Sound Waves

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Sound Waves

• How We Hear
• Properties of Sound
• Using Sound

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Objectives

• I will continue to learn about the properties of
  sound.
• Homework
• Packet page 7.

3

• As the frequency of a sound wave increases
• Pitch increases.
• Pitch decreases.
• Pitch stays the same.
• HELP! I dont get it!

4
Differences in Waves

• This ear-shaped boat moves up and down as the
  waves arriveas your eardrum does!
• Which waves are soft? Loud?
• Which waves are low? High?

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A
B
highest amplitude
highest amplitude
loudest
loudest
lowest frequency
highest frequency
lowest pitch
highest pitch
D
C
lowest amplitude
loudest
highest amplitude
softest (quietest)

• Which sound wave(s) has the
• lowest amplitude?
• highest amplitude?
• lowest frequency?
• highest frequency?
• lowest pitch?
• highest pitch?
• softest (quietest)?
• loudest?

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Speed of Sound

• The speed of sound depends on the properties of
  the medium through which it is traveling

7

• Elasticity is the ability of a material to bounce
  back after being disturbed.
• More elastic faster
• Solid most elastic
• Liquid not very elastic
• Gas inelastic
• Density is the amount of matter in a given
  volume.
• More density particles closer faster
• Temperature is a measure of the average kinetic
  energy.
• Higher temperature faster
• Lower temperature slower

8
Graph the following data
Show how the speed of sound through air changes
with temperature. Show temperature from -20C
to 30C on the horizontal axis. Plot speed from
300 m/s to 400 m/s on the vertical axis.
Should you choose a line graph or a bar graph for
this data?
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Breaking the Sound Barrier

• When an object passes through the air, it creates
  a series of pressure waves in front of it and
  behind it.
• These waves travel at the speed of sound,
• As the speed of the object increases, the waves
  are forced together, or compressed, because they
  cannot "get out of the way" of each other.
• When the object reaches the speed of sound, the
  waves merge into a single shock wave.
• This critical speed is known as Mach 1761 mph!!

Rapid condensation of water vapor due to a sonic
shock produced at sub-sonic speed creates a vapor
cone
10
Moving Faster than Sound

• Oct. 14, 1947, Chuck Yeager became the first
  person to fly faster than the speed of sound. He
  flew at a high altitude in order to do this.
  Why?
• At higher altitudes the air is colder, so sound
  travels more slowly.
• So, to break the sound barrier at a high
  altitude, he did not have to fly as fast as he
  would have at a lower altitude.
• LOWER TEMPERATURE
• SLOWER TRANSFER OF ENERGY
• LOWER SPEED OF SOUND

• Oct. 15, 1997, Andy Green became the first person
  to drive a land vehicle faster than the speed of
  sound. Why did he choose to drive in the desert?
• Cooler at night and in the morning
• Flat
• Large open spaces

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• The cracking sound a bullwhip makes when properly
  wielded is, in fact, a small sonic boom. The end
  of the whip, known as the "popper", moves faster
  than the speed of sound, thus resulting in the
  sonic boom.4 The whip is quite possibly the
  first human invention to break the sound barrier.

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Reflection of Sound Waves

• Echo- A reflected sound wave
• Smooth hard surfaces reflect best
• Rough soft surfaces reflect poorly
• Energy not reflected is absorbed or transmitted
  through the material

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Echolocation

• Echo- a reflected sound wave
• Echolocation- using the reflection of sound waves
  (echo) to navigate, locate prey, and to determine
  the direction and distance of objects
• Used by bats, dolphins, whales
• Can humans use echolocation?
• Use ears to interpret echoes (to estimate
  size/shape of room)
• Ben Underwood!

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• http//player.discoveryeducation.com/index.cfm?gui
  dAssetId5325917E-9D80-4965-91DE-00130A33A7FCblnF
  romSearch1productcodeUS

15
Extra Credit

• Draw a house and write down the measurements you
  used in centimeters AND millimeters.

• It MUST have a door and two windows.
• It MUST have a triangle roof.
• It must be colored and have grass and trees!

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Things we dont have senses for

• Ultraviolet Light (UV)
• some birds, butterflies, bees, fish
• Infrared (IR- heat)
• pit vipers
• Extra colors
• some birds, butterflies (4 receptors), mantis
  shrimp (12 receptors)
• Polarized light
• many insects

• Echolocation
• bats
• 3-D hearing
• owls
• Ultrasound
• whales, dolphins, bats
• Infrasound
• Elephants
• Water air currents
• fish, arthropods

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Bellwork

• What do bats, dolphins and elephants all have in
  common?
• They all use sound waves to help them to see,
  navigate, hunt, and communicate
• Can people ever do what makes these animals so
  unique?
• Yes! One such persons name is Ben Underwood and
  he has been using echolocation to help him see
  since he was a toddler

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Bat Echolocation
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Ultrasound

• High frequency sound waves ( 20,000 Hz)
• Echolocation is the use of sound waves to
  determine distance or to locate objects.
• Animals
• Use echolocation to navigate and to find food.
• Bats
• Ultrasonic echolocation to detect prey
• Moths
• Ultrasound emitted by bats causes flying moths to
  make evasive maneuvers, because bats eat moths.
• Dogs
• Dog whistle? 16 kHz - 22 kHz
• Dolphins
• Hear ultrasound, have their own natural sonar
  system
• Medicine
• Alternative to surgery focusing sound waves on
  kidney stones or gallbladder stones can break
  them up so that they may be safely passed through
  the body
• Make images on the inside of the body
• Examine developing fetus
• Examine internal organs

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Infrasound

• Low frequency sound waves (less than 20 Hz)
• Communicate over varying distances of up to many
  miles
• Waves are diffracted around objects because of
  the long wavelength
• Animals
• Elephants
• allow them to communicate over long distances
• Whales
• Hippopotamuses, rhinoceros, giraffes
• Natural Earth Processes
• Ocean waves
• Avalanches, earthquakes, volcanoes
• Meteors
• Man-made Processes
• Explosions (chemical, nuclear)

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Discussion Questionshttp//player.discoveryeducat
ion.com/index.cfm?guidAssetId97994B64-8BBB-41D9-A
7D6-2CA443B39B5FblnFromSearch1productcodeUS

• What made scientists like Dr. Joyce Poole believe
  that elephants were communicating on a level that
  humans could not hear?

