5.5 - Sound Waves & Hearing

• What are sound waves primarily composed of?

  Vibrations passing through molecules
• How do sound waves travel through materials?

  By causing particles to vibrate
• What type of wave are sound waves classified as?

  Longitudinal waves
• What are compressions in sound waves?

  Regions where particles are closest together
• What are rarefactions in sound waves?

  Regions where particles are furthest apart
• How do sound waves transmit through solids?

  By causing particles to collide and vibrate
• Why do sound waves travel faster in solids?

  Particles are more densely packed
• In which medium do sound waves travel slowest?

  Gases
• Why can't sound travel through a vacuum?

  There are no particles to vibrate
• What happens to the frequency of sound waves when they pass between different mediums?

  Frequency remains unchanged
• What does the equation speed = frequency × wavelength imply when speed increases?

  Wavelength must increase if frequency is constant
• How does wavelength change in higher density mediums?

  Wavelength gets longer as sound speeds up
• What happens to wavelength in low density materials like air?

  Wavelength gets shorter as sound slows down
• What phenomenon occurs when sound changes speed between mediums?

  Sound can be refracted
• What happens to sound waves when they hit hard flat surfaces?

  They are mostly reflected, causing echoes
• What are the main parts of the human ear involved in hearing?

  • Ear canal
  • Eardrum
  • Ossicles (three small bones)
  • Semicircular canals
  • Cochlea
  • Auditory nerve
• What happens when sound waves reach the eardrum?

  They cause the eardrum to vibrate
• How are vibrations transmitted from the eardrum?

  Through the ossicles to the cochlea
• What does the cochlea do with vibrations?

  Converts them into electrical signals
• How does the brain interpret electrical signals from the cochlea?

  As sounds with varying pitches and loudness
• What is the typical human hearing range?

  20 hertz to 20,000 hertz
• How does aging affect human hearing?

  Hearing range typically decreases with age
• What causes the decrease in hearing range as we age?

  Wear and tear of cochlea and auditory nerve
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• Sound waves are:

  Longitudinal waves
• In a longitudinal wave, the regions where the vibrating particles are closest together are called:

  Compressions
• In a longitudinal wave, the regions where the vibrating particles are the furthest apart are called:

  Rarefactions
• True or false? In a solid, sound waves travel by particles vibrating and colliding with their neighbours.

  True
• What happens when sound waves travel from a less dense medium, to a more dense medium?

  Their speed increases
• Sound travels at different speeds in different materials. Rank the speed of sound in the three states of matter in order of fastest to slowest:

  • Fastest: Solids
  • Middle: Liquids
  • Slowest: Gases
• Sound waves can be:

  Absorbed

  Reflected

  Refracted
• The frequency of a sound wave determines the pitch of the noise we hear. We hear higher frequency sounds as having a ________ pitch.

  higher
• The role of the ear drum is to:

  Transmit the vibrations of the sound wave to the ossicles 
• Cochlea: D

  Ossicles: C

  Ear drum: A

  Semicircular canals: B

  
• Can sound waves travel through a vacuum?

  • No
  • Sound waves rely on vibrating particles to travel. In a vacuum there are no particles that can vibrate and so sound waves can't be transmitted. 
• The role of the auditory nerve is to:

  Transmit the electrical signals from the cochlea to the brain
• The range of human hearing is approximately 20 Hz to 20,000 Hz
• As people get older, their hearing range can:

  • Decrease 
  • As people age damage from large sounds and general wear and tear reduce their hearing range.
• The role of the cochlea is to:

  Convert the vibrations into electrical signals