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Hearing depends on a rapid series of energy changes. A vibrating source, such as the vocal cords, creates sound waves -- acoustic pressure waves moving through the air.
When those waves reach the eardrum, the ear converts the acoustic energy (sound) into mechanical energy (physical movement) through the three small bones of the middle ear. That mechanical motion then pushes on the fluid-filled cochlea, changing the energy into hydraulic pressure waves. As these waves travel through the cochlea, they stimulate thousands of tiny hair cells, which convert the motion into electrochemical nerve signals that the brain recognizes as sound.
Lumenhearing.com explains it this way: "The pressure waves strike the tympanum, causing it to vibrate. The mechanical energy from the moving tympanum transmits the vibrations to the three bones of the middle ear. The stapes transmits the vibrations to a thin diaphragm called the oval window, which is the outermost structure of the inner ear. The structures of the inner ear are found in the labyrinth, a bony, hollow structure that is the most interior portion of the ear. Here, the energy from the sound wave is transferred from the stapes through the flexible oval window and to the fluid of the cochlea. The vibrations of the oval window create pressure waves in the fluid (perilymph) inside the cochlea. The cochlea is a whorled structure, like the shell of a snail and it contains receptors for transduction of the mechanical wave into an electrical signal. Inside the cochlea, the basilar membrane is a mechanical analyzer that runs the length of the cochlea, curling toward the cochlea's center."
Transduction is the process of changing a signal or form of energy into another form.
According to the Merriam-Webster definition, it means carrying over or changing a message from one system to another, though the exact meaning varies by scientific field.
Human history is filled with examples of harnessing and transforming energy: wind moving sails, water turning a mill wheel to grind grain and the force of the Niagara River driving turbines that generate electricity for much of the eastern United States.
Examples of transduction are everywhere -- from massive power projects to tiny insects. Fireflies, for instance, produce light through a chemical reaction in specialized abdominal organs, a process called bioluminescence.
We live in a highly organized, highly energized world, and our bodies are constantly changing, modulating and transducing energy.
The next time you hear birds singing in your yard, you can simply enjoy the sound without thinking about acoustic energy becoming mechanical energy, then hydraulic energy and finally electrochemical signals that you instantly recognize as robins, cardinals or wrens.
The miracle of hearing happens within us instantly through this remarkable transduction of energy. Is it not true that we are fearfully and wonderfully made?
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Jeff Bayliff is owner of Hear the Birds Hearing Aid Center in Lock Haven, Pa.