• Why does infrasound travel farther than the sound
  waves that humans can hear?
• What is truly unique about the way that bats
  hear?

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S o n a r

• Sonar- Sound Navigation And Ranging a system of
  detecting reflected sound waves
• Navigation- finding your way around
• Ranging- finding the distance between objects
• Used by submarines and ships
• Ship sends out a sound wave
• Sound wave hits the bottom
• Sound wave bounces back
• SONAR measures the time it takes to detect the
  reflected sound waves (long time far away)
• Map undersea features, detect submarines, schools
  of fish and other objects

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The Doppler Effect

• Change in wave frequency caused by a moving sound
  wave source
• moving toward you ? high pitch
• Waves pile up shorter wavelength higher pitch
• moving away from you ? low pitch
• Waves spread out longer wavelength lower
  pitch

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Music vs. Noise

• Music
• specific pitches and sound quality
• regular pattern
• tones combined in ways that are pleasing to the
  ear
• Noise
• no definite pitch
• no set pattern

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Instrument Presentation

• Maracas
• High-Pitch vs. Low-Pitch Instrument Presentation

• http//www.ehow.com/videos-on_2572_play-maracas.ht
  ml

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The key farthest to the left on a piano is
attached to the longest string. This key plays
the note with the lowest pitch.
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Musical Instruments

• Types of instruments
• Strings
• Brass
• Woodwinds
• Percussion
• Three ways to make sound
• Vibrate a string
• Vibrate an air column
• Vibrate a membrane

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Brass Instruments

• Sound is caused from a vibrating air column
  within the instruments body
• Vibrating lips allow sound waves to pass through
  the mouthpiece into the instrument
• Ex trumpet, French horn, tuba, cornet, baritone
• Changing Pitch (Frequency) in Brass
• Blow harder to make the air resonate at higher
  natural frequencies
• Pressing valves that change the length of the
  tube
• Changing Volume (Amplitude)
• Blowing into mouthpiece with more/less force

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Woodwind Instruments

• Sound caused by a vibrating reed and vibrating
  air column
• Mouthpieces contain 1 or 2 reeds that vibrate the
  air column when the musician blows into the
  mouthpiece
• Ex oboe, clarinet, saxophone, flute, piccolo
  (both involve the player blowing across a narrow
  opening to make the air column vibrate)
• Changing Pitch (Frequency) in Woodwinds
• Musician changes the length of the resonating
  column of air
• Close and open finger holes along the length of
  instrument
• Changing Volume (Amplitude)
• Blowing harder/softer into the mouthpiece

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Percussion Instruments

• Instruments are struck to make a sound, vibrating
  membrane
• Drums and Other Percussion Instruments
• Tightening the drumhead increases the natural
  frequency of the drum resulting in higher pitch
  sounds
• Striking the top surface causes it to vibrate
  the vibrating drumhead is attached to a chamber
  that resonates and amplifies the sound
• Steel drums play different pitches depending on
  where you hit them at, and do not need a chamber
  to resonate and amplify the sounds
• Some have fixed pitch
• Xylophones have wooden or metal bars of different
  lengths
• The longer the bar, the lower the sound
• The shorter the bar, the higher the sound

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Strings Instruments

• Strings, like vocal cords, vibrate back and forth
  as air is forced past them, which creates a
  series of compressions and rarefactions in the
  air vibrating strings
• Amplifying Vibrations
• Sound produced by a vibrating string is soft, to
  amplify the sound, instruments have a hollow
  chamber, or a resonator
• Resonator contains air and absorbs energy from
  the vibrating string and vibrates at its natural
  frequencies

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(No Transcript)
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• FREQUENCY AND PITCH
• After reading this section you will be able to do
  the following
• Explain how you can change pitch by altering
  sources.
• Describe what resonance is.
• http//www.learnanytime.co.uk/Science/Sound20(1).
  htm
• DEMO
• http//www.ndt-ed.org/EducationResources/HighSchoo
  l/Sound/frequencypitch.htm
• http//www.bbc.co.uk/schools/scienceclips/ages/9_1
  0/changing_sounds_fs.shtml
• http//www.catie.org.uk/GS_pitch_page.html
• http//www.harcourtschool.com/activity/science_up_
  close/521/deploy/interface.html

34
Sound Review

• What type of wave is sound?
• longitudinal
• What are the three bones in the middle ear?
• hammer, anvil stirrup
• What are three factors that affect the speed of
  sound?
• elasticity, density temperature
• Is sound faster in warmer or cooler temperatures?
  
• warmer

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Sound Review

• 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

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Sound Review

• 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 high or low sound appears to be is known as
  ___________.
• pitch

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Sound Review

• The loudness of sound is measured in
• decibels
• What are sound waves with frequencies below the
  human range of hearing is known as?
• infrasound
• What are sound waves with frequencies above the
  human range of hearing is known as?
• ultrasound

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Sound Review

• When the frequency of an object and the natural
  frequency are the same, it is known as
  _______________.
• resonance
• What group of instrument vibrates the lips to
  produce sound?
• brass
• What group of instruments vibrates a reed to
  produce sound?
• woodwind

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Sound Review

• 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