Overview
Hearing loss that occurs gradually as you age (presbycusis) is common. Almost half the people in the United States older than age 65 have some degree of hearing loss.
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.
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.
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Book: Mayo Clinic on Hearing and Balance
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
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. Age-related hearing loss occurs gradually, so you may not notice it at first.
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.
omparing 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.
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.
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