2. Longitudinal wave requires a medium (cannot travel in a vacuum such as space)

3. is known as ACOUSTICS ACOUSTICS

4. 2. What causes sound? A sound is a vibration (rapid back and forth motion that creates a longitudinal wave –Remember this wave has compressions and rarefactions

5. –The velocity of speed of sound depends on twos things:the medium it moves through and temperature

6. Solid Liquid Gas Fastest in solids, slowest in gases. Air = 340 m/s water= 1440 m/s steel = 5000 m/s Supersonic: faster than the speed of sound. https://www.youtube.com/watch?v=gWGLA AYdbbc

7. Do molecules move faster or slower as temperature increases? So would sound travel faster or slower as temperature increases? Can affect speed

8. Speeds of Sound at T of 20 C AirAir HeliumHelium HydrogenHydrogen WaterWater Sea waterSea water Iron/SteelIron/Steel GlassGlass AluminumAluminum 343 m/s 1005 m/s 1300 m/s 1440 m/s 1560 m/s ≈5000 m/s ≈ 4500 m/s ≈ 5100 m/s

9. The highness or lowness of sound. Depends on the frequency of sound waves. Everything has it’s own natural frequency High frequency = High pitch Low frequency = Low pitch Note: resonance (amplitude) is the strengthening of sound when combined with frequency

10. Also called LOUDNESS Amount of energy Depends on the amplitude of sound waves. (amplifier) Large Amp. = Loud sound Small Amp. = Soft sound

11.  Near total silence - 0 dB  A whisper - 15 dB  Normal conversation - 60 dB  Lawnmower - 90 dB  Threshold of pain - 120 dB  A rock concert or a jet engine - 120 dB  Gunshot, firecracker - 140 dB  Near total silence - 0 dB  A whisper - 15 dB  Normal conversation - 60 dB  Lawnmower - 90 dB  Threshold of pain - 120 dB  A rock concert or a jet engine - 120 dB  Gunshot, firecracker - 140 dB Measurement of loudness

13. 8a. Normal hearing 20Hz--20 000 Hz Infrasonic 8b. Infrasonic sounds are below our hearing (below 20 Hz) Ultrasonic 8c. Ultrasonic sounds are those above our hearing (above 20,000Hz) (ultrasound) 8d. Sound can damage hearing by damaging the fine hairs that vibrate

14. Sound waves reflecting from hard surfaces but spaced out so it is heard many times over long distances

15. Sound waves reflecting from hard surfaces but faster or closer together Ex.: Multiple echo resulting from the direct sound AND the reflected sound

16. Reverberation vs Echo Animations courtesy of Paul Hewitt and borrowed from physicsclassroom.com

17. Sound is a pressure wave Animations courtesy of Paul Hewitt and borrowed from physicsclassroom.com

18. Tuning fork creating a sound wave Animations courtesy of Paul Hewitt and borrowed from physicsclassroom.com

19. Guitar String creating a sound wave Animations courtesy of Paul Hewitt and borrowed from physicsclassroom.com

20. Ultrasound can be used to create internal images of the human body –Ex. Pregnant woman gets a “picture” of her unborn baby

21. An equal mixture of all frequencies of soundAn equal mixture of all frequencies of sound Used to calm stressUsed to calm stress Used in office buildingsUsed in office buildings

22. Yep! There is such a thingYep! There is such a thing Causes:Causes: –Damage to ear resulting in hearing loss –Stress

23. Caused by destructive interferenceCaused by destructive interference Result – hardly any or no soundResult – hardly any or no sound Bad for concert halls – designers be careful!Bad for concert halls – designers be careful!

24. use of sound waves to interpret echoes for location of landforms, prey, etc. by bats, dolphins, submarines (SONAR), etc.

25. Change in pitch due to motion. Moving towards increases the pitch Moving away decreases the pitch https://i1.ytimg.com/vi/-wy5oX0AXv8/mqdefault.jpg