I am sitting at the piano on a rainy day. I close my eyes and push down on one of the keys. Ahh! A nice, clear middle C rings through the house. I move my finger to the left and strike one of the black keys… B flat…I think. I am not much of a piano player, but I hear the difference between those two notes. The question is HOW can I tell the difference? My eyes are closed, so I can’t see the keys. Do my ears tell me so? Let’s explore this.
The sound waves from the piano travel through air and are collected by the outer ear and sent down the ear canal to the ear drum. Here is where the engineering begins. A sound wave is the compression and expansion of air molecules: acoustic energy. As the waves hit the ear drum, they force the drum, and the three tiny ear bones attached to it, to vibrate. The vibration of these parts: mechanical energy.
At the ear drum, the sound waves change to physical movement. Engineers call this change: transduction. The ear drum is not only a part of our anatomy. It is a transducer.
The sound waves from the piano keys have moved the structures in the middle ear. As this movement travels inward, it causes activity in the inner ear. The Cochlea is the fluid filled organ of hearing in the inner ear. The structures within it “sort out” the fluid waves traveling though it and send signals toward the brain.The engineering continues.
The Cochlea has been stimulated by the mechanical energy of the middle ear. This causes waves of fluid to travel through the Cochlea. Movement within this fluid environment is hydraulic energy and the point where the middle ear and inner ear connect is another transducer.
Let’s take a look at the path of my middle C and B flat, so far. I strike the keys and create sound: acoustic energy. The outer ear collects the sound and guides it to the ear drum where it vibrates the eardrum and the middle ear: mechanical energy. Hydraulic energy is created within the Cochlea as fluid waves are sent through it.
One more piece of engineering: as the fluid waves travel within the Cochlea, they push on thousands of tiny nerve fibers called hair cells. The “roots” of these hair cells are stimulated, converting the hydraulic energy to the “language” of the brain and the nervous system: electro-chemical energy.
This is a long explanation for something that happens in “split seconds”… and… after all of this engineering and activity, I still have not heard my middle C and my B flat (let alone the difference between them). WHY NOT?
The answer…Next Time!
