Grade of impairment	Audiometric ISO value	Performance	Recommendation	Comments added to the prior classification
0-None	≥25 dB	No or very slight hearing problem. Can hear whispers.	None	20 dB also recommended. People with 15–20 dB levels may have hearing problems. People with unilateral hearing loss may have problems even if the better ear is normal.
1-Slight	26–40 dB	Can hear and repeat words spoken in a normal voice at 1 m	Counseling. Hearing aids may be needed	Some difficulty in hearing but can usually hear normal level of conversation
2-Moderate	41–60 dB	Can hear and repeat words spoken in raised voice at 1 m	Hearing aids are usually recommended	None
3-Severe	61–80 dB	Can hear some words when shouted into better ear	Hearing aids needed. Otherwise lip-reading and signing should be taught	Discrepancies between pure-tone thresholds and speech discrimination score should be noted
4-Profound	≥81 dB	Unable to hear and understand even a shouted voice	Hearing aids may help understanding words. Additional rehabilitation needed. Lip-reading and sometimes signing are essential.	Speech is distorted, the degree depending on the age at which hearing was lost