Bellringer – 2 mins to hand in
 A 67kg ice skater is
moving at a constant
velocity of 10m/s when he
collides and holds onto a
50kg ice skater who was
originally at rest. What is
their momentum after
the collision?
DO
STOP
WORK
Objectives
 Learn more about the history of our understanding of
the universe.
 Spring cleaning
Late Labs
 Remember to turn in your late labs!
 You’re losing points every day they’re late!
Cosmos Episode Three
 Pre-video questions
1. What does “Cosmos” mean?
 The universe seen as a well-ordered whole
2. What did Robert Hooke discover?
3. What did Newton discover?
4. What did Halley discover?
5. What is a “light-year”?
New Bellringers
 If you’re absent or late you need to see me ASAP to
make up the bellringer.
 I will enter the grades once a week.
Cosmos Episode Three
1.
2.
3.
4.
5.
How has our natural ability for pattern recognition helped and
hindered societal advancements?
Why was it so difficult for Halley to publish Newton’s work?
Why was it so important for Newton’s work to be published
and how did it help to predict the future?
What were three scientific discoveries or inventions that
Halley made?
Describe what will happen when the Milky Way and
Andromeda galaxies finally meet up.
Bellringer – 2 mins to hand in
 A 53kg boy is held at rest
on a swing that is 1.5m
above its lowest point.
What is the boys
maximum velocity as he
swings through his
lowest point?
DO
STOP
WORK
Objectives
 Finish Cosmos Video
 Understand how sound waves travel.
Cosmos Episode Three
1.
2.
3.
4.
5.
How has our natural ability for pattern recognition helped and
hindered societal advancements?
Why was it so difficult for Halley to publish Newton’s work?
Why was it so important for Newton’s work to be published
and how did it help to predict the future?
What were three scientific discoveries or inventions that
Halley made?
Describe what will happen when the Milky Way and
Andromeda galaxies finally meet up.
Bellringer – 2 mins to hand in
 Explain how the total
mechanical energy of a
swinging pendulum is
conserved.
DO
STOP
WORK
Objectives
 Learn the basics of sound waves.
 Act like a bat and use sound waves to calculate dinner
time.
What does sound do for us?
Making Sound
 Put your fingers against your throat and then hum.
What do you feel?
 As your vocal cords move forward, air particles are
driven forward and create high pressure.
 As your vocal cords move backwards they create low
pressure.
Making Sound
Making Sounds
Small Slinky Demo
 Which direction does a high pressure want to move?
 Which direction does a low pressure want to move?
 Does the slinky move or vibrate?
Making Sound
 Collisions of the low and high air pressure areas cause
the variations to move from the tuning fork in all
directions.
 If you were to focus on one spot, you would see the
value of the air pressure rise and fall.
Describing Sound
 A pressure oscillation that is transmitted through
matter is a sound wave!
 Sound waves travel through air because a vibrating
source produces regular variations, or oscillations, in
air pressure.
Describing Sound
 Sound waves are longitudinal waves because the
motion of the particles in air is parallel to the direction
of the wave’s motion.
 The frequency of a sound wave is the number of
oscillations in pressure per second.
 The wavelength is the distance between successive
regions of high pressure or low pressure.
Describing Sound
 Just like any other wave the speed of sound depends on
the medium through which it is traveling.
 Air temperature changes the speed of sound,
increasing about .6m/s for every 1 degree Celsius
increase.
Sound Through Different Mediums
 Let’s Race: Solid vs. Gas!
 In general the speed of sound is greater in solids and
liquids than in gases.
Sound Without a Medium
 What happens if we remove the medium for sound to
travel through?
 Demo Time!
 Write down what you observe!
Properties of Sound Waves
 Sound waves share the general properties of other
waves!
 Sound waves can reflect off of hard surfaces, such as
the walls of a room, or the bottom of a well.
 Reflected sound waves are called “Echoes”.
Echoes
 If you know the speed at which a sound wave is
traveling you can calculate how far away you are from
something by timing how long it takes a sound wave to
leave you, bounce off of something, and then return
back to you.
 Bats, some cameras, and ships with sonar use this idea!
Echoes
 Bats call it
echolocation.
 Dolphins call it
echolocation.
 Submarines call it
sonar (SOund
Navigation And
Ranging).
Sonar
Sonar
 https://www.youtube.com/watch?v=-fAAxEIFeLU
 How has sonar helped scientists save fish populations?
 How has sonar helped scientists gather information
about the bottom of the ocean?
Sonar
Echolocation
 https://www.yo
utube.com/watc
h?v=bAvoz_ofoe
o
Echolocation and Sonar Practice
 Sound waves travel at about 1,484m/s in water, and about 343m/s
in air.
