The sounds we hear are the result of vibrations of air, fluid, and
solid materials in our environment. The vibrations produce sound waves, which
vibrate at a certain speed (frequency) and have a certain height (amplitude).
The vibration speed of a sound wave determines how high or low a sound is
(pitch). The height of the sound wave determines how loud the sound is
Hearing is the result of these sound waves traveling through the ear
and being converted into nerve impulses that are sent to the brain, which
Sound waves enter the
ear through the ear canal (external ear) and strike
the eardrum (tympanic membrane), which separates the ear canal and the middle
The eardrum vibrates, and the vibrations move to the bones of
the middle ear. In response, the bones of the middle ear vibrate, magnifying
the sound and sending it to the inner ear.
The fluid-filled, curved
space of the inner ear, sometimes called the labyrinth, contains the main
sensory organ of hearing, the cochlea. Sound vibrations cause the fluid in the
inner ear to move, which bends tiny hair cells (cilia) in the cochlea. The
movement of the hair cells creates nerve impulses, which travel along the
cochlear (auditory, or eighth cranial) nerve to the brain and are interpreted
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