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.

Since the purpose of this article is to help you understand music better, let’s stick to sound waves for the rest of the article. Back in the 19th century, a guy named Heinrich Hertz did a lot of work measuring the different kind of waves. In his honor, the speed of waves was named after him. Hertz is the measurement of how many waves pass you in one second. Think about the ocean. If you take a couple of steps in and stand there with your feet in the water, if there is a lot of wind one ocean wave might past your feet every second. The ocean current would have a wavelength of 1 Hertz – one wave per second. Now think for a minute: how many Hertz (waves per second) do you think sound waves have? Actually, there’s a range – sound waves have a low end and a high end. So guess (no penalty if you’re off); what is the lowest wavelength for sound waves, and what is the highest?

The answer: the very longest (slowest) wavelength for sound is 20 Hertz. That means that 20 waves of sound pass you each second. The shortest (fastest) wavelength is 22 kiloHertz. If you remember the metric system, kilo means 1000, so for the shortest wavelength, 22,000 waves of sound pass you each second. The shorter and faster the wave, the higher the sound; the longer and slower the wave is, the lower the sound.

Let’s end the article by looking at the different categories of sound waves. The slowest sound wave is labeled “lower bass,” and it travels between 20 and 80 Hertz. Room resonance, very low thunder rumbling, and AC power hum are some of the sounds in this category. If you filter out this range, you lose a lot of richness and power.

“Upper bass” travels between 80 and 200 Hertz. Bass guitars and bass drums play in this range. A majority of the rhythm section’s energy is found in this wavelength.

“Lower midrange” is between 200 to 500 Hertz. Rhythm guitar, tom-toms, and lower piano play in this range. Leaving out this range would also sacrifice a lot of rhythm.

“Middle midrange” travels between 500 – 2500 Hertz. Violins, the upper range of electric guitars, upper piano, the snare drum, and most vocals fall within this range. Leaving out middle midrange would take most of the melody out of the music.

“Upper midrange” travels between 2,500 Hertz to 5 kilohertz. Harmonics and overtones fall within this range- not the melodies themselves, but the nuances of the sound that add to the “brightness” of a piece. Filtering out this part of the spectrum would leave a flatter, darker sound.

Two more to go. “Lower Treble” travels between 5 and 10 kilohertz. Upper overtones fall within this spectrum; however, the hiss sound of messy recording also falls within this range. Blocking it out would cause the loss of most of the musical brightness.

Finally, “Upper Treble” falls between 10 and 20 kHz. Up until the advent of the compact disk, few systems could accurately play this sound; as a result, many musicians blocked out all sounds above 10 kilohertz in order to decrease hiss. The difference between low and high-end stereo equipment has a lot to do with how they handle this region of sound; low-end systems can’t produce it accurately, but high-end systems are able to pristinely play this region of sound, resulting in an added richness and liveness.

All right, that was a lot of info in a short space. To sum it up: there are two kinds of waves – compressional and transverse. Radio and light waves are transverse; they can travel through a vacuum without any problem. Sound waves, on the other hand, are compressional – they need a medium, like air, to travel through in order to be heard. The speed of compressional waves as compared to transverse waves is about the difference between a snail and an airplane. The speed of sound is measured in Hertz, which tells us how many waves pass each second. Low sounds travel around 20 Hertz, while the very highest sounds travel at around 20,000. Finally, we looked at the different regions of sound and what instruments fell into each range. As a result of reading this article, I hope you have a greater appreciation for the skill that expert musicians demonstrate in blending the different frequencies to produce music.