 If a bat counts 0.013 seconds between releasing a sound wave and
then hearing it return, how far away is its dinner?
𝑑
𝑡
𝑚
343
𝑠
 𝑣=

𝑑
=
0.013𝑠
 d=4.5m
 However the bat’s dinner is only 2.25 meters away because 4.5
meters is the distance the sound waves travels back and forth
between the bat and the dinner.
Echolocation and Sonar Practice
 Sound waves travel at about 1,484m/s in water, and
about 343m/s in air.
1. If a submarine spots a large blip on its sonar are
screen that is 0.25s away, how far away is danger?
 185.5 meters
2. If a dolphin hears Nemo o.oo1s away, how far away is
the end of Nemo?
 0.75 meters
Bellringer – 2 mins to hand in
 How far away is the whale
from the shore if it
measures a time of 0.52
seconds between
emitting and hearing the
sound wave return from
the shore?
DO
STOP
WORK
Bellringer
DO
STOP
WORK
Objectives
 Practice your sonar skills
 Learn and explain sound wave interference
 Learn the different ways of detecting sound
Echolocation and Sonar Practice
 What is the speed of sound in a mystery liquid if the
sonar gun records a time of 0.5 seconds between being
sent out, reflecting off a target 125 meters away and
then returning?
𝑣=
𝑣=
𝑑
𝑡
250𝑚
0.5𝑠
=
𝑚
500
𝑠
Sound Wave Interference
 Like other waves, sound waves can interfere with each
other when they meet.
 Will constructive interference make the sound louder
or weaker?
 Which will have a greater volume, a node or an
antinode?
Sound Wave Interference
Sound Interference Demo
 https://www.youtube.com/watch?v=qfJw1_vEKFo
 Warning: This may cause severe headaches.
Surround Sound
 Take a piece of paper and roll it into a tube.
 Is the sound really only on one side?
 Your brain calculates the time difference between both
of your ears hearing the same noise to figure out which
direction that noise came from.
Surround Sound Headphones
 https://www.youtube.com/watch?v=oPTa4
_HrPhs
 How do they calculate the time
differences?
 They just record with two microphones
about a head width apart. Your brain does
all the timing calculations!
Listening
Sound Detectors
 Sound detectors transform sound energy (KE of
vibrating particles of the medium) into electrical
energy.
 Microphones
 How do you think microphones convert kinetic energy
into electrical energy?
Microphones
 Waves and
electromagnetism!
 It’s like a speaker in
reverse.
The Human Sound Detector
 We don’t have coils and magnets in our ears, but we can
still convert the vibrating energy in the air into a different
form of energy.
 Simply, our eardrum is shook by the vibrating air, then the
eardrum shakes very tiny auditory bones which transfer
these vibrations into the fluid in the cochlea. There are
nerves in the fluid that pick up these vibrations and send
them to the brain to be interpreted.
The Ear
The Broken Ear
 Your eardrum is a
membrane that is meant
to keep stuff from
slipping into your
head…it can be broken 
 Like most of your body it
will heal if ruptured.
Checkpoint
1.
How do microphones pick up sound?
2. How do our ears pick up sound?
What Can We Hear?
 Our ears can’t hear every sound!
 On average people can hear between 20Hz and 20,000Hz
 https://www.youtube.com/watch?v=qNf9nzvnd1k
 So what happens as 5Hz or 50,000Hz?
 If tones are at a higher volume and “pure” we can hear more.
 https://www.youtube.com/watch?v=VxcbppCX6Rk
 How old are your ears?
Animals for the win!
 Many animals, such as dogs, cats, elephants, dolphins,
whales, and bats, are capable of hearing sounds at
frequencies that humans cannot hear.
 Low frequencies travel further than higher frequencies
because lower frequencies have less air friction.
Bellringer – Not Collected
 What is the frequency range of the average human?
Objectives
 Learn more sound vocabulary
 Use the your knowledge of the Doppler Effect to
predict pitch changes
Whales and Dolphins
 How the NAVY killed the whales
 https://www.youtube.com/watch?v=wM6AO31XHYs
 https://www.youtube.com/watch?v=kT5ALnnJzl0
 How dolphins help the NAVY
 https://www.youtube.com/watch?v=2FMwlHm2ts8
Bellringer
DO
STOP
WORK
Updates
 SLC today after school
Objectives
 Be able to explain what causes a sonic boom.
 Begin to understand how sound waves resonate in
instruments.
Perceiving Sound
 The pitch we hear depends on the frequency of
vibration
 The higher the frequency, the higher the pitch
 The loudness of a sound is the intensity of the sound,
which depends primarily on the amplitude of the
pressure wave.
Perceiving Sound
 Regular air pressure is 1 atmosphere, the ear can detect
pressure-wave amplitudes of less than one-billionth of
an atmosphere.
