Hearing loss that occurs gradually as you age (presbycusis) is common.
Hearing loss is defined as one of three types:
- Conductive (involves outer or middle ear)
- Sensorineural (involves inner ear)
- Mixed (combination of the two)
Aging and chronic exposure to loud noises both contribute to hearing loss. Other factors, such as excessive earwax, can temporarily reduce how well your ears conduct sounds.
You can’t reverse most types of hearing loss. However, you and your doctor or a hearing specialist can take steps to improve what you hear.
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 (malleus), the anvil (incus) and the stirrup (stapes). These bones are separated from the outer ear by the eardrum (tympanic membrane), which vibrates when struck by a sound wave.
- 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. This is where the initial damage and hearing loss occur due to age, noise exposure or medication.
- 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 fluid 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
- 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
Causes
To understand how hearing loss occurs, it can be helpful to first understand how you hear.
How you hear
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. Your brain turns these signals into sound.
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.
- Gradual buildup of earwax. Earwax can block the ear canal and prevent conduction of sound waves. Earwax removal can help restore your hearing.
- 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 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, carpentry or listening to loud music.
- Some medications. Drugs such as the antibiotic gentamicin, sildenafil (Viagra) 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
The chart below lists common sounds and their decibel levels. The Environmental Protection Agency’s (EPA) safe noise level is 70 decibels. The louder the noise, the less time it takes to cause permanent hearing damage.
| Sound levels of common noises | |
|---|---|
| Decibels | Noise source |
| Safe range | |
| 30 | Whisper |
| 40 | Refrigerator |
| 60 | Normal conversation |
| 75 | Dishwasher |
| Risk range | |
| 85 | Heavy city traffic, school cafeteria |
| 95 | Motorcycle |
| 100 | Snowmobile |
| 110 | Chain saw, jackhammer, rock concert, symphony |
| 115 | Sandblasting |
| 120 | Ambulance siren, thunder |
| 140-165 | Firecracker, firearms |
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 |
| 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 |
Complications
Hearing loss can have a significant effect on your quality of life. Older adults with hearing loss may report feelings of depression. Because hearing loss can make conversation difficult, some people experience feelings of isolation. Hearing loss is also associated with cognitive impairment and decline.
The mechanism of interaction between hearing loss, cognitive impairment, depression and isolation is being actively studied. Initial research suggests that treating hearing loss can have a positive effect on cognitive performance, especially memory.
Prevention
The following steps can help you prevent noise-induced hearing loss and avoid worsening of age-related hearing loss:
- Protect your ears. Limiting the duration and intensity of your exposure to noise is the best protection. In the workplace, plastic earplugs or glycerin-filled earmuffs can help protect your ears from damaging noise.
- Have your hearing tested. Consider regular hearing tests if you work in a noisy environment. If you’ve lost some hearing, you can take steps to prevent further loss.
- Avoid recreational risks. Activities such as riding a snowmobile, hunting, using power tools or listening to rock concerts can damage your hearing over time. Wearing hearing protectors or taking breaks from the noise can protect your ears. Turning down the music volume is helpful too.
Diagnosis
Tests to diagnose hearing loss may include:
- Physical exam. Your doctor will look in your ear for possible causes of your hearing loss, such as earwax or inflammation from an infection. Your doctor will also look for any structural causes of your hearing problems.
- General screening tests. Your doctor may use the whisper test, asking you to cover one ear at a time to see how well you hear words spoken at various volumes and how you respond to other sounds. Its accuracy can be limited.
- App-based hearing tests. Mobile apps are available that you can use by yourself on your tablet to screen for moderate hearing loss.
- Tuning fork tests. Tuning forks are two-pronged, metal instruments that produce sounds when struck. Simple tests with tuning forks can help your doctor detect hearing loss. This evaluation may also reveal where in your ear the damage has occurred.
- Audiometer tests. During these more-thorough tests conducted by an audiologist, you wear earphones and hear sounds and words directed to each ear. Each tone is repeated at faint levels to find the quietest sound you can hear.
Treatment
If you have hearing problems, help is available. Treatment depends on the cause and severity of your hearing loss.
Options include:
- Removing wax blockage. Earwax blockage is a reversible cause of hearing loss. Your doctor may remove earwax using suction or a small tool with a loop on the end.
- Surgical procedures. Some types of hearing loss can be treated with surgery, including abnormalities of the eardrum or bones of hearing (ossicles). If you’ve had repeated infections with persistent fluid, your doctor may insert small tubes that help your ears drain.
- Hearing aids. If your hearing loss is due to damage to your inner ear, a hearing aid can be helpful. An audiologist can discuss with you the potential benefits of a hearing aid and fit you with a device. Open fit aids are currently the most popular, due to fit and features offered.
- Cochlear implants. If you have more severe hearing loss and gain limited benefit from conventional hearing aids, then a cochlear implant may be an option. Unlike a hearing aid that amplifies sound and directs it into your ear canal, a cochlear implant bypasses damaged or nonworking parts of your inner ear and directly stimulates the hearing nerve. An audiologist, along with a medical doctor who specializes in disorders of the ears, nose and throat (ENT), can discuss the risks and benefits.
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