<P> The severity of a hearing loss is ranked according to ranges of nominal thresholds in which a sound must be so it can be detected by an individual . It is measured in decibels of hearing loss, or dB HL . The measurement of hearing loss in an individual is conducted over several frequencies, mostly 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz . The hearing loss of the individual is the average of the hearing loss values over the different frequencies . Hearing loss can be ranked differently according to different organisations; and so, in different countries are different systems in use . </P> <P> Hearing loss may be ranked as slight, mild, moderate, moderately severe, severe or profound as defined below: </P> <Ul> <Li> Slight: between 16 and 25 dB HL </Li> <Li> Mild: <Ul> <Li> for adults: between 26 and 40 dB HL </Li> <Li> for children: between 20 and 40 dB HL </Li> </Ul> </Li> <Li> Moderate: between 41 and 54 dB HL </Li> <Li> Moderately severe: between 55 and 70 dB HL </Li> <Li> Severe: between 71 and 90 dB HL </Li> <Li> Profound: 91 dB HL or greater </Li> <Li> Totally deaf: Have no hearing at all . This is called anacusis . </Li> </Ul> <Li> Slight: between 16 and 25 dB HL </Li>

National programme for prevention and control of deafness-wikipedia