Sound waves & Hearing

• What are sound waves primarily described as?

  Vibrations that pass through the molecules of a medium
• How do sound waves travel through materials?

  They travel as a series of compressions and rarefactions
• What are compressions in sound waves?

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

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

  By causing particles inside the solid to vibrate
• What happens when vibrating particles collide with their neighbors?

  The vibrations are passed on to the neighboring particles
• Why does sound travel faster in solids than in liquids?

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

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

  The frequency does not change
• What does the equation speed = frequency × wavelength imply when speed increases?

  If speed increases and frequency remains the same, the wavelength must increase
• 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?

  Sound can be refracted when it changes speed as it moves from one medium to another
• What surfaces reflect sound waves the most?

  Hard flat surfaces
• What phenomenon is created by sound reflecting off surfaces?

  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 and hit the eardrum, causing it to vibrate
• How are vibrations transmitted after hitting the eardrum?

  They are transmitted along the ossicles through the semicircular canals and into the cochlea
• What does the cochlea do with the vibrations?

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

  They are sent along the auditory nerve to the brain
• How does the brain interpret the electrical signals it receives?

  It interprets them as sounds, with higher frequencies as higher pitches
• What is the general frequency range that humans can hear?

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

  The range of hearing normally decreases with age
• What is the primary reason for the decrease in hearing range as people age?

  Wear and tear of the cochlea and auditory nerve
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