In the ear, vibrations in the air (sound) are converted into biochemical signals to the brain. This is quite complex, but the last stage happens when tiny hairs in the inner ear are “tickled” by the sound waves, and those tickles are sensed by the brain as sound!
I’m not an expert, but I think different things can cause deafness – sometimes it’s problems with the eardrum or middle ear, sometimes it’s the nerves in inner ear. Some of these can be treated but others cannot. Does anyone else have a better answer? 🙂
I’m assuming you mean deaf?? As Martain mentioned there are a number of different causes. Damage to your middle and inner ear is the most common. In the inner ear are a series of tiny bones that transfer the vibrations of the air to a shell like structure called the cochlea. The cochlea contains many tiny hairs that send signals to the brain in response to these vibrations. Loss of hearing can occur if the bones of the middle ear become damaged, so they can no longer transfer the vibrations, or if the Cochlea is broken, you now cannot sense the vibrations. It’s possible to lose the ability to sense specific frequencies of sound by damage to individual hairs within the Choclea.
Lots of stuff can cause deafness. Some people are born deaf but others become deaf later in life. This can happen due to accidents or damage from things like loud noises, or from diseases like measles.