Grades 3–5 · Organisms
How do tiny ear bones carry sound inward?
A sound reaches the eardrum as changing air pressure. This thin membrane moves back and forth. Three tiny middle-ear bones connect that moving membrane to the entrance of the inner ear.
In the diagramThree tiny bones link air motion to fluid motionEar canalMiddle earInner earEardrumMalleusIncusStapesFluidStapes footplate moves at the oval windowEnlarged links • no energy is created.
The malleus touches the eardrum. It moves the incus, which moves the stapes. The stapes has a small footplate at the oval window. Its movement pushes and pulls on the fluid behind that window.
The eardrum collects motion over a larger area than the stapes footplate. This area difference, together with the bones’ lever action, helps transfer sound energy from air into fluid. It raises pressure at the small output rather than creating extra energy.
Fluid motion then starts a traveling wave inside the cochlea, where sensory cells help turn movement into nerve messages. The drawing separates and enlarges the bones so their connections are easier to follow; their actual shapes and movements are much smaller.
About this explanation
Starting knowledge: Know that organs have parts that work together.
Sources
- NIH/NIDCD — How Do We Hear?
- NCBI Bookshelf · Neuroscience — The Middle Ear