A degree of hearing loss, temporary or permanent due to many causes. Hearing loss can be caused by illness, disease, or by exposure to excessively high noise levels. Affects 25-50 million people in USA of all ages. Hearing impairment as generally used means a hearing loss of a mild, moderate, or severe degree as apposed to ?Deafness? which is generally described as little or no residual hearing with or without the aid of an assistive listening device. Hearing Impaired persons are particularly victimized by long reverberation times.