Sound

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Sound

• The Nature of Sound
• Chapter 21

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Objectives

• Physical Standard 1
• I will be able to describe sound wave
  characteristics that are common among other forms
  of waves.
• I will be to differentiate unique characteristics
  of sound.
• THINK Why is sound important?

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Close Your Eyes and Listen
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• Sound waves
• Interactions
• of sound
• Reflection

• travels through a medium (solid, liquids or
  gases)
• longitudinal wave
• Sound travels by sending vibrations -back and
  forth motion - through matter
• Pair and Share Why cant you hear sound in
  outer space? How do they communicate with each
  other?
• reflected sound called an echo
• hard, smooth surface stronger reflection

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Reflection
Sound Waves
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REVIEW WAVE

• Bending of sound waves as it passes from one
  medium to another
• Bending of waves around a barrier
• sound waves meet
• constructive? increases sound
• destructive? decreases sound
• at room temp, sound travels at 343 m/s
• speed depends on medium it travels though

• Refraction
• Diffraction
• Interference
• Illustrate the three above
• Speed of Sound

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Mediums and Sound

• more elastic a medium? faster sound travels
• Solid fastest speed
• Liquid medium speed
• Gas slow speed
• Vacuum no sound
• sound travels slower in dense materials
• sound travels slower at lower temperatures and
  higher altitudes
• Pair and Share Why does this happen?

• Elasticity
• Density
• Temperature

8
Properties of Sound

• describes your perception of the energy of a
  sound
• describes what you hear
• depends on 2 factors
• energy of sound source
• distance from sound source
• The Coolest Things Sound Wave Can Do
• Find someone and share video

• Loudness

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• Energy of a sound source
• Think Draw an example
• Distance from a sound source
• Think Draw an example

• greater energy used ? louder sound
• more energy ? greater amplitude (vibration)
• large amplitude ?loud sound
• loudness increases the closer you are to a sound
  source

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• amount of energy a sound wave carries per second
  through a unit area
• greater intensity sounds louder
• unit decibel (dB)
• sound barely heard 0 dB
• sound louder than 100 dB can damage ears

• Intensity
• Measuring
• Loudness

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• Pitch
• Pitch
• Frequency
• Pitch and Frequency Video

• description of how high or low the sound seems to
  a person
• depends on frequency of the wave
• high frequency ? higher pitch
• low frequency ? low pitch
• can hear sounds with frequency between 20 Hz and
  20,000 Hz

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• Ultrasound
• Infrasound
• Doppler Effect

• sound waves with frequency above normal human
  range
• frequency below human range of hearing
• change in frequency of a wave as its source moves
  in relation to an observer
• change in frequency is heard as a change in pitch

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• Shock Waves
• Sound Quality

• shock waves form as sound waves overlap
• release huge amounts of energy
• sonic boom heard when they pass by
• Blending of several pitches through interference

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• Noise
• Music

• Random mix of frequencies that are
• not pleasing
• set of frequencies that combine in patterns that
  are pleasing

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How you Hear Sound

• function gather sound waves and send info to
  brain
• three main sections outer, middle, inner
• collects sound waves and directs them to ear
  canal which vibrates eardrum

• Human Ear
• Outer Ear

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• Middle Ear
• Inner Ear

• contains 3 small bones that increase size of
  vibrations
• Vibrations are changed into electrical signals
  for the brain to interpret

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• can occur if eardrum is damaged
• loud sounds can damage hair cells in inner ear?
  wont get messages to brain
• old age? hair cells gradually die? harder to hear
  
• amplify sound

• Hearing Loss
• Hearing Aids

21

• -use of reflected sound waves to determine
  distances or locate objects
• -animals use this to navigate and find food ?
  Bats, dolphins

• Echolocation

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