Speed of Sound


1
The speed of sound is
346 m/s at room
temperature.
The speed of sound
depends on elasticity,
density, and
temperature of the
medium.
Properties of Sound



2
Intensity of a sound
wave is the amount of
energy that a wave
carries per second
through a unit area.
Loudness describes
what you actually hear.
A sound wave of
greater intensity
generally sound louder.
Sound Loudness



3
The loudness of sound
is measured in
decibels.
Threshold of hearing is
at 0 decibels.
Sound louder than 120
decibels can cause
pain and permanent
damage.
Frequency & Pitch



4
Frequency is the number of
sound waves that pass a
given point in a given
amount of time.
Human hearing is between
20 Hz and 20,000 Hz.
Ultrasound is sound waves
above the normal human
hearing range.
Frequency & Pitch



5
Infrasound are sound waves
that are below the normal
range of human hearing.
Pitch of a sound is a
description of how high or
low the sound seems to a
person.
Pitch of a sound that you
hear depends on the
frequency of the sound
wave.
:10
As the frequency of a sound wave
increases . . . .
Pitch increases.
Pitch decreases.
Pitch stays the
same.
HELP! I don’t get
it!
A.
B.
C.
D.
6
1
2
3
4
5
21
22
23
24
25
6
7
8
9
0
0
A.
10
11
12
13
14
0
B.
15
16
0
C.
17
D.
18
19
20
Resonance


7
Resonance occurs when the
frequency of the sound
waves and the natural
frequency of the objects are
the same.
If resonance occurs in an
object that is not flexible, the
object will break (shattering
of a glass).
The Doppler Effect



8
The apparent change in
frequency as a wave source
moves in relation to the
listener is called the Doppler
Effect.
As sound source moves
toward the listener, the
waves reach the listener
with a higher frequency.
The pitch appears to
increase because of the
Doppler effect.
According to the Doppler Effect, as a
sound is approaching you, . . . .
:10
Wavelength increases and
frequency decreases.
Wavelength decreases and
frequency increases.
Wavelength increases and
frequency increases.
Wavelength decreases and
frequency decreases.
1.
2.
3.
4.
0% 0% 0% 0%
W
1
2
3
4
5
9 21
22
23
24
25
6
7
8
9
10
11
12
13
14
e
av
l
h
gt
en
ea
cr
n
i
W
15
e
av
.
s.
l
h
gt
en
de
ea
cr
W
16
.
s.
e
av
l
h
gt
en
ea
cr
n
i
W
17
e
av
.
s.
l
h
gt
en
18
de
ea
cr
.
s.
19
20
Combining Sound Waves


10
Timbre describes the quality of the sound
you hear.
The blending of the fundamental tone and
the overtones makes up the characteristic
sound quality, or timbre, of a particular
sound.
Music


Music is a set of tones combined in ways that
are pleasing to the ear.
Types of instruments:
–
–
–
–
11
Strings
Brass
Woodwinds
Percussion
Noise

12
Noise has no pleasing timbre and no
identifiable pitch.
Interference of Sound Waves



13
Interference occurs when two or more sound
waves interact.
Acoustics describe how well sound can be
heard in a particular room or hall.
Repeated change in loudness are called
beats.
:10
What do we call sound that is pleasing
to the ear?
music
noise
timbre
acoustic
1.
2.
3.
4.
0%
m
1
2
3
4
5
1421
22
23
24
25
6
7
8
9
10
11
12
13
i
us
14
0%
c
no
15
e
is
0%
e
br
tim
16
17
0%
a
u
co
18
ic
st
19
20
Hearing Sound

15
The outer ear funnels
sound waves, the
middle ear transmits
the waves inward, and
the inner ear converts
the sound waves into a
form that your brain can
understand.
Outer Ear


16
The outer ear funnels
the sound waves to the
ear canal.
The sound travels down
the ear canal and
vibrates the eardrum.
Middle Ear


17
The middle ear
contains three small
bones: hammer, anvil
and stirrup.
The vibrations travel
from the eardrum to the
hammer, then the anvil
and finally the stirrup.
Inner Ear



