To standardize the way in which severity of hearing loss is reported, WHO has
adopted a grading system based on audiometric measurements. This system is
a revision of an earlier approach adopted by WHO, and differs from the earlier
system in that measurement of onset of mild hearing loss is lowered from 26 dB
to 20 dB; hearing loss is categorized as mild, moderate, moderately-severe, severe,
profound or complete; and unilateral hearing loss has been added. In addition
to the classifications, the revised system provides a description of the functional
8 Audiograms show the minimum intensity, in decibels, a person can hear at different frequencies of sound. This is typically depicted
in graph form following a hearing test, as measured by an audiometer.
consequences for communication that are likely to accompany each level of severity (148).
This revised grading system is presented in Table 1.3 below.

Table 1.3 Grades of hearing loss and related hearing experience* Grade Hearing threshold‡ in better hearing ear in decibels (dB) Hearing experience in a quiet environment for most adults Hearing experience in a noisy environment for most adults Normal hearing Less than 20 dB No problem hearing sounds No or minimal problem hearing sounds Mild hearing loss 20 to < 35 dB Does not have problems hearing conversational speech May have difficulty hearing conversational speech Moderate hearing loss 35 to < 50 dB May have difficulty hearing conversational speech Difficulty hearing and taking part in conversation Moderately severe hearing loss 50 to < 65 dB Difficulty hearing conversational speech; can hear raised voices without difficulty Difficulty hearing most speech and taking part in conversation Severe hearing loss 65 to < 80 dB Does not hear most conversational speech; may have difficulty hearing and understanding raised voices Extreme difficulty hearing speech and taking part in conversation Profound hearing loss 80 to < 95 dB Extreme difficulty hearing raised voices Conversational speech cannot be heard Complete or total hearing loss/deafness 95 dB or greater Cannot hear speech and most environmental sounds Cannot hear speech and most environmental sounds Unilateral < 20 dB in the better ear, 35 dB or greater in the worse ear May not have problem unless sound is near the poorer hearing ear. May have difficulty in locating sounds May have difficulty hearing speech and taking part in conversation, and in locating sounds * The classification and grades are for epidemiological use and applicable to adults. The following points must be kept in mind while applying this classification: • While audiometric descriptors (e.g. category, pure-tone average) provide a useful summary of an individual’s hearing thresholds, they should not be used as the sole determinant in the assessment of disability or the provision of intervention(s) including hearing aids or cochlear implants. • The ability to detect pure tones using earphones in a quiet environment is not, in itself, a reliable indicator of hearing disability. Audiometric descriptors alone should not be used as the measure of difficulty experienced with communication in background noise, the primary complaint of individuals with hearing loss. Unilateral hearing loss can pose a significant challenge for an individual at any level of asymmetry. It therefore requires suitable attention and intervention based on the difficulty experienced by the person. ‡ “Hearing threshold” refers to the minimum sound intensity that an ear can detect as an average of values at 500, 1000, 2000, 4000 Hz in the better ear (148, 156, 157).

The classifications used in Table 1.3 follow the recommendations of the International
Classification of Functioning, Disability and Health (ICF) proposed by WHO in 2001.
As stated in the ICF, a person with the slightest reduction in hearing sensitivity has
a potentially “disabling” condition. The ICF defines a person’s state of health along
three dimensions which are outlined in Box 1.1 (158). According to the ICF, the
disability experienced is determined not only by the individual’s hearing loss but also
by the physical, social and attitudinal environment in which the person lives, and
the possibility of accessing quality EHC services. Therefore, a person with hearing
loss who does not have access to hearing care, is likely to experience far greater
limitations in day-to-day functioning and thus higher degrees of disability.