1. Table of Contents The Nature of Sound Properties of Sound Music
How You Hear Sound
Using Sound

2. Sound Waves - The Nature of Sound
Sound is a disturbance that travels through a medium as a longitudinal wave. As a gong vibrates, it creates sound waves that travel through the air.

3. Interactions of Sound Waves
- The Nature of Sound
Interactions of Sound Waves
Sound waves reflect off objects, diffract through narrow openings and around barriers, and interfere with each other.
Diffraction

4. Speed of Sound
The speed of sound in air is approximately 344 m/s, whereas the speed of light is about 300,000,000 m/s.
This is why we hear the crack of the bat after we see the ball hit or thunder after lightning.

5. The Speed of Sound - The Nature of Sound
The speed of sound depends on the elasticity, density, and temperature of the medium the sound travels through.

6. Temperature and the Speed of Sound
- The Nature of Sound
Temperature and the Speed of Sound
The speed of sound in dry air changes as the temperature changes. The graph shows data for the speed of sound in air at temperatures from –10ºC to 20ºC.

7. Temperature and the Speed of Sound
- The Nature of Sound
Temperature and the Speed of Sound
Reading Graphs:
What is the speed of sound in air at –10ºC?
The speed at –10ºC is 325 m/s.

8. Temperature and the Speed of Sound
- The Nature of Sound
Temperature and the Speed of Sound
Interpreting Data:
Does the speed of sound increase or decrease as temperature increases?
The speed of sound increases as air temperature increases.

9. Temperature and the Speed of Sound
- The Nature of Sound
Temperature and the Speed of Sound
Predicting:
What might be the speed of sound at 30ºC?
At 30ºC, the speed of sound might be 349 m/s.

10. Elasticity - The Nature of Sound
Elasticity is the ability of a material to bounce back after being disturbed. You can model elasticity by representing the particles in a medium as being held together by springs.

11. Density - The Nature of Sound
Density is how much mass there is in a give volume. The volumes of the cubes are the same, but the brass has more mass.

12. Identifying Main Ideas
- The Nature of Sound
Identifying Main Ideas
As you read the section “Interactions of Sound Waves,” write the main idea–the biggest or most important idea–in a graphic organizer like the one below. Then write three supporting details that further explain the main idea.
Main Idea
Sound waves interact with objects and with other sound waves.
Detail
Detail
Detail
Reflection occurs when sound waves strike a surface.
Sound waves can diffract around corners and through openings.
The interference of sound waves can be constructive or destructive.

13. Click the SciLinks button for links on sound.
- The Nature of Sound
Links on Sound
Click the SciLinks button for links on sound.

14. Click the Video button to watch a movie about the speed of sound.
- The Nature of Sound
Speed of Sound
Click the Video button to watch a movie about the speed of sound.

15. End of Section: The Nature of Sound

16. Loudness - Properties of Sound
The loudness of different sounds is compared using a unit called the decibel (dB).

17. What can hurt your ears
A typical conversation occurs at 60 dB – not loud enough to cause damage. A bulldozer that is idling (note that this is idling, not actively bulldozing) is loud enough at 85 dB that it can cause permanent damage after only 1 work day (8 hours). When listening to a personal music system with stock earphones at a maximum volume, the sound generated can reach a level of over 100 dBA, loud enough to begin causing permanent damage after just 15 minutes per day! A clap of thunder from a nearby storm (120 dB) or a gunshot ( dB, depending on weapon), can both cause immediate damage.

18. Pitch - Properties of Sound
The pitch of a sound that you hear depends on the frequency of the sound wave.

19. Pitch
If a sound source moves towards a listener, what happens to the pitch?
Goes up and down repeatedly
Decreases
Increases
Stays the same

20. Pitch - Properties of Sound
Link to website with frequencies that kids vs. adults can hear.

21. Changing Pitch - Properties of Sound
When you sing, you change pitch using your vocal cords. Your vocal cords are located in your voice box, or larynx.

22. The Doppler Effect - Properties of Sound
The change in frequency of a wave as its source moves in relation to an observer is called the Doppler effect. When a sound source moves, the frequency of the waves changes because the motion of the source adds to the motion of the waves.
Moving police car link
Cool link!

