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

To understand how hearing loss occurs, it can be helpful to first understand 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.

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.

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.