The Science of Music

What is music?

Music is organized sound. More specifically, music is any arrangement of sounds with artistic intent. But in order to understand how music works, we first need to understand how sound works.

How does a speaker work?

What do you think? When you hear music coming out of a speaker, what is actually happening?

Watch the video to find out. Try to answer these questions while watching:

  • What is oscillation?
  • Does air travel across the room when a sound is made?
  • What is a medium?
  • What other mediums can sound travel through?

Production of sound _ Mechanical waves and sound _ Physics _ Khan Academy.mp4

When a speaker makes sound, it oscillates at a specific frequency. As the membrane of a speaker vibrates, it also vibrates the air surrounding it, which creates a wave of air that travels across the room. When that wave reaches your ear, your brain perceives it as sound, and you "hear" it.

Have you ever tried talking or clapping under water before? Why does it sound different when you're under water?

What would happen if you clapped in outer space?

Sounds are vibrations that are perceived by a human or animal's ears.

It's an old riddle, and you've probably heard it before:

"if a tree falls in a forest, and no one is around to hear it, does it make a sound?"

What do you think the answer is?

Why is there a delay?

The further you are from the source of a sound, the longer it takes for it to get to you. When there's thunder and lightning, we always see the flash before we hear the thunder. This is because the sound vibrations are traveling through the air in a wave, at a speed of 767 miles per hour.

Sometimes, this wave can be visible. When an explosion goes off, a tremendous amount of energy is released. The vibrations traveling through the air are so strong that they refract light and create a slight shadow. Take a look at this video and look for the shadow effect of the shock wave. As soon as the shadow reaches the camera, we hear the deafening sound of the explosion.

You can actually see the sound traveling!

Huge Explosion and Shockwave.mp4

Sound waves

Sound travels in pressure waves. When drawing a wave on paper, we give it a curvy wave shape, but if we could really see it, it would look like the top of this picture.

Changing the wave in two directions has different effects. If we "smooshed" the wave together, the pitch would be raised. If we stretched the wave out, it the pitch would lower.

If we made the wave higher and lower, the wave would be louder. And if we made the wave more "leveled", it would be quieter.

Click this button to go to a website that lets you see the sound waves when you press the notes on a keyboard. See how the waves are further apart when you play low notes, and closer together when you play high notes.

Doppler Effect (car horn) VERY Noticeable.mp4

The Doppler Effect

Have you ever noticed that when a police car drives by, the pitch of the siren changes as is passes you? It sounds higher when it approaches, and gets lower as it's going away. This is called the doppler effect. The doppler effect happens because the waves are being "smooshed" as the car is driving fast and approaching you, and the waves are being "stretched" as the car drives away. The speed of the car makes the sound wave's frequency higher as it's getting closer to you. Watch this video to see the doppler effect in action.

Pitch & Wave Length

The longer a wave is, the lower the pitch. The shorter a wave is, the higher the pitch gets. Click on the waves to the right. What do you notice about the pitches as the wave length gets smaller and smaller?

Guitar Strings

When a string instrument makes a sound, the strings vibrate at a certain frequency. You can see the characteristics of the sound wave if you take a video from inside a guitar. Watch the video and see how the frequency of the lower sounds is larger, and the frequency of the higher notes is shorter.

The reason you can see the waves in this video is because the rate of the shutter speed of the camera is close to the frequency of the wave. Your eye wouldn't be able to see this by itself.

Click the link to see how a wave's frequency is related to its pitch.

Practice creating a song:

Click on the button to the right. Using the website, make a short looping song by placing notes vertically and horizontally on the grid. Add percussion on the bottom.

Today's assignment:

Click on the Microsoft Form link and answer the questions about this lesson. Before you submit, make sure to save your song and copy and paste the link in the form.