WHOの最近の分類 Grade of impairment Corresponding audiometric ISO value 0 - No impairment 25 dB or better (better ear) No or very slight hearing problems. Able to hear whispers. 1 - Slight impairment 26-40 dB (better ear) Able to hear and repeat words spoken in normal voice at 1 metre. 2 - Moderate impairment 41-60 dB (better ear) Able to hear and repeat words spoken in raised voice at 1 metre. Hearing aids usually recommended. 3 - Severe impairment 61-80 dB (better ear) Able to hear some words when shouted into better ear. 4 - Profound impairment including deafness 81 dB or greater (better ear) Unable to hear and understand even a shouted voice. The audiometric ISO values are averages of values at 500, 1000, 2000, 4000 Hz. http://www.who.int/pbd/deafness/hearing_impairment_grades/en/index.html など。