Transcript 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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All sounds are created by vibrations.
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A vibration is the complete back-andforth motion of an object or material.
•
The next slide shows how a stereo
speaker produces sound.
Components of Sound: Figure 1
Components of Sound
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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.
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.
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.
Components of Sound
•
•
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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.
Components of Sound: Figure 2
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.
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.
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?
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?
Section 2: Objectives
•
Compare the speed of sound in different media.
•
Explain how frequency and pitch are related.
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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.
Properties of Sound
•
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. The cooler the medium is, the
slower the speed of sound.
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 Hearing The
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.
Properties of Sound: Figure 1
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.
Properties of Sound: Figure 2
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).
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.
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.
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?
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?
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?
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?
Section 3: Objectives
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Explain how echoes are made, and
describe their use in locating objects.
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List examples of constructive and
destructive interference of sound
waves.
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Explain what resonance is.