Sound Waves & Hearing

• What are sound waves essentially described as?

  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
• Why can't sound travel through a vacuum?

  There are no particles to vibrate
• What happens to sound waves when they move 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 stays the same
• What happens to the wavelength as sound speeds up in higher density mediums?

  The wavelength gets longer
• What happens to the wavelength as sound slows down in low density materials?

  The wavelength gets shorter
• How can sound be refracted?

  It changes speed when moving between mediums
• What surfaces reflect sound waves the most?

  Hard flat surfaces
• What is an echo?

  A reflection of sound waves
• 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 vibrate the eardrum
• 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 volumes
• What frequency range can humans generally hear?

  20 hertz to 20,000 hertz
• What causes the decrease in hearing range as people age?

  Wear and tear of cochlea and auditory nerve
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• How does age affect human hearing?

  Hearing range typically decreases with age