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Chapter 21

Chapter 21. The Nature of 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. Components of Sound.

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Chapter 21

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  1. Chapter 21 The Nature of Sound

  2. 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.

  3. Components of Sound • All sounds are created by vibrations. • A vibration is the complete back-and-forth motion of an object or material. • The next slide shows how a stereo speaker produces sound.

  4. Components of Sound: Figure 1

  5. Components of Sound • Sound Waves are longitudinal waves that are caused by vibrations, which are then carried through a substance and transfers energy. • The particles of the substance vibrate back and forth along the path that the sound waves travel. • Sound is transmitted through the vibrations and collisions of the particles.

  6. Components of Sound • Sound waves travel in all directions away from their source. • However, the air or other matter through which the wave is traveling does not travel with the sound waves. • The particles of air only vibrate back and forth.

  7. Components of Sound • All sound waves require a medium (plural, media). • A medium is a substance through which a wave can travel by vibrating particles in the material. • Air is the most common medium of sound waves. • There are no particles to vibrate in a vacuum. • So, no sound can be made in a vacuum.

  8. Components of Sound • Your ears are divided into three regions: the outer, middle, and inner ear. • The outer ear collects sound waves. • Then, organs in the middle ear increase the size of the sound wave’s vibrations. • The inner ear changes the vibrations into electrical signals that your brain interprets as sound.

  9. Components of Sound: Figure 2

  10. Components of Sound • The parts of the ear must work together for you to hear. • If any part of the ear is damaged or does not work properly, hearing loss or deafness may result. • Loud sounds can cause damage the cochlea. • Damage to the cochlea or any other part of the inner ear usually results in permanent hearing loss.

  11. Ch. 21 Sec. 1 Recap • 1) What is a vibration? • 2) Explain how sound is transmitted through particles. • 3) When sound travels through a medium, does the medium travel with the sound? Explain your answer. • 4) What is the most common medium of sound? • 5) Explain how there can be no sound in a vacuum.

  12. Ch. 21 Sec. 1 Recap • 6) List and describe the function of the 3 parts of the ear. • 7) From Figure 2, what is the function of the pinna? • 8) From Figure 2, list the 3 bones that act as levers to increase the size of vibrations. • 9) From Figure 2, what is the eardrum? • 10) From Figure 2, what is the oval window?

  13. Ch. 21 Sec. 1 Recap • 11) What is the function of the liquid in the cochlea? • 12) What 2 things may be caused if part or parts of the ear do not work properly? • 13) What can loud sounds cause damage to? • 14) What does damage to the cochlea result in? • 15) From Figure 1, what is the difference between a compression and rarefaction?

  14. 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. • Explain how amplitude and loudness are related. • Describe how amplitude and frequency can be “seen” on an oscilloscope.

  15. Properties of Sound • The speed of sound depends only on the medium in which the sound is traveling. • How the Speed of Sound Can ChangeSound travels quickly through air, but it travels even faster in liquids and even faster in solids. • Temperature also affects the speed of sound. The cooler the medium is, the slower the speed of sound.

  16. Properties of Sound • How low or high a sound seems to be is the pitch of that sound. The pitch of a sound is related to the frequency of the sound wave. • Frequency and HearingThe frequencies of some sounds are out of the range of human hearing. Sounds that have a frequency too high for people to hear are called ultrasonic.

  17. Properties of Sound: Figure 1

  18. Properties of Sound • 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. • In other words, the sound source of the listener is moving causing the frequency to change. • Changing the frequency affects the properties of the sound.

  19. Properties of Sound: Figure 2

  20. Properties of Sound • The amplitude of a wave is the largest distance the particles in a wave vibrate from their rest positions. • The larger the amplitude, the louder the sound. • The most common unit to express loudness is the decibel (dB).

  21. Properties of Sound • A device called an oscilloscope can graph representations of sound waves, as shown below. Notice that the graphs look like transverse waves rather than longitudinal waves.

  22. Properties of Sound • A microphone attached to an oscilloscope changes a sound wave into an electrical signal. • The electrical signal is graphed on the screen in the form of a wave. • The graph shows the sound as if it were a transverse wave. • So, the sound’s amplitude and frequency are easier to see.

  23. Chapter 21 Sec. 2 Recap • 1)What does the speed of sound depend on? • 2)Rank the speed at which sound travels from 1-3 in solids, liquids, and gases. • 3) What can also affect the speed of sound? • 4) How do cooler temperatures affect the speed of sound? • 5)What property of sound is pitch related to?

  24. Chapter 21 Sec. 2 Recap • 6) What are ultrasonic sounds? • 7) T/F Some sounds have a frequency out of the range of human hearing. • 8) From Figure 1, how do the closeness of air particles relate to high frequency? • 9) From Figure 1, how do the closeness of air particles relate to low frequency? • 10) From Figure 1, how do frequency and pitch relate?

  25. Chapter 21 Sec. 2 Recap • 11) For the Doppler Effect to occur, what changes when the sound source changes locations? • 12) What does altering frequency change? • 13) From Figure 2, what is the sound source? • 14) From Figure 2, what is/are the listeners? • 15) From Figure 2, which listener will hear waves at a higher frequency? • 16) From Figure 2, which listener will hear waves at a lower frequency?

  26. Chapter 21 Sec. 2 Recap • 17) What is amplitude and how does it affect sound? • 18) What is “loudness” expressed in? • 19) What changes a sound wave into an electrical signal on an oscilloscope? • 20) What is the importance of changing the sound wave into an electrical signal and then a visible transverse wave?

  27. 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.

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