112: Properties of Sound

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11-2 Properties of Sound

• Workbooks openeveryone answers!

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Intensity and loudness

• The amount of energy a wave carries is called
  ______.
• Amplitude.
• Sound waves are _______ waves.
• Compressional
• On the next slide, you will be asked to
  categorize compressional waves.

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(No Transcript)
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Intensity

• Intensity is the amount of ______ that flows
  through an _____ in a certain amount of _____.
• Energy
• Area
• Time
• Sounds that are more intense can be heard _______
  away
• farther

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Intensity, cont.
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Intensity questions

• Which of the examples was low intensity?
• The girls whispering
• So then, the obnoxious guy with the megaphone
  exemplified high intensity. What did that mean
  for the people?
• The old man could hear the megaphone guy because
  high intensity waves travel farther.
• Why do high intensity waves travel farther?
• Each air molecule travels farther, giving it a
  better chance of colliding with other air
  molecules and transmitting the sound.

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Loudness

• Loudness is the _____ _____ of intensity.
• Human perception
• As intensity increases loudness ______.
• Increases
• Can you think of an example where something that
  seems to have a low intensity is actual very
  loud?
• Can you think of an example where something that
  seems very intense is actually not very loud?

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High Intensity at the speaker, but low
loudness because the distance is great.
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Seems like low Intensity, but the speakers are
so close the intensity is actually high (as is
the loudness).
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The Decibel Scale

• This scale measures sound ______.
• Intensity
• What is the faintest sound that most can hear?
• 0 dB
• What is the level of permanent hearing loss?
• 120 dB
• Why should this matter to you?
• We listen to headphones now a LOT of the time.
  They are close to our ears, so the intensity is
  high. Many of us will suffer permanent hearing
  damage.
• http//www.cdc.gov/niosh/topics/noise/abouthlp/noi
  semeter_flash/soundMeter_flash.html

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Pitch

• Pitch is
• How high or low the sound is.
• The higher the ______, the higher the pitch.
• Frequency

http//freesound.iua.upf.edu/samplesViewSingle.php
?id28636
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Above and below human hearing

• Sound waves with frequencies below what humans
  can hear are called
• Infrasonic waves
• Sound waves with frequencies above what humans
  can normally hear are called
• Ultrasonic waves
• What are some uses of ultrasonic waves?
• Medical diagnoses, finding underwater objects
• What sorts of things create infrasonic waves?
• Machinery
• Elephants (really!)

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Doppler Effect
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Doppler Effect, continued

• What does the engine sound like if the race car
  is moving toward you?
• Higher pitched
• Why?
• The waves bunch up together in front of the
  moving car
• What does the engine sound like if the race car
  is moving away from you?
• Lower pitched
• Why?
• The waves are separated behind the moving car

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Uses of the Doppler Effect
http//images.businessweek.com/ss/06/06/hurricanes
/image/doppler_radar.jpg
www.ieee-virtual-museum.org/.../jeUpUE3JAC41.jpg
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Uses of the Doppler Effect
stokes.byu.edu/redshift.jpg