Signs and symptoms of hearing loss may include:

• Muffled quality of speech and other sounds
• Difficulty understanding words, especially against background noise or in a crowd of people
• 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?
Talk to your doctor if you have difficulty hearing. 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; if sounds seem muffled; or if you find yourself having to turn the volume higher when you listen to music, the radio or television.

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: the 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 — the hammer, anvil and stirrup — amplify the vibrations as they travel to the inner ear. There, the vibrations pass through fluid in the cochlea, a snail-shaped structure in the inner ear.
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.

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.
Ear infection and abnormal bone growths or tumors of the outer or middle ear can cause hearing loss. A ruptured eardrum also may result in loss of hearing.

Risk factors to hearing loss
Factors that may damage or lead to loss of the hairs and nerve cells in your inner ear include:

• Aging. Exposure to sounds over the years can damage the cells of your inner ear.
• Heredity. Your genetic makeup may make you more susceptible to ear damage.

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 fireworks, can cause immediate, permanent hearing loss. Other recreational activities with dangerously high noise levels include snowmobiling, motorcycling or listening to loud music. Personal music players such as MP3 players can cause lasting hearing loss if you turn the volume up high enough to mask the sound of other loud noises, such as a lawn mower.

• 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 or nonsteroidal anti-inflammatory drugs (NSAIDs), 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:

Adapted from National Institute on Deafness and Other Communication Disorders, 2008, the National Institute for Occupational Safety and Health, 2009, and American Tinnitus Association, 2009
Maximum sound-exposure durations
Below are the maximum noise levels on the job to which you should be exposed without hearing protection, and for how long.

Source: Department of Labor's Occupational Safety & Health Administration, 2005 - All under http://www.mayoclinic.com/health/