1. Unit 13 – Section 1 “What is Sound?”

2. I. Vibrations and Sound Sound is created by vibrations.
A vibration is the complete back-and-forth motion of molecules (particles).
Sound waves are longitudinal (compressional) waves because of how they travel.
1. In a longitudinal wave, the molecules of a media vibrate back and forth (move parallel) along the path that the sound wave travels.
Sound is transmitted through the vibrations and collisions of the molecules(particles).

3. One way sound is made

4. Remember that sound waves are longitudinal waves
Remember that sound waves are longitudinal waves. They carry sound - NOT AIR. Air is only the medium through which sound waves travel.

5. II. Waves Waves ONLY transfer energy.
If anything else besides energy was transferred, such as air, wind gusts from music speakers would blow you over!

6. III. Transmission of Sound
All sound waves require a medium which makes them a mechanical wave.
Most of the sounds we hear have traveled through the air.
Sound waves can also travel through other media like liquids or solids. For example sound waves can also be transmitted through:
i. water
ii. glass
iii. solids

7. Water

8. Air

9. Solid

10. IV. Is there sound in space?
Sound does NOT exist in space.
Sound waves occur when molecules in a medium vibrate. Space is a vacuum and doesn’t have any media so there aren’t any molecules to vibrate.
No vibrations = no sound
No, because there are no particles to vibrate. Sound can not travel. Sound must travel through air or some other medium to reach your ears and be detected.

11. V. Hearing Loss and Deafness
Many parts of the ear must work together for you to hear sound.
If any part of the ear is damaged, hearing loss or deafness may result.
Short exposures to loud sounds can be painful and cause hearing damage or
permanent deafness.

12. In your notes… Click here to learn how you hear sound.
Click here to watch a few third graders describing how we hear sound waves

13. Quickie Quiz Sound travels as a. transverse waves.
b. longitudinal waves.
c. shock waves.
d. airwaves. b

14. In your notes…
Explain why a person at a rock concert will not feel gusts of wind coming out of the speakers.
If a meteorite crashed on the moon, would you be able to hear it on Earth? Why, or why not?