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Sound

Sound. Longitudinal wave requires a medium (cannot travel in a vacuum such as space). 1. Study of Sound. is known as ACOUSTICS. 2. What causes sound?. A sound is a vibration (rapid back and forth motion that creates a longitudinal wave

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Sound

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  1. Sound • Longitudinal wave • requires a medium • (cannot travel in a vacuum such as space)

  2. 1. Study of Sound is known as ACOUSTICS

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

  4. 3. Speed of sound • The velocity of speed of sound depends on twos things:the medium it moves through and temperature

  5. 3a.Type of Medium 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=gWGLAAYdbbc

  6. 3b. Temperature Can affect speed Do molecules move faster or slower as temperature increases? So would sound travel faster or slower as temperature increases?

  7. Air Helium Hydrogen Water Sea water Iron/Steel Glass Aluminum 343 m/s 1005 m/s 1300 m/s 1440 m/s 1560 m/s ≈5000 m/s ≈ 4500 m/s ≈ 5100 m/s Speeds of Sound at T of 20 C

  8. 4. Pitch 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

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

  10. 5a. Decibels Measurement of loudness • 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

  11. 6. Ear

  12. 8a. Normal hearing 20Hz--20 000 Hz 8b. Infrasonicsounds are below our hearing (below 20 Hz) 8c. Ultrasonicsounds are those above our hearing (above 20,000Hz) (ultrasound) 8d. Sound can damage hearing by damaging the fine hairs that vibrate

  13. 7. Echo • Sound waves reflecting from hard surfaces but spaced out so it is heard many times over long distances

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

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

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

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

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

  19. 9. Sound Extras • Ultrasound can be used to create internal images of the human body • Ex. Pregnant woman gets a “picture” of her unborn baby

  20. White Noise • An equal mixture of all frequencies of sound • Used to calm stress • Used in office buildings

  21. Noise Pollution • Yep! There is such a thing • Causes: • Damage to ear resulting in hearing loss • Stress

  22. Dead Spots • Caused by destructive interference • Result – hardly any or no sound • Bad for concert halls – designers be careful!

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

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

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