Hearing loss is a medical condition in which your auditory system does not function properly. With normal hearing, your outer ears pick up sound, which travels in your ear canal until it reaches the eardrum. Vibrations from your eardrum cause a chain of movement in your ear bones, which cause fluid in your inner ear to move. This movement is picked up by your inner ear hair cells, which transmit electrical signals to the brain, which are registered as sound.
Hearing loss occurs when one or more of these steps is hindered.