When someone speaks or bangs a drum or makes any kind of movement, the air around them is disturbed, creating a sound wave of alternating high and low frequency. These waves are detected by the ear and then interpreted by the brain as words, tunes or sounds.
Consisting of air-filled cavities, labyrinthine fluid-filled channels and highly sensitive cells, the ear has external, middle and internal parts. The outer ear consists of a skin-covered flexible cartilage flap called the ‘auricle’, or ‘pinna’. This feature is shaped to gather sound waves and amplify them before they enter the ear for processing and transmission to the brain. The first thing a sound wave entering the ear encounters is the sheet of tightly pulled tissue separating the outer and middle ear. This tissue is the eardrum, ortympanic membrane, and it vibrates as sound waves hit it.
Beyond the eardrum, in the air-filled cavity of the middle ear, are three tiny bones called the ‘ossicles’. These are the smallest bones in your entire body. Sound vibrations hitting the eardrum pass to the first ossicle, the malleus (hammer). Next the waves proceed along the incus (anvil) and then on to the (stapes) stirrup. The stirrup presses against a thin layer of tissue called the ‘oval window’, and this membrane enables sound waves to enter the fluid-filled inner ear.
The inner ear is home to the cochlea, which consists of watery ducts that channel the vibrations, as ripples, along the cochlea’s spiralling tubes. Running through the middle of the cochlea is the organ of Corti, which is lined with minute sensory hair cells that pick up on the vibrations and generate nerve impulses that are sent to the brain as electrical signals. The brain can interpret these signals as sounds.
What is vestibular system?
Inside the inner ear are the vestibule and semicircular canals, which feature sensory cells. From the semicircular canals and maculae, information about which way the head is moving is passed to receptors, which send electrical signals to the brain as nerve impulses.