1. Sound
Waves we can hear

2. Where Does Sound Come From?
The source of all sound waves is
Vibration

3. Sound Examples Strings in instruments Drumhead in drum
Vocal chords in your throat
Opening and closing a door

4. How Vibration Makes Sound
The vibration sets the surrounding air molecules in motion
The frequency of a sound wave is the same frequency as the vibrating source
Sound travels as a longitudinal wave through the air to your ear

5. Anatomy of a Longitudinal Wave
Wavelength
Compression
Rarefaction
Wave Motion

6. Sound Vocabulary Wavelength: Distance between two compressions
Frequency (vibrations per second)
Perceived as PITCH
Low Frequency = low pitch
High Frequency = high pitch
Amplitude: Perceived as LOUDNESS
Large amplitude = loud sound
Small amplitude = soft sound

7. Name That Sound Loud & high-pitched Loud & low-pitched
Soft & low-pitched
Medium-loud and medium-pitched
Loud & low-pitched
Soft & high-pitched
Medium-loud and high-pitched

8. Name That Sound Loud & high-pitched F Loud & low-pitched E
Soft & low-pitched D
Medium-loud and medium-pitched A
Loud & low-pitched E
Soft & high-pitched B
Medium-loud and high-pitched C

9. Transmitting Sound Sound can only travel through matter SOLID –
Putting your ear to a door or wall
(better if you use a glass)
LIQUIDS –
Dolphins communicating in water
GAS –
Talking

10. What‘s Wrong with This?
Rumble, rumble, rumble

11. What‘s Wrong with This? There’s no sound in space!
Rumble, rumble, rumble
There’s no sound in space!
Sound cannot travel in a vacuum where there is no matter

12. Speed of Sound Speed of Sound at room temperature
340 m/s
Light travels at 300,000,000 m/s
Sound is a million times slower than light
Speed depends on the temperature and elasticity of the medium
Elasticity
Ability to change shape then return to initial shape quickly
Steel is elastic
Putty is inelastic

13. Speed of Sound
Atoms in elastic materials are relatively close together and respond quickly to each other’s motion

14. Speed of Sound Sound travels fastest in : Examples:
SOLID  LIQUID  GASES
Examples:
Sound in steel 15 times faster than air
Sound in water 4 times faster than air

15. Speed of Sound
Example
If you put your ear to the ground you can hear distant horses before you could hear them through the air

16. Speed of Sound Speed of sound INCREASES as temperature INCREASES
Molecules moving faster bump into each other more often.
Amplitude (Loudness) and frequency (Pitch) DO NOT affect speed of sound
Sonic Booms
Occur when objects travels as fast as the speed of sound.