1. SOUND
Video Clip
intro

2. 1) Recognize that all waves transfer energy.
2) Explain the Doppler Effect in terms of everyday interactions.
5) Compare and contrast the characteristics of electromagnetic and mechanical (sound)
waves.
3) Relate frequency & wavelength to the energy of different types of electromagnetic waves & mechanical waves.
6) Explain the phenomena of reflection, refraction, interference, & diffraction.
4) Relate the speed of sound to different mediums. 2

3. Remember: Waves transport ENERGY

4. Sound Waves Sound Waves are Compressional waves.
The vibrations of the molecules are parallel to the direction of the wave.
Produced by the compressions and rarefaction of matter.

5. Sound Wave Propagation
Sound is produced by a vibrating object.
As one individual particle is disturbed, it transmits the disturbance to the next interconnected particle.
This disturbance continues to be passed on to the next particle.
The result is that energy is transported without the actual transport of matter.
Clip

7. Review Clip

8. How We
Hear

9. Compressions are high density areas, and rarefactions are low density areas.

10. When a sound wave reaches the ear, a series of high and low pressure regions hit the eardrum.
The arrival of a compression or high pressure region pushes the eardrum inward; the arrival of a low pressure regions serves to “pull” the eardrum outward.
The continuous arrival of high and low pressure regions sets the eardrum into motion.
Eardrum
Video Clip

12. Pitch
Pitch is the highness or lowness of a sound.
Clip

13. Sound Activity

14. Frequency and Pitch
The frequency of a sound wave determines the pitch.
Pitch is the highness or lowness of a sound.
The higher the frequency…the higher the pitch.
Clip

15. Simulation (test tubes in lab activity examples)

16. Sound waves below 20 Hz are called infrasonic.
Low Pitch
High Pitch
Sound waves below 20 Hz are called infrasonic.
Sounds waves above 20,000 Hz are called ultrasonic.
Range of Human Hearing is from about Hz –20,000 Hz
Review Clip

17. Bioacoustics
is a branch of science concerned with the production of sound and its effects on living systems.
Animals that generate “infrasound” include elephants, whales, alligators, hippos, rhinos, giraffe, lions, tigers and several birds. (whale)
Animals that generate “ultrasound” include Dolphins, bats, many birds and insects.

18. Echolocation Bats send out sound waves using their mouth or nose.
When the sound hits an object an echo comes back.
They can the distance between themselves and the object  
They can identify an object by the sound of the echo.
They can even tell the size, shape and texture of  a tiny insect from its echo.  
Most bats use echolocation to navigate in the dark and find food. VIDEO
Echolocation

19. Animal Communication With Sound

20. Sonar

21. Speed of Sound
Speed depends upon how fast one particle can transfer its motion to another particle.
Remember: Sound waves are mechanical waves.
Speed of sound depends on the
medium
Temperature
Why?

22. What is the Speed of Sound?
Video Clip

24. In which situation will the sound travel the fastest?...slowest?

25. In which material will the sound travel the fastest?...slowest?

26. What is causing this change?

27. Loudness
Depends on the amplitude. Larger amplitude means more pressure.
Remember: amplitude is measure of the amount of energy in the wave.
Sound level is measured in Decibels.

28. Which sound wave would be the loudest?

29. The energy transported by a wave is directly proportional to the square of the amplitude of the wave.

31. Common Sounds in Decibels
Decibel Level
Listener's Perception
Whisper 10
Barely Audible
Quiet Conversation 30
Faintly Heard
Average Office 50
Moderate Level
Summer Nocturnal Insects 60
Noisy Office 70
Loud
Average Street Traffic 85
Very Loud
Jackhammer
100
Extremely Loud
Jet Aircraft Taking Off
120
Physical Pain

33. All sound consists of a waves.
If you add 2 waves together that are going in the same direction, and if those waves are in phase--that is, the peaks and valleys of the waves line up--then the amplitude or height of the waves will double.
Constructive Interference

34. Destructive Interference
If you add 2 waves that are going in the same direction, and if those waves are completely out of phase--that is, the peaks of one line up with the valleys of the other--then the amplitude or height of the waves cancel each other out.
Waves out of phase will cancel each other
Destructive Interference

35. Video Clip

37. Reflection of sound waves Echo vs. Reverberation
Sound waves can be reflected
A reverberation is perceived when the reflected sound wave reaches your ear in less than 0.1 second after the original sound wave.

38. Tacoma Narrows Bridge Collapse
(Nov.7th 1940)
Galloping Gertie
On a day of rather high winds, Gertie took on a 30-hertz transverse vibration (like sending waves down a rope by moving the end up and down) with an amplitude of 1½ feet! It later took on a twisting motion of about 14 hertz and quickly tore itself in two.

39. What’s causing the change in pitch?

40. Doppler Effect
Variation in the perceived pitch of a sound due to a moving sound source.
“bunches up “ in front of the source
Spreads out behind the source

41. simulation

42. Website
Web Site

43. Sonic Boom
a "sonic boom" is the sudden onset and release of pressure after the buildup by the shock wave
Example

45. Click on the Picture

46. This picture shows a sonic boom created by the THRUST SSC team car as it broke the land speed record (and also broke the sound barrier on land).

47. Sound Waves Review

49. Review

50. “What’s wrong (or right) with these movies?”

51. Thanks to: http://asa.aip.org/ http://www.animalvoice.com/Links.htm