1. How to Use This Presentation To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show”, or simply press F5 on the top row of your keyboard. To advance to the next slide click the left mouse button once. From the Chapter screen you can click on any section to go directly to that section’s presentation. Blank or “missing” areas of a slide will remain hidden until the left mouse button is clicked. You may exit the slide show at any time by pressing the Esc key Copyright © by Holt, Rinehart and Winston. All rights reserved.

2. The Nature of Sound Module N: Chapter 2 Section 1: What Is Sound? Section 2: Properties of Sound Section 3: Interactions of Sound Waves Section 4: Sound Quality Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

3. What Is Sound? Section 1 Bellringer If you’ve ever been near a large fireworks display, you may have felt the sound of the explosions. Think of other instances when you might feel sound and describe them in your science journal. Copyright © by Holt, Rinehart and Winston. All rights reserved.

4. What Is Sound? Section 1 Objectives Describe how vibrations cause sound. Explain how sound is transmitted through a medium. Explain how the human ear works, and identify its parts. Identify ways to protect your hearing. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

5. What Is Sound? Section 1 Sound and Vibrations Sound Waves A sound wave is a longitudinal wave caused by vibrations and carried through a substance. Sound waves coming from a speaker are shown on the next slide. Sound and Media Another characteristic of sound is that all sound waves require a medium (plural, media). A medium is a substance through which a wave can travel. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

6. Sounds from a Stereo Speaker Section 1 Copyright © by Holt, Rinehart and Winston. All rights reserved.

7. What Is Sound? Section 1 How You Detect Sound Hearing Electrical Signals Your ears change sound waves into electrical signals that allow you to hear. Making Sounds Versus Hearing Sounds Have you heard this riddle? If a tree falls in the forest and no one is around to hear it, does the tree make a sound? When a tree falls and hits the ground, the tree and the ground vibrate. These vibrations make compressions and rarefactions in the surrounding air. So, there would be a sound! Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

8. What Is Sound? Section 1 Hearing Loss and Deafness All the Components of the Ear Are Important to Hearing The many parts of the ear must work together for you to hear sounds. If any part of the ear is damaged or does not work properly, hearing loss or deafness may result. Protecting Your Hearing Loud sounds can be blocked out by earplugs. You can listen at a lower volume when you are using headphones. You can also move away from loud sounds. If you are near a speaker playing loud music, just move away from it. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

9. Properties of Sound Section 2 Bellringer You are the commander of a space station located about halfway between Earth and the moon. You are in the Command Center, and your chief of security tells you that sensors have just detected an explosion 61.054 km from the station. How long will it be before you hear the sound of the explosion? Record your answer in your science journal, and then share your answers with the group. Copyright © by Holt, Rinehart and Winston. All rights reserved.

10. Properties of Sound Section 2 Objectives Compare the speed of sound in different media. Explain how frequency and pitch are related. Describe the Doppler effect, and give examples of it. Explain how amplitude and loudness are related. Describe how amplitude and frequency can be “seen”on an oscilloscope. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

11. Properties of Sound Section 2 The Speed of Sound Copyright © by Holt, Rinehart and Winston. All rights reserved. The Speed Depends on the Medium The speed of sound depends only on the medium in which the sound is traveling. How the Speed of Sound Can Change Sound travels quickly through air, but it travels even faster in liquids and even faster in solids. Temperature also affects the speed of sound. In general, the cooler the medium is, the slower the speed of sound. End of Slide

12. Properties of Sound Section 2 Pitch and Frequency How low or high a sound seems to be is the pitch of that sound. The frequency of a wave is the number of crests or troughs that are made in a given time. The relationship between pitch and frequency is shown on the next slide. Sounds that have a frequency too high for people to hear are called ultrasonic. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

13. Frequency and Pitch Section 2 Copyright © by Holt, Rinehart and Winston. All rights reserved.

14. Properties of Sound Section 2 Pitch and Frequency, continued The Doppler Effect is the apparent change in the frequency of a sound caused by the motion of either the listener or the source of the sound. The next slide shows how the Doppler effect works. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

15. The Doppler Effect Section 2 Copyright © by Holt, Rinehart and Winston. All rights reserved.

16. Properties of Sound Section 2 Loudness and Amplitude Energy and Vibrations An increase in sound energy causes air particles to vibrate farther from their rest positions. Increasing Amplitude The larger the amplitude, the louder the sound. Measuring Loudness The most common unit used to express loudness is the decibel (dB). Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

