There are many causes and kinds of hearing loss.
There are two large classes of hearing loss. First is a conductive hearing loss. This means that the sound conduction pathways from the air to the inner ear are in some way blocked or impaired. This type of hearing loss causes sounds to be softer and more distant than normal. In general, conductive hearing loss is usually more correctable. Causes of conductive hearing loss includes ear wax, middle ear fluids, eardrum perforations, middle ear tumors, such as cholesteatomas, and finally bony misconnections such as incus erosion, dislocation, or fixation of the last hearing bone called the stapes. An examination by a physician and/or a hearing test will clarify the cause of this type of hearing loss. See image below.
A second class of hearing loss is called a sensory neural hearing loss. Sensory neural hearing loss is caused by a disorder in the inner ear or the nerve from the inner ear to the brain. Rarely, brain injuries themselves can also cause this type of hearing loss. The most frequent causes of sensory neural hearing loss include the aging process and the exposure to loud sounds. Aging causes roughly 1 dB hearing loss for every year that we live. At age 100 it is likely to have a severe sensorineural hearing loss in the high frequency hearing range. Similarly, if we are exposed to loud sounds everyday, we will lose our hearing. Sounds which are louder than 85 dB will ultimately cause hearing loss. This type of loud sound exposure adds up over a lifetime. Other diseases that cause sensorineural hearing loss includes reversible infections like Lyme's disease, thyroid disorders, diabetes, and Meniere's disease. Only a doctor can help to determine the cause of a sensorineural hearing loss.
The most dangerous types of hearing loss involve hearing loss in one ear. This can be a warning sign of more serious problems. Cancer of the throat can first appear as a hearing loss on one side. Similarly, brain tumors (usually benign) can also appear first with a unilateral (one sided) hearing problem. Not all unilateral hearing loss is deadly. Many marksmen have a unilateral loss from the use of their weapons. Almost all veterans will experience some hearing loss from their training and use of guns. Only by testing your hearing will you be able to determine the severity and type of hearing loss.
You might find these resources helpful:
- Medlineplus.gov - hearing disorders and deafness page
- National Institute on Deafness and Other Communication Disorders