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. Speed of Sound MediumSpeed SolidFast LiquidMedium Gas (Air)Slow VacuumNone More dense = Faster speed

6. Speed of Sound As air temperature ↑, the 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 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 Each wave crest has a shorter distance to travel so they arrive more frequently

13. 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