Name
Sound
Date
■
Class
Adapted Reading and Study
Properties of Sound
Loudness
(pages 42–47)
(pages 42–44)
Key Concept: The loudness of a sound depends on
two factors: the amount of energy it takes to make the
sound and the distance from the source of the sound.
• Loudness is how loud or soft a sound seems to the
person who hears it.
• The more energy it takes to make a sound, the louder
the sound. For example, pounding hard on a door with
your fist makes a louder sound than tapping gently on a
door with your fingers.
• The closer you are to the source of a sound, the louder
the sound. The whisper of a person next to you is louder
than the whisper of a person across the room.
• The loudness of a sound is measured in decibels (dB).
The loudness of a whisper is about 20 dB. The loudness
of a rock concert is about 120 dB.
Answer the following questions. Use your textbook and the
ideas above.
1. Circle the letter of each sentence that is true about
loudness.
a. Louder sounds take more energy to make.
b. Moving away from the sound source makes a
sound louder.
c. Loudness is measured in decibels.
2. Is the following sentence true or false? Sounds are
louder when you are closer to them.
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22
Name
Sound
Date
■
Class
Adapted Reading and Study
Pitch
(pages 44–45)
Key Concept: The pitch of a sound that you hear
depends on the frequency of the sound wave.
• Pitch is how high or low a sound seems to a person
who hears it. The sound of a whistle has a high pitch.
The sound of thunder has a low pitch.
• The pitch of a sound depends on the frequency of the
sound waves. A sound wave with a higher frequency
makes a sound with a higher pitch.
• Humans can hear only a certain range of pitches. A
sound that is too high for humans to hear is called
ultrasound. A sound that is too low for humans to hear
is called infrasound.
• Music uses certain pitches called notes. When you sing
or play a musical instrument, you keep changing pitch.
Answer the following questions. Use your textbook and the
ideas above.
3. How high or low a sound seems to a person who hears
it is the
.
4. Is the following sentence true or false? The pitch of a
sound depends on the frequency of the sound waves.
5. Fill in the blanks in the table about types of sound.
Types of Sound
a.
too high for humans to
hear
b.
too low for humans to
hear
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23
Name
Sound
Date
■
Class
Adapted Reading and Study
The Doppler Effect
(pages 46–47)
Key Concept: When a sound source moves, the
frequency of the waves changes because the motion
of the source adds to the motion of the waves.
• The Doppler effect is a change in pitch that happens
when a sound source is moving. For example, when a
fire truck races by you, the sound of the siren changes
pitch.
• When a fire truck is coming toward you, the truck is
moving in the same direction as the sound waves you
are hearing. This makes the waves closer together. The
waves have a higher frequency, so the sound has a
higher pitch.
• When the fire truck is going away from you, the truck is
moving in the opposite direction from the sound waves
you are hearing. This makes the waves farther apart.
The waves have a lower frequency, so the sound has a
lower pitch.
Answer the following questions. Use your textbook and the
ideas above.
6. Which property of a sound wave changes in the
Doppler effect? Circle the letter of the correct answer.
a. loudness
b. speed
c. frequency
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24
Name
Sound
Date
■
Class
Adapted Reading and Study
7. Both people in the picture hear the fire truck’s siren.
Which person is hearing a lower pitch? Which person is
hearing a higher pitch?
a.
b.
FIRE DEPARTMENT
DE
E
a.
b.
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25