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

3. is known as ACOUSTICS

4. Properties of Sound A sound is a vibration Pressure wave – longitudinal Frequency = pitch v = 334 m/s in air at room temperature Velocity is dependent upon the material

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

6. Waves travel fastest in solids, slowest in gases. Solid Liquid Gas

7. 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.

8. Sound travels faster in warm water than in cold water By measuring the time it takes for sound to travel a known distance through the ocean the average temperature of the water can be calculated = ATOC (acoustic thermometry of ocean climate)

9. Speeds of Sound at T = 20 C (room temperature) 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

10. The highness or lowness of sound. Depends on the frequency of sound waves. High frequency = High pitch Low frequency = Low pitch

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

12. Some Intensities (in dB) loudness measured in decibels Jet plane at 30 mJet plane at 30 m Threshold of painThreshold of pain Indoor rock concertIndoor rock concert Auto interiorAuto interior Street trafficStreet traffic ConversationConversation WhisperWhisper Rustle of leavesRustle of leaves 140 120 75 70 65 1x10 -10 1x10 -11

13. Sound waves reflecting from hard surfaces Ex.: Multiple echo resulting from the direct sound AND the reflected sound

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

15.  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

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

17. Ear

18. Human Ear 20Hz--20 000 Hz Infrasonic: Infrasonic: below 20 Hz (below our hearing) Ultrasonic Sound: above 20,000Hz (above our hearing)

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

20. Ultrasounds 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. Used to locate underwater objects and distances. ***Reflection**

25. Change in pitch due to motion.

28. *Moving towards increases the pitch *Moving away decreases the pitch *Think of sirens

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