Our ears have two functions, hearing and balance, but what do they hear and how? We can experience a whole world of sound due to the precise coordination of highly evolved anatomical, electro-chemical, and neurological processing systems. ‘Hearing sound’ describes the anatomy of the outer, middle, and inner ear along with the nerve signals sent to the brain. What happens in the brain’s hearing and language centres is not entirely clear, but the first stage in processing is to extract salient features from the stream of input data from the auditory nerve. Problems with hearing, including deafness and tinnitus, are explained along with how we make different sounds.