As you know, there are a lot of vibrations in the world, a lot of waves. Music itself is a series of wave vibrations. We will hone in on music a little later, but first: how many kinds of wave vibrations can you name? Think about it for a minute. For instance, an X-Ray is a wave vibration. Can you name three others? Four? There are 9 forms all together, listed in the next paragraph.

The nine forms of waves are as follows: sound waves, radio waves, microwaves, infared waves, visible light, ultraviolet light, x-rays, gamma rays, and cosmic waves. How did you do? I could only name about three of them before I started research for this article, so don’t feel to bad if you could only name one or two. And if you named all nine – congratulations! You should have written this instead of me!

Okay, next question. There are two different classes of waves – compressional and transverse. Do you have any idea what the difference is? Here’s a hint – it has to do with how the waves travel. Think about it for a second – the answer is in the next paragraph.

Compressional waves require a medium to travel through, while transverse waves do not. Sound complicated? Not really. Sound waves are compressional – they have to travel through a medium, and can’t travel through a vacuum. You know that old saying, “In outer space, no one can hear you scream”? It’s true – sound waves have to travel through something, and there is nothing for sound to travel through in outer space. Sound waves can travel through the mediums of air, water, and even solids. (Have you ever seen one of those old cowboy movies where the Indians put their ear to the ground to hear how far away the bad guys were? The sound waves were traveling through a solid, the ground.) Of the 9 kinds of waves listed above, only sound waves are compressional – only sound waves require a medium to travel through. The rest are transverse, which means that they can travel anywhere, even through outer space, without any problem. They don’t need something to travel through.

The purpose of this article is to help you understand the sound waves that comprise music a little better, but before we get there, I have one more thought experiment for you. How fast do the different kinds of waves travel?

The answer is: the speed of light for transverse waves and “a lot slower” for compressional waves. Have you ever been at a baseball game and seen the batter swing, waited a few seconds, and then heard the crack of the bat? That is because the sound wave, a compressional wave, was traveling through air, at a fairly slow speed. The image of the batter was traveling much faster, at the speed of light, so it reached your eyes several seconds before the sound wave reached your ears. Sound travels around 775 miles per hour; transverse waves travel at around 670,000,000 miles per hour. So light travels about 865,000 times faster than sound. That’s about the difference in speed between a snail and an airplane, to put it in terms that are easier to visualize. Imagine a slug racing a Boeing 747 and you can visualize the difference in speed between sound and light.

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