment and directs them into the ear canal.
Middle ear
The middle ear is an air-filled cavity that holds a chain of three bones: the hammer, anvil and stirrup. These bones are separated from the outer ear by the eardrum (tympanic membrane), which when struck by a sound wave, vibrates.
The middle ear is connected to the back of your nose and upper part of your throat by a narrow channel called the auditory tube (eustachian tube). The tube opens and closes at the throat end to equalize the pressure in the middle ear with that of the environment and drain fluids. Equal pressure on both sides of the eardrum is important for normal vibration of the eardrum.
Bones of the middle ear
The middle ear contains three tiny bones:
- Hammer (malleus) — attached to eardrum
- Anvil (incus) — in the middle of the chain of bones
- Stirrup (stapes) — attached to the membrane-covered opening that connects the middle ear with the inner ear (oval window)
The vibration of the eardrum triggers a chain of vibrations through the bones. Because of differences in the size, shape and position of the three bones, the force of the vibration increases by the time it reaches the inner ear. This increase in force is necessary to transfer the energy of the sound wave to the fluid of the inner ear.
Inner ear
The inner ear contains a group of interconnected, fluid-filled chambers. The snail-shaped chamber, called the cochlea (KOK-lee-uh), plays a role in hearing. Sound vibrations from the bones of the middle ear are transferred to the fluids of the cochlea. Tiny sensors (hair cells) lining the cochlea convert the vibrations into electrical impulses that are transmitted along the auditory nerve to your brain.
The other fluid-filled chambers of the inner ear include three tubes called the semicircular canals (vestibular labyrinth). Hair cells in the semicircular canals detect the motion of the fluids when you move in any direction. They convert the motion into electrical signals that are transmitted along the vestibular nerve to the brain. This sensory information enables you to maintain your sense of balance.
Traveling to the brain
Electrical impulses travel along the auditory nerve and pass through several information-processing centers. Signals from the right ear travel to the auditory cortex located in the temporal lobe on the left side of the brain. Signals from the left ear travel to the right auditory cortex.
The auditory cortices sort, process, interpret and file information about the sound. The comparison and analysis of all the signals that reach the brain enable you to detect certain sounds and suppress other sounds as background noise.
Symptoms
Signs and symptoms of hearing loss may include:
- Muffling of speech and other sounds
- Difficulty understanding words, especially against background noise or in a crowd of people
- Trouble hearing consonants
- Frequently asking others to speak more slowly, clearly and loudly
- Needing to turn up the volume of the television or radio
- Withdrawal from conversations
- Avoidance of some social settings
When to see a doctor
If you have a sudden loss of hearing, particularly in one ear, seek immediate medical attention.
Talk to your doctor if difficulty hearing is interfering with your daily life. Your hearing may have deteriorated if:
- You find that it's harder to understand everything that's said in conversation, especially when there's background noise
- Sounds seem muffled
- You find yourself having to turn the volume higher when you listen to music, the radio or television
Causes
Some causes of hearing loss include damage to the inner ear, a buildup of earwax, infections and a ruptured eardrum. To understand how hearing loss occurs, it can be helpful to understand how you hear.
How you hear
Hearing occurs when sound waves reach the structures inside your ear, where the sound wave vibrations are converted into nerve signals that your brain recognizes as sound.
Your ear consists of three major areas: outer ear, middle ear and inner ear. Sound waves pass through the outer ear and cause vibrations at the eardrum. The eardrum and three small bones of the middle ear amplify the vibrations as they travel to the inner ear. There, the vibrations pass through fluid in a snail-shaped structure in the inner ear (cochlea).
Attached to nerve cells in the cochlea are thousands of tiny hairs that help translate sound vibrations into electrical signals that are transmitted to your brain. The vibrations of different sounds affect these tiny hairs in different ways, causing the nerve cells to send different signals to your brain. That's how you distinguish one sound from another.
How hearing loss can occur
Causes of hearing loss include:
-
Damage to the inner ear. Aging and exposure to loud noise may cause wear and tear on the hairs or nerve cells in the cochlea that send sound signals to the brain. When these hairs or nerve cells are damaged or missing, electrical signals aren't transmitted as efficiently, and hearing loss occurs. Higher pitched tones may become muffled to you.
It may become difficult for you to pick out words against background noise. Heredity may make you more prone to these changes. This type of hearing loss is known as sensorineural hearing loss, which is permanent.
- A gradual buildup of earwax. Earwax can block the ear canal and prevent conduction of sound waves. This can be restored with earwax removal.
