Question: What is the reason behind deafness ?

Nancy Carlisle answered on 24 Jun 2014:

Just like blindness, deafness can be caused either by problems with the receptors that pick up the signals or damage to the brain areas that process the signals. So, an injury to the ear that reduces the signals going through (like rupturing your eardrum) can cause deafness, and so could a lesion in auditory cortex (the part of the brain that processes auditory signals). Long exposure to loud noises can also cause deafness, so be sure you don’t listen to you headphones set too loud!