18
The stirrup vibrates the
cochlea.
The cochlea contains
fluid and tiny hairs that
are stimulated by the
vibrations.
The stimulations of the
tiny hairs send
messages to the brain.
:10
Which of the following bones are found
in the ear?
anvil
hammer
stirrup
All three
er
m
m
2
3
4
5
1921
22
23
24
25
6
7
8
9
10
11
12
13
14
15
0%
A
ha
an
1
0%
e
0%
vi
l
0%
hr
e
4.
ll
t
3.
irr
up
2.
st
1.
16
17
18
19
20
Hearing Loss

Hearing loss is caused
by:
–
–
–
20
Injury
Infection
Aging (like me?)
Facts:





21
More than 40 million Americans have hearing loss.
Approximately 40% of the hearing-impaired are
under age 65.
About 2 million children under age 18 are hearingimpaired in the U.S.
Minor decreases in hearing, especially of higher
frequencies, are normal after age 20.
Some form of hearing loss affects 1 out of 5 people
by age 55.
Facts:




22
One-third of Americans between the ages of 65 and
74 - and one-half of those age 85 and older - have
some form of hearing loss.
Hearing loss is the third leading chronic disability,
following arthritis and high blood pressure.
Between 7 and 10 million people in American
industry have noise-induced hearing loss, virtually all
of which was preventable.
About 15% of college graduates have a level of
hearing loss equal to or greater than their parents; a
significant cause is listening to loud music.
Facts:


23
In the U.S., 12 million people have hearing aids.
Of the 12 million with hearing aids, only 6 million
actually wear them eight hours a day, seven days a
week.
Application of Sound



24
An echo is a reflected
sound wave.
Some surfaces absorb
sound waves.
Other surfaces reflect
sound waves
Sonar



25
Sonar is a system of
detecting reflected
sound waves.
Sonar stands for sound
navigation and ranging.
A sonar device
measures the time it
takes to detect the
reflected sound waves.
Ultrasound



26
Ultrasonic frequency is
sound waves above
20,000 Hz.
Echolocation is the use
of sound waves to
determine distance or
to locate objects.
Bats use echolocation
to navigate and to find
food.
Ultrasound (continue)



27
Ultrasound produce pictures called
sonogram.
Doctors use ultrasound to look inside the
human body and to diagnose and treat
medical conditions.
Ultrasound is used for focusing cameras,
brushing teeth and cleaning jewelry.
Test


28
This Friday, December 18th.
Covers all of sound waves in chapters 15 &
16.
Review Questions








29
What type of wave is sound?
(longitudinal)
What are three factors that affect the speed of
sound?
(elasticity, density & temperature)
What are the three bones in the middle ear?
(hammer, anvil & stirrup)
Is sound faster in warmer or cooler temperatures?
(warmer)
Review Questions








30
Is sound faster in elastic material or material that is
not elastic?
(elastic)
Is sound faster in less dense or more dense
medium?
(less dense)
What does the stirrup shake in the middle ear?
(cochlea)
What does sonar stand for?
(sound navigating and ranging)
Review Questions







31

How do bats navigate?
(echolocation)
What effect describes an increasing pitch as a loud
noise is approaching and decreasing pitch as a loud
noise is moving away?
(Doppler Effect)
What is the property of sound that is described as
the amount of energy that passes by a point each
second?
(intensity)
How loud or soft noise is appears to be is known as
___________.
(pitch)
Review Questions








32
What you hear is known as _______________.
(loudness)
Sound is measured in ________________.
(decibels)
Sound waves with frequencies below the human
range of hearing is known as _______________.
(infrasound)
Sound waves with frequencies above the human
range of hearing is known as _______________.
(ultrasound)
Review Questions








33
When the frequency of an object and the natural frequency are
the same, it is known as _______________.
(resonance)
_______________ describes the quality of sound.
(timbre)
What group of instrument vibrates the lips to produce sound?
(brass)
What group of instruments vibrates a reed to produce sound?
(wood-wind)
Review Questions








34
What group of instruments produces sound by rubbing,
plucking or striking a string?
(string)
What group of instruments produces sound by being struck?
(percussions)
Sound with no identifiable pitch and unpleasing to the ear is
known as _______________.
(noise)
Sound pleasing to the ear with an identifiable pitch is known as
_______________.
(music)
Review Questions


35
_______________ describes how well sound can be
heard in a particular room.
(acoustics).