context: For 37 million Americans, the world is a very quiet place. Severe hearing loss can make conversations fade into whispers and turn music into a faint hum. See your doctor as soon as you have trouble hearing. The earlier you get a diagnosis and treatment, the more you can stay involved in the world around you. If you lose hearing, either suddenly or over time, details of conversations may become fuzzy. Sounds will become muffled and gradually fade. Depending on the cause of your hearing loss, you may also have: Pain in one or both ears Dizziness or vertigo Ringing in the ears, called tinnitus Pressure or fullness in one or both ears Often, people with severe hearing loss withdraw from their social lives because they're embarrassed to ask family and friends to repeat themselves over and over again. They might be afraid they'll misunderstand a conversation and answer with the wrong comments. To find out how impaired your hearing is, your doctor may order a formal hearing test also known as an audiogram. It can show the degree of your hearing loss by looking at the range of decibels -- a measure of loudness -- you can hear. Normal hearing is in the range of 0 to 20 decibels. People with normal hearing are able to make out sounds as faint as human breathing, which measures about 10 decibels. Mild hearing loss ranges from 21 to 40 decibels. Moderate hearing loss ranges from 41 to 55 decibels. Moderately severe hearing loss ranges from 56 to 70 decibels. Severe hearing loss is in the range of 71 to 90 decibels. Profound hearing loss is greater than 90 decibels. People with severe to profound hearing loss will have trouble hearing speech, although they can make out loud sounds like a truck that backfires or an airplane taking off. There are three main types of hearing loss: Conductive hearing loss happens because of a problem in the ear canal, eardrum, or the middle ear that prevents sound from carrying well to the inner ear. An ear infection, trauma, a tumor, or fluid or an object in the ear (such as wax buildup) can cause it. Sensorineural hearing loss happens most often from damage to the hair cells in the inner ear. Other causes include damage to the nerve for hearing, called the auditory nerve, or the brain. It's usually happens as you get older, but it also can happen because of noise exposure, chemotherapy, radiation, trauma, and your genes. Mixed hearing loss is a combination of conductive and sensorineural hearing loss. There may be a problem in the outer or middle ear and in the inner ear or auditory nerve. It can happen after a head injury, long-term infection, or because of a disorder that runs in your family. Hearing loss can affect one or both ears. It can happen suddenly or gradually get worse over time. If you notice sudden hearing loss, you should see an ear, nose, and throat specialist as soon as possible. When your hearing is normal, sound waves enter your outer ear and cause your eardrum and middle ear bones to vibrate. The sound waves then travel through your inner ear, which is a shell-shaped, fluid-filled tube called the cochlea. As the fluid moves, it sets in motion thousands of tiny hairs that convert the sound vibrations into nerve signals. Those signals go to your brain where they are turned into sounds you can recognize. Hearing loss happens when there's a problem with the parts of the ear that you use to hear. Any of these conditions can lead to severe hearing loss: Age. As people get older, some parts in the ear become less elastic. The tiny hairs get damaged and can't respond to sound waves as well. Hearing loss can get worse over several years. Loud noise. The blare of power tools, airplanes, or loud music on headphones, for example, can damage the hair cells in the cochlea. How much hearing you lose depends on the volume of the sound and how long you were around it. Ear infections . They can make fluid build up in the middle ear. Usually, the hearing loss from an ear infection is mild and goes away shortly. But if you don't treat the infections, they can lead to serious long-term problems. Perforated eardrum. An ear infection, loud sounds, trauma, or intense pressure in the ear from flying in an airplane or scuba diving can damage the eardrum, leaving a hole that may or may not heal. Depending on the size of the hole, there may be mild or moderate hearing loss. Cholesteatoma. This is a collection of skin that you can get in the middle ear when the eardrum collapses or when skin grows through a hole in the eardrum. Cholesteatomas grow over time and can lead to hearing loss by destroying the middle ear bones or, rarely, the inner ear. Illnesses or infections. Measles, mumps, syphilis, and meningitis are just a few of the conditions that can cause hearing loss. Meniere's disease. Symptoms of this inner ear disorder include: Dizziness Hearing loss that comes and goes Ringing in the ear Fullness in the ear Hearing loss in Meniere's disease usually gets worse but only involves one ear. Tumors. Cancer or benign tumors can cause severe hearing loss. This includes acoustic neuroma, paraganglioma, and meningioma. People who have one might also have numbness in their face or weakness and ringing in their ear. An object stuck in the ear. When something's in your ear that shouldn't be, it can block hearing. Earwax can sometimes build up and harden, which can make it hard to hear. Malformed ear. Some people are born with poorly formed ears. Trauma. Injuries like a skull fracture or a punctured eardrum can cause severe hearing loss. Medications. Some types of drugs -- including some antibiotics, large amounts of aspirin, chemotherapy drugs (carboplatin, cisplatin), and Vicodin (in large amounts) -- can cause hearing loss. Sometimes hearing will return once you stop taking the drug. In most cases, the hearing loss is permanent. Genes. Scientists have found genes that make people more prone to severe hearing loss, particularly as they age. Most of the time, newborn screening tests find genetic hearing loss, but it can show up later. Autoimmune disorders . Lupus and rheumatoid arthritis, for example, may affect hearing. It's one of the main features of several autoimmune disorders, including Cogan's syndrome, Wegener's granulomatosis, and Behcet's disease.