Defects of the Human ear
Several defects of the ear lead to hearing loss or even deafness. Hearing loss, or hearing impairment, happens when there is a problem with one or more parts of the ear or ears.
The hearing loss may be congenital or due to middle ear fluid, serious infections, such as meningitis, head injury, listening to very loud music, especially through headphones, repeated exposure to loud sounds, such as machinery.
One of the common causes of conductive hearing loss is blockade of the external auditory meatus with wax secreted from ceruminous glands in the skin lining the meatus. In some people wax accumulates in the meatus and hardens, sometimes pressing against the eardrum. Normal hearing is usually restored after the hardened wax is removed with a special syringe.
Another cause of conductive hearing loss, is a perforated eardrum. Perforation can be caused by infection in the middle ear or by mechanical injury resulting from a nearby explosion or a sudden blow to the head. Injury to the head can also cause the ossicles of the middle ear to become disconnected from one another, thus breaking the conductive path to the cochlea.
Malfunction of the cochlea and acoustic nerve can be the cause of hearing loss, even though vibrations are conducted perfectly into the inner ear. Such hearing loss is called sensorineural (perceptive) hearing loss. Acquired forms of this condition can result from infection, head injury, blast from explosions or exposure to excessive noise.