Hearing impairment is a symptom of many injuries and diseases. Therefore it may be expressed at any age and classified in many ways, such as prelingual vs. postlingual, conductive vs. sensorineural, syndromal vs. nonspecific, and genetic vs. acquired. Hearing is significantly impaired when loss exceeds 25 decibels (dB). Individuals with at least an 80 dB loss in both ears are profoundly deaf unless ameliorated by a hearing aid or surgery, this loss is so severe as to preclude successful processing of auditory information. Untreated prelingual deafness interferes with speech as well as hearing, leading in its extreme form to the condition formerly known as deaf mutism.