Background Speech frequency 500-3000Hz Normal hearing Sound conduction Sound perception( cochlea) Sound analysis(retro-cochlea) Deafmutism Profound hearing loss No language speech perception Language development quit(6M-6Y) Postlingual deafness deafness present following language developedBackground ◼ Speech frequency 500-3000Hz ◼ Normal hearing ◼ Sound conduction ◼ Sound perception (cochlea) ◼ Sound analysis (retro-cochlea) ◼ Deafmutism: ◼ Profound hearing loss. ◼ No language speech perception ◼ Language development quit (6M-6Y) ◼ Postlingual deafness ◼ deafness present following language developed