The inner ear consists of two main parts; the snail-shell-shaped cochlea (the hearing organ) and the vestibular system (the balance organ). For the purpose of this description of hearing, we will refer only to the cochlea. Vibrations from the middle ear bones are conducted to the fluid-filled cochlea through a small opening, called the oval window. These vibrations travel through the cochlea from the base to the tip along a series of membranes which house the cells, called “hair cells”, that detect the vibrations. There are many thousands of these specialised cells in each ear, each is tuned to detect a specific frequency of vibration, or “pitch”. Cells near the base of the cochlea are responsible for detecting the higher pitches, cells near the tip of the cochlea are responsible for detecting deeper pitches.
Once a vibration/sound has been detected by the hair cells, they transmit tiny electrical signals from the inner ear, via the hearing nerve (the vestibulocochlear nerve) to the brain-stem and brain where the signals are decoded and the sound is “heard”.