17.4 Key Concepts What properties explain the behavior of sound? How is ultrasound used?

1. 17.4 Key Concepts • What properties explain the behavior of sound? • How is ultrasound used? • How does frequency of sound change for a moving source? • What are the functions of the three main regions of the ear? • How is sound recorded? • How do musical instruments vary pitch?

2. You can identify sounds without seeing them because sound waves carry information to your ______. People who work in places where sound is very loud need to ____________ their hearing. ears protect

3. Properties of Sound Waves • Many behaviors of sound can be explained using a few properties— • __________________ • __________________ • __________________ • __________________ • __________________ speed Intensity loudness frequency pitch

4. Properties of Sound Waves longitudinal Sound waves are ________________ waves—compressions and rarefactions that travel through a medium.

5. Properties of Sound Waves Speed It takes __________ for sound to travel from place to place. The speed of sound ___________ in different media. In dry air at 20°C, the speed of sound is 342 meters per second. time varies

6. Properties of Sound Waves

7. Properties of Sound Waves In general, sound waves travel fastest in ____________, slower in liquids, and slowest in gases. • Particles in a solid tend to be ____________ together than particles in a liquid or a gas. • The speed of sound depends on many factors, including the _______________ of the medium and how _________________ the medium is. solids closer density elastic

8. Properties of Sound Waves Intensity and Loudness Intensity is the ___________ at which a wave’s energy flows through a given area. • Sound intensity depends on both the wave’s ______________ and the ______________ from the sound source. • The __________________(dB) is a unit that compares the intensity of different sounds. rate distance amplitude decibel

9. Properties of Sound Waves For every 10-decibel increase, the sound intensity increases ______________ • A 0-decibel sound can just barely be heard. • A 20-decibel sound has ______ times more energy per second than a 0-decibel sound. • A 30-decibel sound delivers _______ times more energy per second than a 0-decibel sound. tenfold 100 1000

10. Properties of Sound Waves Lengthy exposure to sounds more intense than ______decibels can cause hearing damage. 90

11. Properties of Sound Waves physical response Loudness is a ____________ __________ to the intensity of sound, modified by physical factors. • The loudness depends on sound _____________. • Loudness also depends on factors such as the ______________ of your ears and how your ________________ interprets sound waves. intensity health brain

12. Properties of Sound Waves Frequency and Pitch The frequency of a sound wave depends on how _______ the source of the sound is __________________. The air in the tubing of brass instruments forms a _____________ wave. Longer tubing makes a standing wave with a ______________ wavelength and a _______ frequency. fast vibrating standing larger lower

13. Properties of Sound Waves The French horn can produce lower notes than the trumpet because it can make a _________ tube for a standing wave. longer Trumpet French Horn

14. Properties of Sound Waves Pitch is the frequency of a sound as you _______________ it. • High-frequency sounds have a ________ pitch, and low-frequency sounds have a _______ pitch. • Pitch also depends on other factors such as your _______ and the _____________ of your ears. perceive high low age health

15. Ultrasound Ultrasound is used in a variety of applications, including ______________ and ultrasound ___________________. Most people hear sounds between 20 hertz and 20,000 hertz. • Infrasound is sound at frequencies ___________ than most people can hear. • Ultrasound is sound at frequencies __________ than most people hear. sonar imaging lower higher

16. Ultrasound Sonar is a technique for determining the distance to an object ______________________. Ultrasound imaging is an important medical technique. Computer software uses reflected pulses of ultrasound to make a detailed map of structures and organs inside the body. under water

17. Ultrasound Ultrasound imaging is an important ________________ technique medical

18. The Doppler Effect change The Doppler effect isa _____________ in sound frequency caused by ____________ of the sound source, motion of the listener, or both. motion As a source of sound _________________, an observer hears a higher frequency. When the sound source moves away, the observer hears a ______________ frequency. approaches lower

19. The Doppler Effect lower Observer A hears a ___________-pitch sound than observer B because the wave fronts are ____________ apart for observer A. farther Doppler Effect Sound

20. Hearing and the Ear Outer Ear Middle Ear Inner Ear Your ear is a complex system that consists of three main regions—the _________ ear, the _______ ear, and the __________ ear. Hammer Anvil Cochlea Auditory Nerve outer middle Eardrum Stirrup Ear canal inner

21. Hearing and the Ear The outer ear _______________ and focuses sound into the middle ear, which receives and ________________ the vibrations. The inner ear uses ____________ endings to sense vibrations and send signals to the ______________. gathers amplifies nerve brain

22. Hearing and the Ear Middle Ear Middle Ear The middle ear contains three tiny ________—the hammer, the anvil, and the stirrup. The three bones act as a ____________ system to amplify the motion of the eardrum. bones Hammer Anvil Stirrup lever

23. How Sound Is Reproduced Sound is recorded by converting sound waves into _______________ ____________ that can be processed and stored. Sound is reproduced by ________________ electronic signals back into sound waves. electrical signals converting

24. Music • Most musical instruments vary pitch by changing the ____________________ of standing waves. • In a wind instrument, ____________ are closed using fingers or valves to change the length of the standing sound wave. • For some stringed instruments, musicians change the length of the strings by pressing __________ with their fingers. frequency holes down

25. Music Resonance is the response of a standing wave to ______________ wave of the __________ ________________. Musical instruments often use resonance to _______________ sound. • One wave can “push” another wave to a higher amplitude. • Resonance can produce a dramatic increase in amplitude. another same frequency amplify

26. Music Sound-absorbing tiles in this auditorium reduce unwanted reflections. The curved reflecting panels above the stage help gather and direct sound waves toward the audience.

27. Assessment Questions • The intensity of sound waves is measured in units of • hertz (Hz). • decibels (dB). • joules (J). • meters (m).

28. Assessment Questions • Most musical instruments vary pitch by • changing the amplitude of sound waves. • reflecting sound from surfaces in a room. • changing the frequency of a standing wave. • using the Doppler effect.

29. Assessment Questions • The Doppler effect is • a change in sound frequency caused by motion of the sound source relative to the listener. • used in a variety of applications including sonar and ultrasound imaging. • a technique for determining the distance to an object under water. • the rate at which a wave’s energy flows through a given area.

30. Assessment Questions • What part of the human ear acts as an amplifier to increase the motion of the eardrum? • ear canal • middle ear • inner ear • auditory nerve