Sound Waves

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Sound Waves
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What is sound?

• Its a disturbance that travels through a medium.
• Sound travels in a wave with
  the molecules of the medium close in a
  and farther away in a
  .
• Sound waves can travel in
  and , but not in outer space because
  there are

longitudinal
compression
rarefaction
liquid,
gas,
solid
no molecules for
compression or rarefaction to transmit waves.
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Speed of Sound

• At room temperature, the speed of sound is
• The speed of sound waves depends on
• Temperature low slow, high fast
• Density low (thin) fast, high (thick) slow
• Elasticity high fast, low slow

342 m/s.
How well a material bounces back after a
distrubance.
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Describing Sound

• Sound can be described by its
• Intensity how much energy is carried in a wave
  in 1 second over a specific area
• Loudness whats actually heard measured in
  decibels (dB)
• Frequency how much vibration there is because
  of a wave
• Pitch how high or low a sound is to an
  individual person it depends on the frequency of
  the sound

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Whats heard

• The human ear naturally hears frequencies between
  and
• Those sounds below the threshold are called
• Those sounds above the threshold are called
• If a sound has the same frequency as an object,
  they have resonance.

20,000 Hz.
20 Hz
infrasounds.
ultrasounds.
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What is the Doppler effect?

• When a sound seems to change its frequency when
  it really doesnt change.
• Waves are not evenly spread out in the front and
  back, so the person in the front hears more
  because the waves are more packed together than
  behind

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Technological uses of sound waves

• SONAR
• Sound Navigation and Ranging
• Sound waves are reflected back
• Ships and subs use
• Ultrasound and Infrasound
• Use echolocation to locate objects
• Bats, whales, and dolphins use to communicate and
  find food
• Doctors use to look at organs and babies
• Cameras use it to focus on objects

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Listening

• Observations of music
• Observations of singing bowl