 Difference between 1.0 atm and 1.000000001 atm
Perceiving Sound
 Why do you think your ears start to hurt if you change
your elevation quickly?
 0.0002 atmospheres of pressure can cause pain, but
only if it is vibrating at an audible frequency.
 We would be in constant pain if the pain happened at
any frequency.
Perceiving Sound
 Humans can detect a wide range of intensities, so it is
convenient to measure these intensities on a
logarithmic scale called sound level.
 The most common unit of measurement for sound
level is the decibel (dB)
Decibels – Logarithmic Scale?
Decibels
 The sound level depends on the ratio of the intensity
of a given sound wave to that of the most faintly heard
sound.
 The faintest sound is measured at 0 dB
Decibels
Decibel Danger!
 Ear can lose sensitivity, especially to high frequency,
after exposure to loud sounds.
 Short term exposure is usually recovered from within a
few hours.
 Long term or chronic exposure can lead to permanent
damage.
Decibel Danger!
 To preserve your hearing
you shouldn’t listen to
loud music, shoot guns
without ear protection, or
use loud machinery like
jack hammers in your
spare time.
Checkpoint
1.
What determines the pitch of a sound?
2. What determines the volume of a sound?
3. Should you listen to your music at full volume?
Why?
The Doppler Effect
 The change in frequency of sound caused by the
movement of either the source, the detector, or both is
called the Doppler Effect
 NASCAR!
 https://www.youtube.com/watch?v=kyB-e1w-Mdo
The Doppler Effect
The Doppler Effect
 As the source moves towards the detector the waves
are crowded together, which shortens the wavelength.
 Because the speed of sound is not changed, more
crests reach the ear each second, which means the
frequency of the detected sound increases.
The Doppler Effect
 When the source is moving away from the detector the
wavelength is lengthened and the frequency is
decreased.
 A Doppler shift also occurs if the detector is moving
and the source is stationary.
The Doppler Effect
 As the detector approaches a stationary source, it
encounters more wave crests each second than if it
were motionless, and a higher frequency is detected.
 If the detector recedes from the source, fewer crests
reach it each second, resulting in a lower frequency.
Doppler Effect Slinky
 Demo
 Slinky
 NASA car
 Orange dude
Checkpoint 1
What happens to the frequency of an ambulance
siren as it drives towards you?
 It increases, higher pitch
2. What happens to the frequency of an ambulance
siren as it drives away from you?
 It decreases, lower pitch
1.
Checkpoint 2
What happens to the wavelength of an ambulance
siren as it drives towards you?
 It decreases, waves smooshed together
2. What happens to the wavelength of an ambulance
siren as it drives away from you?
 It increases, waves spread apart
1.
Doppler Demos
 Doppler Darts
 Doppler Disk
 Doppler Rodeo
Bellringer – 2 mins to hand in
 If a sound wave travels at
343m/s and has a
wavelength of 20m what
is its frequency?
 Can the average human
hear it?
DO
STOP
WORK
Bellringer
DO
STOP
WORK
Updates
 SLC today after school
Objectives
 Be able to explain what causes a sonic boom.
 Begin to understand how sound waves resonate in
instruments.
The Sound Barrier
 What happens if you’re moving at the speed of sound?
 Remember, sound can only travel at a certain speed.
 When traveling at the speed of sound the sound waves
become so smooshed together that they are all sitting
on top of each other and constructively interfere.
Sonic Boom
 Mach 1
 An object traveling
at the speed of
sound
 What happens
when we go faster?
Faster!
 As you go faster than the
speed of sound, the shape of
your pressure wake changes.
 There is still constructive
interference of sound waves,
they’re just in a different spot.
Sonic Booms
 The Sonic Boom does not only happen when you reach




the speed of sound.
It is continuously happening, like the wake coming off
of a boat.
You hear the sonic boom wave go past you.
Does the pilot hear the boom?
No the loud noise is behind them, and it moves slower
than the plane so it will never catch them!
Fighter Jets and Space Launches
 https://www.youtub
e.com/watch?v=ogtj
BcIjrjc
 When do you hear
the noise? Why?
 What’s up with the
cone cloud?
What else breaks the sound barrier?
 Most modern guns has a muzzle velocity that is faster
than the speed of sound.
 The end of a bullwhip can travel faster than the speed
of sound.
 https://www.youtube.com/watch?v=YNKPIOelTgA
 Satellites.
 Why don’t satellites make sonic booms as they pass over
us?
Checkpoint
1.
What causes a sonic boom?
 Constructive interference of the sound waves.
Sources of Sound
 Humans have figured out many different ways to
produce sound using vibrations
 Speaker cone, drums, cymbals
 Brass instruments (trumpets, tubas, trombones, etc.)
