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Deafness is impaired hearing, and it is a great social and educational handicap. The plight of a blind person or a lame man can easily be visualized by everyone, and they evoke sympathy, but no one sympathizes with a deaf person, as his handicap is not noticeable. To understand how hearing becomes impaired, it becomes necessary to understand the nature of sound.

Types of Deafness
Deafness Conductive Sensory–neural
Site of lesion External ear and middle ear. Inner ear, eight erve and central connection.
Rinse test Bone conduction better then air conduction. Air conduction better ear.
Weber test Liberalized to the worse ear. Liberalized to the better ear.
Pure tone Audiometry Bone conduction threshold normal. Air conduction threshold increased. Both air and bone conduction thresholds are increased.
Hearing loss Not more then 60 dB. May be more than 60 dB.
Speech Speaks in a low voice. Speaks loudly.
Speech discrimination Good. Poor.
Recruitment Absent. Present in cochlear deafness.