• Entry
  • Reader's guide
  • Entries A-Z
  • Subject index

The World Health Organisation (WHO), in its factsheet on deafness and hearing impairment, refers to hearing impairment as “the complete or partial loss of the ability to hear from one or both ears. The level of impairment can be mild, moderate, severe or profound.”

The classifications are based on hearing thresholds (see Table 1, next page), most commonly measured using a standard procedure known as pure tone audiometry. In this approach, a measure of the quietest sound an individual can perceive is recorded at a number of different frequencies of sound. Plotting these values creates the audiogram.

WHO estimates from 2001 suggest that if an audiogram were to be recorded for every individual on the planet, approximately 600 million people worldwide would have a hearing loss affecting ...

    • Loading...
    locked icon

    Sign in to access this content

    Get a 30 day FREE TRIAL

    • Watch videos from a variety of sources bringing classroom topics to life
    • Read modern, diverse business cases
    • Explore hundreds of books and reference titles