deafness

Deafness is the partial or total inability to hear. In clinical terms, hearing loss is measured in decibels hearing level (dB HL). Normal hearing generally falls within 0 to 25 dB HL; higher thresholds indicate varying degrees of loss, from mild to profound. The word deafness is sometimes used to describe severe or profound loss that significantly affects daily communication, and in many communities it is associated with the use of sign languages and Deaf culture.

Hearing loss can be classified by its origin as conductive, sensorineural, or mixed. Conductive loss involves problems in the outer or middle ear that block sound transmission. Sensorineural loss stems from damage to the inner ear or auditory nerve. Mixed loss includes both conductive and sensorineural components. Severity ranges from mild to profound and may be present at birth (congenital) or develop later (acquired).

Common causes include genetic conditions, prenatal infections, or complications at birth; infections such as meningitis or otitis media; prolonged exposure to loud noise; age-related degeneration (presbycusis); ototoxic medications; head trauma; and tumors affecting the auditory system.

Diagnosis relies on audiological testing such as pure-tone audiometry, tympanometry, otoacoustic emissions, and, when needed, auditory brainstem response. Management depends on the type and severity and may involve hearing aids, cochlear implants for severe cases, bone-anchored or other assistive devices, and communication approaches such as sign language, lip reading, and captioning. Prevention focuses on protecting against loud noise, treating ear infections, and preventing infections that can damage the auditory system.

Global prevalence is substantial, with hundreds of millions experiencing some degree of hearing loss; access to diagnosis and support varies by region and affects education, communication, and quality of life.