Sound intensity is measured in a unit called decibels. Hearing loss is denoted by the decibel level at which point sounds are audible (but perhaps not intelligible) at various frequencies across the speech spectrum. The larger the decibel number, the greater the hearing loss. Labels are often associated with various ranges of decibel hearing loss. For example, the following ranges are often used to describe hearing loss for infants and young children:
Audiograms are used to chart a person's hearing loss.
Individuals with Disability Educational Act defines "hearing impairment" as "an impairment in hearing, whether permanent or fluctuating, that adversely affects a child's educational performance but that is not included in the IDEA definition of deafness. Deafness is defined by IDEA as "a hearing impairment that is so severe that the child is impaired in processing linguistic information through hearing with or without amplification, that adversely affects a child's educational performance.
One sometimes hears the term "percentage hearing loss" - such as, "That person has an 80% hearing loss". This is meaningless, as hearing loss is not measured in percentages.
"Acoustics, Audition, and Speech Reception" (videotape) by Daniel Ling. (available from Auditory-Verbal International at 703-739--1049).
"Facilitating Hearing and Listening in Young Children: Early Childhood Intervention Series, 2nd edition", by Carol Flexor (available from A.G. Bell Assoc.202-337-8767).
"Audiology, 6th ed.", by Hayes Newby and Gerald Popelkla, Prentice-Hall, c. 1992.