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Perceiving Sound

Perceiving Sound. Before we start!. A review of Light. Light vs. Sound. What do you think is going to happen? . Make a prediction. What will happen when air is removed from the bell jar? Don’t forget to explain why. . Make Observations. Why did this happen? . Sound is… .

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Perceiving Sound

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  1. Perceiving Sound

  2. Before we start! • A review of Light

  3. Light vs. Sound

  4. What do you think is going to happen? • Make a prediction. • What will happen when air is removed from the bell jar? • Don’t forget to explain why.

  5. Make Observations

  6. Why did this happen?

  7. Sound is… • A mechanical wave. • Longitudinal wave. • Produced by the vibration of an object and transmitted to the object’s environment. • Requires a medium.

  8. The speed of Sound • It changes from one medium to another.

  9. Why is that? • Using the particle model to justify your answer. Why does sound travel faster in solids than in gases?

  10. The Decibel (Db) • The unit of measurement for the intensity of sound. • High Intensity sound = High amplitude = More Decibels. • Low Intensity sound = Low amplitude = Low Decibels.

  11. The Decibel Scale • All decibel measurements are not completely accurate, they are related to our perception by the human ear. • A sound measuring 0 Db is can barely be heard by the ear. • We measure variations on the scale by a factor of 10.

  12. A Sample of a Decibel Scale Another one can be found on p. 103 of your textbook.

  13. Try some Questions • P. 118 # 8- 10

  14. Pitch and Frequency • Lower Pitch = lower frequency sound. • High Pitch = Higher frequency sound.

  15. Infrasound and Ultrasounds • Infrasounds = sounds under 20Hz • Used by some animals to communicate. • E.g. Elephants • Ultrasounds = sounds above 20 000 Hz • Used in medical imaging • Used by some animals like bats (echolocation)

  16. Can we hear all frequencies?

  17. What happens when you age? • http://www.youtube.com/watch?v=qNf9nzvnd1k • http://www.youtube.com/watch?v=VxcbppCX6Rk

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