What is Sound?

As we have already learned, the ear does not hear. What the ear does do is translate sound waves into electrical signals. But that just begs a question, what is a sound wave and what is an electrical signal? Or, put otherwise, what is it that the ear is translating from and what is it translating to?

For now, we'll just deal with the question of sound waves and leave the issue of electrical signals for another time. So, the question is – what is a sound wave?

The short answer to that question is that sound is a wave (a sound wave, to be exact). But again, that just leads to yet another question. What is a wave? The technical answer is that a wave is a disturbance in a particular medium. The less technical answer is that a wave is a disturbance in a particular medium.

Okay, I admit it, I don't have a less technical answer. I do, though, have a less technical example.

Imagine of a bunch of guys waiting in line. The last guy in line gets a bit impatient and pushes the guy in front of him. This forces the guy in front of him to lunge forward and push the guy in front of him, which in turn forces that guy to push the guy in front of him. This process continues until the force of the original push dies down. Thus a strong push will lead to more people getting pushed, a weak push to less people getting pushed.

What's important to note is that it is the push that is getting transferred. And that push is simply the energy that the first guy transferred into the guy in front of him. So what we have here is a transfer of energy in a group of guys. The transfer of energy is what we call a disturbance (as the other guys in the line will attest to). And the group of guys is the medium through which this disturbance traveled.

So it is with sound waves. Instead of a group of guys, we have a group of air molecules. That is the medium. And instead of a push, we have some means of setting those air molecules into motion (such as clapping our hands, plucking a string, singing a song, etc.). And finally, we have a repeating, back-and-forth push, rather than a one time shove.

Now all of this reveals a rather interesting point. At the end of the day, sound is simply a form of travelling energy. As such, it's worth wondering, what exactly is energy. What is it that is being transferred from one place to another?

Energy, it seems, doesn't have any 'physical' properties. It has no mass, length, height, color, etc. It is an immaterial entity. although one that can be converted into mass. That's what Einstein's famous equation E=MC2 means. Energy can be converted into matter and matter can be converted into energy. They are equivalent, but they are not the same thing. Matter has mass, length, height, etc. and energy does not. Matter is material, energy is not.

So sound waves are an immaterial entity travelling through a material medium. The matter, though, is merely the stage on which the immaterial runs the show. Energy is what hits the ear and energy is what the ear sends to the brain. It is simply the form of energy that changes, but at the heart of the whole process is energy — an immaterial entity.

And that is worth thinking about.

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