- Ear infection and abnormal bone growths or tumors. In the outer or middle ear, any of these can cause hearing loss.
- Ruptured eardrum (tympanic membrane perforation). Loud blasts of noise, sudden changes in pressure, poking your eardrum with an object and infection can cause your eardrum to rupture and affect your hearing.
Risk factors
Factors that may damage or lead to loss of the hairs and nerve cells in your inner ear include:
- Aging. Degeneration of delicate inner ear structures occurs over time.
- Loud noise. Exposure to loud sounds can damage the cells of your inner ear. Damage can occur with long-term exposure to loud noises, or from a short blast of noise, such as from a gunshot.
- Heredity. Your genetic makeup may make you more susceptible to ear damage from sound or deterioration from aging.
- Occupational noises. Jobs where loud noise is a regular part of the working environment, such as farming, construction or factory work, can lead to damage inside your ear.
- Recreational noises. Exposure to explosive noises, such as from firearms and jet engines, can cause immediate, permanent hearing loss. Other recreational activities with dangerously high noise levels include snowmobiling, motorcycling or listening to loud music.
- Some medications. Drugs, such as the antibiotic gentamicin and certain chemotherapy drugs, can damage the inner ear. Temporary effects on your hearing — ringing in the ear (tinnitus) or hearing loss — can occur if you take very high doses of aspirin, other pain relievers, antimalarial drugs or loop diuretics.
- Some illnesses. Diseases or illnesses that result in high fever, such as meningitis, may damage the cochlea
Comparing loudness of common sounds
What kind of decibel levels are you exposed to during a typical day? To give you an idea, compare noises around you to these specific sounds and their corresponding decibel levels:
| Sound levels of common noises |
| Decibels |
Noise source |
| BASED ON THE NATIONAL INSTITUTE ON DEAFNESS AND OTHER COMMUNICATION DISORDERS, 2010, AND THE NATIONAL INSTITUTE FOR OCCUPATIONAL SAFETY AND HEALTH, 2013 |
|
Safe range |
| 30 |
Whisper |
| 60 |
Normal conversation |
| 78 |
Washing machine |
|
Risk range |
| 80 to 90 |
Heavy city traffic, power lawn mower |
| 90 |
Motorcycle |
| 100 |
Snowmobile, hand drill |
| 110 |
Chain saw, rock concert |
|
Injury range |
| 120 |
Ambulance siren |
| 140 (pain threshold) |
Jet engine at takeoff |
| 165 |
12-guage shotgun blast |
| 180 |
Rocket launch |
Maximum sound-exposure durations
Below are the maximum noise levels on the job to which you may be exposed without hearing protection, and for how long.
| Maximum job-noise exposure allowed by law |
| Sound level, decibels |
Duration, daily |
| BASED ON OCCUPATIONAL SAFETY & HEALTH ADMINISTRATION, 2008 |
| 90 |
8 hours |
| 92 |
6 hours |
| 95 |
4 hours |
| 97 |
3 hours |
| 100 |
2 hours |
| 102 |
1.5 hours |
| 105 |
1 hour |
| 110 |
30 minutes |
| 115 |
15 minutes or less |
Complications
Hearing loss can have a significant effect on your quality of life. Among older adults with hearing loss, commonly reported problems include:
- Depression
- Anxiety
- An often false sense that others are angry with you
Unfortunately, most people affected by hearing loss live with these difficulties for years before seeking treatment — or never seek treatment at all. This may also cause lasting problems for those who love you, if you try to cope by denying your hearing loss or withdrawing from social interactions.
Prevention
Hearing loss prevention consists of steps you can take to help you prevent noise-induced hearing loss and avoid worsening of age-related hearing loss:
- Protect your ears in the workplace. Specially designed earmuffs that resemble earphones can protect your ears by bringing most loud sounds down to an acceptable level. Foam, pre-formed or custom-molded earplugs made of plastic or rubber also can help protect your ears from damaging noise.
- Have your hearing tested. Consider regular hearing tests if you work in a noisy environment. Regular testing of your hearing can provide early detection of hearing loss. Knowing you've lost some hearing means you're in a position to take steps to prevent further hearing loss.
- Avoid recreational risks. Some activities, such as riding a snowmobile, hunting or listening to rock concerts for long periods of time, can damage your hearing. Wearing hearing protectors or taking breaks from the noise during loud recreational activities can protect your ears. Turning down the volume when listening to music can help you avoid damage to your hearing.
Sept. 03, 2015