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What is sound? define, define, define!

What is sound? define, define, define!. Changes in air pressure Perception of the changes We can hear from about 15 changes per second to 20000 changes per second (Hz).

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What is sound? define, define, define!

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  1. What is sound?define, define, define! • Changes in air pressure • Perception of the changes We can hear from about 15 changes per second to 20000 changes per second (Hz)

  2. “If a tree falls in a forest far from any sound detector (human ear, microphone, etc.), does the tree's fall make any noise?”

  3. Know thy “enemy”

  4. Did you know? Changes in air pressure perceived as sound are the same as…

  5. Did you know? Changes in air pressure perceived as sound are the same as… …changes in air pressure discussed in meteorology

  6. Did you know? Changes in air pressure perceived as sound are the same as… …changes in air pressure discussed in meteorology Difference? Weather – greater magnitude, and change far more slowly

  7. So many waves, but which is the one… Nice animated examples: http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/waves/u10l1c.html

  8. Sound - longitudinal

  9. Sound vibrations, vibrations, vibrations

  10. Sound simple harmonic motion

  11. Simple harmonic motion • Vibrating system • Common property: motion repetitive

  12. Simple harmonic motion 1.Period – time between two repetitions (duration of one cycle) 2.Wavelength – the distance between corresponding points, from cycle to cycle as the wave repeats itself 3. Frequency – how often the wave repeats itself during time unit 4. Amplitude – how high and low wave oscillations are 5. Phase – position of a wave at a certain time

  13. Refractionwave bends(refracts) around the object • Obstacle size: smaller than a wavelength

  14. Reflectionthe wave reflects away from the object • Obstacle dimensions significantly larger than wavelength • any change in the medium

  15. Reflectionon a string

  16. Reflectionwithin a tube

  17. Superpositionwaves in a crowd

  18. Standing waves

  19. STRINGbound at both ends

  20. Tubeclosed at both ends

  21. Tubeopened at both ends

  22. Tubeclosed at one ends

  23. Velocity and pressure

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