23. The Doppler Effect - Properties of Sound
When the plane travels almost as fast as the speed of sound, the sound waves pile up in front of the plane. This pile up is the “sound barrier.”
Link to applet for Doppler effect

24. Resonance Copy and paste URL to view resonance
Tacoma Narrows bridge collapse

25. Outlining - Properties of Sound
An outline shows the relationship between main ideas and supporting ideas. As you read, make an outline about the properties of sound. Use the red headings for the main ideas and the blue headings for the supporting ideas.
Loudness
Energy of a Sound Source
Distance From a Sound Source
Measuring Loudness
Pitch
Pitch and Frequency
Changing Pitch
Doppler Effect
What Causes the Doppler Effect?
What Causes Shock Waves?

26. More on the Properties of Sound
Click the PHSchool.com button for an activity about the properties of sound.

27. Click the Video button to watch a movie about pitch.
- Properties of Sound
Pitch
Click the Video button to watch a movie about pitch.

28. End of Section: Properties of Sound

29. - Music
Sound Quality
The sound quality of musical instruments results from blending a fundamental tone with its overtones. Resonance also plays a role in sound quality.

30. Groups of Musical Instruments
There are three basic groups of musical instruments: stringed instruments, wind instruments, and percussion instruments.

31. Musical Instruments Activity
Click the Active Art button to open a browser window and access Active Art about musical instruments.

32. Previewing Visuals - Music
When you preview, you look ahead at the material to be read. Preview Figure 15. Then write two questions that you have about the diagram in a graphic organizer like the one below. As you read, answer your questions.
Musical Instruments
Q. How is pitch changed in each type of instrument?
A. By changing the frequency of the vibrations
Q. How is the loudness changed in each type of instrument?
A. By changing the energy of the vibrations

33. End of Section: Music

34. The Human Ear - How You Hear Sound
The outer ear funnels sound waves, the middle ear transmits the waves inward, and the inner ear transforms sound waves into a form that travels to your brain.

35. Sequencing - How You Hear Sound
Sequence is the order in which the steps in a process occur. As you read, make a flowchart that shows how you hear sound. Put the steps of the process in separate boxes in the order in which they occur.
How You Hear Sound
The outer ear funnels sound waves into the ear canal.
Sound waves make the eardrum vibrate.
Tiny bones in the middle ear transmit vibrations to the inner ear.
Vibrations in the cochlea of the inner ear send messages to the brain.

36. End of Section: How You Hear Sound

37. Echolocation - Using Sound
Some animals, including bats and dolphins, use echolocation to navigate and to find food.

38. - Using Sound
Sonar
A sonar device sends out ultrasound waves and then detects the reflected waves.

39. Calculations
Suppose that the sound waves of a sonar device on the ship are sent down and reflected back up by the sunken ship. If it takes 5 seconds from the waves to travel from their source to the sunken ship and back, what is the depth of the sunken ship (speed of sound: 1,520 m/s): Answer: 3800m

40. Sonograms/Ultrasounds
- Using Sound
Sonograms/Ultrasounds
An ultrasound exam is a procedure that uses high-frequency sound waves to scan a woman’s abdomen and pelvic cavity, creating a picture (sonogram) of the baby and placenta. Although the terms ultrasound and sonogram are technically different, they are used interchangeably and reference the same exam.

41. Sonograms/Ultrasounds
- Using Sound
Sonograms/Ultrasounds
Ultrasound testing can also be used to diagnosis other medical ailments.
blockages
kidney stones
Ultrasound is used for
Cleaning
Disintergrating bacteria

42. Comparing and Contrasting
- Using Sound
Comparing and Contrasting
As you read, compare and contrast echolocation and sonar by completing a table like the one below.
Using Sound
Feature
Echolocation
Sonar
Type of wave
Ultrasound
Ultrasound
Medium(s)
Air, water
Water
Find water depth, sunken objects,
schools of fish
Purposes
Navigate, find food

43. Click the PHSchool.com button for an activity about sonar.
- Using Sound
More on Sonar
Click the PHSchool.com button for an activity about sonar.

44. End of Section: Using Sound

45. Graphic Organizer Sound Longitudinal waves Intensity Frequency
travels as
has properties
Longitudinal waves
Intensity
Frequency
speed depends on
is heard as
is heard as
Elasticity
Density
Temperature
Loudness
Pitch

46. End of Section: Graphic Organizer