1. Sound Waves

2. Mechanical Waves
Mechanical Waves – waves that need a medium to transport energy and travel through
EX: Sound, Water, Seismic

3. Acoustic Waves Acoustic Waves – also known as sound waves
Vacuum – empty space where mechanical waves cannot travel

4. Interacting Particles
In a sound wave, air particles interact with each other
In a slinky wave, coils interact with each other
In a stadium wave, the fans interact with each other

5. More dense = Faster speed
Speed of Sound
Medium
Speed
Solid
Fast
Liquid
Gas (Air)
Slow
Vacuum
None
More dense = Faster speed

6. Speed of Sound As air temperature ↑, the speed of sound ↑

7. Pitch
Pitch – how high or low a sound seems to be –generated by the frequency of the wave

8. Amplitude
Amplitude – loudness of the sound (volume control)

9. How Sound is Created
Sound (human voice) is created by the vibrations in the vocal cords
Human Audio Frequency

10. Doppler Effect
Doppler Effect – the change in frequency and wavelength due to the motion of the source

11. Doppler Effect
Imagine a bug jiggling its legs and bobbing up and down in the middle of a quiet puddle
If the bug bobs in the water at a constant frequency, the wavelength will be the same for all successive waves
The wave frequency is the same as the bug’s bobbing frequency

12. Doppler Effect
Each wave crest has a shorter distance to travel so they arrive more frequently
The bug maintains the same bobbing frequency as before
However, an observer at B would encounter a higher frequency if the bug is moving toward the observer
Each crest has to travel farther than the one ahead of it due to the bug’s motion

13. Faster because it’s a liquid compared to a gas
Question
Is the speed of sound faster or slower in water compared to its speed in air?
Faster because it’s a liquid compared to a gas