A hearing impairment signifies a full or partial loss of the ability to detect or discriminate sounds due to an abnormality associated with the physiology, anatomy or function of the ear. A hearing impairment can be described in terms of the:
A student with hearing impairment may use speech and/or sign to communicate. Some students who use sign prefer to be referred to as Deaf as they identify with the unique culture of the Deaf Community and perceive their deafness as a difference, not a disability.
(Reference: http://education.qld.gov.au/studentservices/learning/disability/generalinfo/hearing/what-is-hi.html )