Sound is a wave

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Sound is a wave

• S8P4 a Identify the characteristics of
  electromagnetic and mechanical waves.
• S8P4 d Describe how the behavior of waves is
  affected by medium (such as air, water, solids)

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Vocabulary

• Sound
• Vibration
• Vacuum
• Echolocation
• Sonar

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Sound is a type of mechanical wave

• Sound is a wave that is produced by a vibrating
  object and travels through matter
• A vibration is a rapid, back-and-forth motion
• The medium vibrates back-and-forth in the same
  direction as the disturbance, so sound waves are
  longitudinal waves.

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Sound in our body

• Sound-making instrument in your body is the vocal
  cords
• Vocal cords relax when you breathe
• They draw close together when you are about to
  speak so they can vibrate

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How sound waves are detected

• Ear collects sound waves
• Outer Earcollects the sound waves, reflects to
  the ear canal, hits the eardrum at the end of the
  ear canal and causes it to vibrate
• Middle Earvibrations travel through three bones
  (hammer, anvil, and stirrup) to the inner ear
• Inner EarCochlea, which contains tiny hairs that
  bend due to the vibrations, triggers cells to
  send electrical signals to your brain. Only when
  your brain receives and processes these signals
  do you actually hear a sound.

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Animation of ear

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• Drum
• Skin vibrates pushing particles in the air so
  they become compressed and moving out
• When the drum pushes the opposite direction, the
  particles do not compress
• longitudinal wave

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Vacuum

• A vacuum is empty space,
• has no (or very few) particles
• Robert Boyle proved that
• sound does not travel
• through a vacuum
• Bell inside a sealed jar and
• pumped all the air out, as
• he pumped the air out, the
• sound got quieter until it finally
• quit

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Important Info on Sound

• Is a mechanical wave
• Only moves through a medium made of matter
• Cannot travel through a vacuumtherefore, it
  cannot move through space!

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The speed of sound

• Sound travels slower than light
• Two factors that affect the speed
• Material of medium
• Temperature
• Materials
• Sound travels faster through liquids than gases,
  because of the amount of particles
• Sound can travel through elastic solids very
  rapidly (steel)

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The speed of sound

• Temperature
• Sound travels faster at higher temperatures than
  at lower temperatures
• In hotter temperature the particles move faster
  making it easier to transfer sound waves
• Sound waves will travel slower when someone yells
  in a snow storm than when someone talks softly on
  a hot summer day

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Sound has many uses

• S8P4 e Relate the properties of sound to
  everyday experiences.

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Ultrasound Waves

• Humans and Animals use ultrasound waves to detect
  objects
• Bats use the echoes to find food
• People use it to detect objects underwater and/or
  to produce images of the inside of the body
• Sound waves are used for much more than just
  communication!!

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Echolocation

• Echolocation is the sending out of ultrasound
  waves and interpreting the returning sound echoes
• Animals use echolocation to find food
• Bats
• Dolphins
• Toothed Whales
• Porpoises

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Bats use sound to locate objects.
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Sonar

• People use the principle of echolocation to
  locate objects underwater which uses the echoes
  to produce an image on a screen
• A sonar is an instruments that uses echolocation
  to locate objects (sonar stands for sound
  navigation and ranging)
• Used to locate enemies (submarines)
• Find lost ships
• Find schools of fish
• Map the sea floor

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Medical Uses

• Can be used at high intensities because it cannot
  be heard by humans, therefore will not damage our
  hearing
• Used to
• Break up kidney stones
• Clean medical equipment
• Examine internal organs like the heart, pancreas,
  bladder, ovaries, and brain
• Examine blood flow

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Medical Uses

• Most common is the check on the health of a fetus
  during pregnancy
• Helps determine gender of the baby
• How many fetus there are
• If there are any medical, or genetic, issues
• The reflected ultrasound waves are used to create
  a picture called a sonogram

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Ultrasound pictures Sonograms
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Sound waves produce music

• Music is sound with clear pitches or rhythms
• Noise is random sound and has no intended pattern
• All of the pitches, together with the resonance
  of the instrument, produce its characteristic
  sound

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Musical Instruments

• There are three main types of instruments
• Stringed
• Wind
• Percussion
• Will discuss these later!!

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Sound can be recorded or reproduced

• Back in the daythere was no way to record or
  reproduce our voices.
• In the late 1800s, two inventions changed the
  world
• 1876-the telephone was invented
• 1877-phonograph was invented which was a sound
  recording machine

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The telephone

• Made long-distance communication possible
• Telephones do two things
• Translate the sound into a signal
• Reproduce the sound that arrives as a signal

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How the phone works
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Recorded sound

• This is a way to preserve sound because sound do
  not stick around, it is in real-time only
• A recorder has a needle that takes the vibrations
  and cuts into a piece of foil. The grooves
  contain the information needed to reproduce the
  sound.
• To play back, another needle is used to track
  along the foil
• Now recorders change the sound waves into
  electrical signals as magnetic information
  instead of making holes