You will now create an outline for your final assignment.
In this lesson you learned about sound waves; how they move energy, how they are measured, and how they make loud, quiet, high and low sounds. You took notes on almost every page of the lesson, and it's time to use them, as well as other information presented, to compose your own multimedia project, or write a final essay, in which you describe and summarize all that sound-wave knowledge you've collected.
As you compose your project, try to think of ways to connect, either graphically or in writing, the ways in which the properties of sound waves relate to different types of sound. One idea is to create drawings of loud, quiet, high and low sound waves,and the ways in which these properties are measured.
If you create a multimedia project that requires a social-media, video or audio platform that is not directly offered by this lesson, you will need to post it to a file-sharing site (Dropbox, Google Drive and Microsoft Teams are examples) and then upload the link to the Write It plug-in. Here are some ideas for what you might want to do:
Use Organize It to outline your ideas. You can review your notes in “My Work” as well as any of the following videos and glossary terms.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
All waves transfer energy, but the way they do it varies. A longitudinal wave can carry energy through air, water and solids, and it does it by compression and expanding the medium in the same direction it transfers the energy.
This compression and expansion can be measured in different ways:
1) Compression and Rarefaction: A compression is a point where the medium is at its most squished--or maximum density. A rarefaction is a point where the medium is most spread out--or least dense.
2) Amplification: Amplification is the measurement of how far the particles are pushed from their resting state (equilibrium).
3) Wavelength: The wavelength is the length of one wave cycle (compression to compression, or rarefaction to rarefaction.
Longitudinal waves need particles to push the energy. That means they can travel through gas, liquids and solids, but not through a vacuum. Sound is a longitudinal wave, for instance, and there is no sound in space.
Feel that beat? That's the longitudinal wave.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
Do you hear that? That is energy being transferred through a medium, in a wave pattern, to your ear. That is sound.
Sound is energy that vibrates a medium, and those vibrations travel in waves. The way those waves interact with the medium determines the way the sound, well, sounds, One of the most obvious sound qualities is volume. And that volume--the "loudness" of a sound--depends on energy.
If the energy being transferred is low, the particles get pushed a small distance, and the sound is quiet. If the energy being is high, the particles are pushed a farther distance, and the sound is loud.
And we can measure this by measuring the sound wave's amplitude--the distance each particle is pushed from its resting place.
Take a drum and hit it. The energy from your hand transfers to the drum, which vibrates the air around it, making a sound. Now increase that energy--hit the drum hard, and the drum pushed the air even farther. Same sound, but the higher amplitude means it's louder and can travel farther.
So, hit the dance floor and pump up the amplitude.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
A sound like this (high pitch) and a sound like this (low pitch) are different. But how? Both waves have the same amount of energy--each particle is getting pushed the same distance, therefore they are the same volume--but the rate at which they vibrate is different.
The rate of vibrations per second is called frequency. If the vibrations are more frequent, the higher the pitch. If the vibrations are less frequent, the lower the pitch.
To change the pitch of a sound, you have to change how many times the medium vibrates per second. Take a guitar string, for instance. As you tighten the string, the number of vibrations the string produces per second (frequency) increases and so does the pitch. Lower that string tension, and the vibrations per second (frequency) decrease and so does the pitch.
So hit that dance floor again, and this time, feel the vibrations--per second.