 Reed instruments (clarinet, saxophone, bassoon, etc.)
 Open wind instruments (flutes, organ pipes, etc.)
 String instruments (guitars, cellos, pianos, etc.)
Resonance in Air Columns
 Remember, resonance increases the amplitude of a
vibration by repeatedly applying a small external force
to the vibrating air particles at the natural frequency of
the air column.
 The length of the air column determines the natural
frequencies of the air column.
Resonance in Air Columns
 Changing the length of the column of vibrating air
varies the pitch of the instrument.
 The mouthpiece or reed simply creates a mixture of
different frequencies, and the resonating air column
acts on a particular set of frequencies to amplify a
single note, turning noise into music.
Trombone
 https://www.youtube.com/watch?v=CzX7FkxwXYo
 If the speed of sound is constant, why does the frequency
of the sound wave get lower has the slide length is
increased?
 Trombone dude…
 https://www.youtube.com/watch?v=soDn2puEuL8
Closed-Pipe Resonance
 A closed-pipe resonator is a pipe that has one closed
end and one open end.
 For a trombone the closed end is the mouthpiece, and
the open end is the bell of the horn.
Which waves will resonate?
 All waves will have a node
at the closed end of the
pipe.
 Only the waves that have
an antinode at the open
end of the pipe will
resonate.
Finding wavelength
 What is the wavelength
of the standing wave in
each pipe if the pipe is 1
meter long?
4m
 4/3 m
 4/5 m
Closed-Pipe Resonator
 A simple air column resonator can be made by placing
a pipe in a bucket of water, while holding a vibrating
tuning fork above it.
 You can adjust the length of the pipe by raising or
lowering it in the water.
 The end of the pipe is the closed end, the other end is
the open end.
Bellringer
DO
STOP
WORK
Objectives
 Complete lab
 Understand how beats work
Speed of Sound Lab
 You will experiment with
a variety of tuning forks
and pipe lengths to figure
out the speed of sound in
air!!!
Finding wavelength
 What is the wavelength
of the standing wave in
each pipe if the pipe is 1
meter long?
4m
 4/3 m
 4/5 m
Open-Pipe Resonance
 An open-pipe is open at both ends.
 The standing waves produced in an
open pipe must have antinode at
both ends.
 Only waves that have antinodes will
resonate in an open-pipe.
Air Column Practice
 What is the largest possible wavelength of a standing
wave that can produced in a 1.5m PVC pipe that is
closed at one end and open at the other?
 What is the frequency of this standing wave if the
speed of sound in air is 343m/s?
Air Column Practice
 What is the largest possible wavelength of a standing
wave that can produced in a 1.5m PVC pipe that is open
at both ends?
 What is the frequency of this standing wave if the
speed of sound in air is 343m/s?
Air Column Practice
 What are the wavelengths
of the standing waves in
the three pipes to the
right?
 2L
L
 3/2L
Bellringer
DO
STOP
WORK
Objectives
 Complete lab
 Understand how beats work
 Prepare for quiz
Updates
 Physics Club today!
 Team picture
 SLC on Thursday!
 First Review HW due on Friday!
Speed of Sound Two Lab
 10 minutes to complete
Sound Quiz
 This week or combine it with the next topic to make a
test?
Beats By Dre
 A beat is when two
frequencies that are
nearly identical
interfere to produce
oscillating high and
low sound levels.
Beats
 Demo
 Resonating Boxes
 Beat Demo
 https://www.youtube.com/watch?v=IQ1q8XvOW6g
 To calculate the frequency of the beat or the “Beat
Frequency” use the following equation
 𝑓𝑏𝑒𝑎𝑡 = 𝑓𝐴 − 𝑓𝐵
Beat Practice
 What will be the beat frequency between a 256Hz
tuning fork and a 250Hz tuning fork?
 6Hz
 If two tuning forks produce a beat of 4Hz and one of
the tuning forks is 384Hz what is the other tuning
fork’s frequency?
 Either 388Hz or 380Hz
Practice
 These are sample regents type questions about sound
waves.
 Odds
Sound Application Video
 https://www.youtube.com/watch?v=Ude8pPjawKI
 What are three things you can use sound waves to do?
Practice Written Response
 Page 433 numbers 72, 75, 77, 78, and 79.
 You’ve got 10 minutes.
Bellringer
DO
STOP
WORK
Objectives
 Prepare for quiz
Updates
 Quiz review today after school.
 SLC on Thursday!
 First Review HW due on Friday!
Practice
 These are sample regents type questions about sound
waves.
 Evens
Study Guide – 20%








Open Pipe Waves, Instruments
Standing Waves
Interference
Resonance
Beats
Echolocation
Doppler Effect
Sonic Boom