17. Properties of Sound Section 2 “Seeing” Amplitude and Frequency Oscilloscope A device called an oscilloscope is used to graph representations of sound waves. From Sound to Electrical Signal A microphone is attached to the oscilloscope and changes a sound wave into an electrical signal. The electrical signal is graphed on the screen in the form of a wave. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

18. Interactions of Sound Waves Section 3 Bellringer Answer the following questions in your science journal: On an oscilloscope, does a wave with a larger amplitude (greater crests and troughs) indicate louder sound or higher pitch? As frequency increases, does pitch get higher or lower? What is the speed of sound dependent on? What do you think happens when two sound waves interact with each other? Copyright © by Holt, Rinehart and Winston. All rights reserved.

19. Interactions of Sound Waves Section 3 Objectives Explain how echoes are made, and describe their use in locating objects. List examples of constructive and destructive interference of sound waves. Explain what resonance is. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

20. Interactions of Sound Waves Section 3 Reflection of Sound Waves Copyright © by Holt, Rinehart and Winston. All rights reserved. Echolocation The use of reflected sound waves to find objects is called echolocation. Bats use echolocation, as illustrated on the next slide. End of Slide

21. Echolocation Section 3 Copyright © by Holt, Rinehart and Winston. All rights reserved.

22. Interactions of Sound Waves Section 3 Reflection of Sound Waves, continued Copyright © by Holt, Rinehart and Winston. All rights reserved. Echolocation Technology People use echoes to locate objects underwater by using sonar. Sonar is a type of electronic echolocation. The next slide illustrates how sonar works. Ultrasonography is a medical procedure that uses echoes to “see” inside a patient’s body without doing surgery. End of Slide

23. How Sonar Works Section 3 Copyright © by Holt, Rinehart and Winston. All rights reserved.

24. Interactions of Sound Waves Section 3 Interference of Sound Waves Copyright © by Holt, Rinehart and Winston. All rights reserved. Interference and the Sound Barrier As the source of a sound—such as a jet plane—gets close to the speed of sound, the sound waves in front of the jet plane get closer and closer together. The result is constructive interference. Interference and Standing Waves A standing wave is a pattern of vibration that looks like a wave that is standing still. Waves and reflected waves are going through the string. Where you see maximum amplitude, waves are interfering constructively. Where the string seems to be standing still, waves are interfering destructively. End of Slide

25. Interactions of Sound Waves Section 3 Resonance Copyright © by Holt, Rinehart and Winston. All rights reserved. What Is Resonance? Resonance happens when an object vibrating at or near a resonant frequency of a second object causes the second object to vibrate. Resonance in Musical Instruments Musical instruments use resonance to make sound. End of Slide

26. Sound Quality Section 4 Bellringer Answer the following questions in your science journal then share your responses with the group: Which strings on a piano have lower pitch? Why does a tuba have a lower pitch than a trumpet? Why are some sounds pleasing to hear and others are not? Explain your answer. Copyright © by Holt, Rinehart and Winston. All rights reserved.

27. Sound Quality Section 4 Objectives Copyright © by Holt, Rinehart and Winston. All rights reserved. Explain why different instruments have different sound qualities. Describe how each family of musical instruments produces sound. Explain how noise is different from music. End of Slide

28. Sound Quality Section 4 What Is Sound Quality? Copyright © by Holt, Rinehart and Winston. All rights reserved. A Mixing of Pitches The result of several pitches mixing together through interference is sound quality. End of Slide

29. Sound Quality Section 4 Sound Quality of Instruments String Instruments Violins, guitars, and banjos are examples of string instruments. They make sound when their strings vibrate after being plucked or bowed. Wind Instruments A wind instrument produces sound when a vibration is created at one end of its air column. Wind instruments are sometimes divided into two groups— woodwinds and brass. Percussion Instruments Drums, bells, and cymbals are percussion instruments. They make sound when struck. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

30. Sound Quality Section 4 Music or Noise What Is Noise? Noise can be described as any sound, especially a nonmusical sound, that is a random mix of frequencies (or pitches). Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

31. The Nature of Sound Chapter 21 Concept Map Copyright © by Holt, Rinehart and Winston. All rights reserved. Use the following terms to complete the concept map on the next slide: loudness, oscilloscope, frequency, sound, interference, pitch, medium.

32. Concept Map Chapter 21 Copyright © by Holt, Rinehart and Winston. All rights reserved.

33. Concept Map Chapter 21 Copyright © by Holt, Rinehart and Winston. All rights reserved.