Sound waves and hearing

• What are sound waves essentially described as?

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

  As a series of compressions and rarefactions
• 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 travel through solids?

  By causing particles to vibrate and collide
• Why does sound travel faster in solids than in gases?

  Because particles are more densely packed
• Why can't sound travel through a vacuum?

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

  Their speed changes, but frequency remains constant
• 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
• How does wavelength change 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 surfaces reflect sound waves the most?

  Hard flat surfaces
• What is the result of sound reflecting off surfaces?

  It creates 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 ear?

  They travel along the ear canal to the eardrum
• What does the eardrum do when sound waves hit it?

  It vibrates
• How are vibrations transmitted from the eardrum?

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

  It converts them into electrical signals
• Where do electrical signals from the cochlea go?

  Along the auditory nerve to the brain
• How does the brain interpret electrical signals from the ear?

  As sounds with varying pitches and loudness
• What is the frequency range that humans can generally hear?

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

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

  Wear and tear of the cochlea and auditory nerve
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