Sound waves and Hearing

• What are sound waves primarily composed of?


  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
• Why do sound waves travel faster in solids than in gases?


  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 is the relationship between speed, frequency, and wavelength in sound waves?


  If speed increases and frequency remains the same, wavelength must increase
• What happens to the wavelength of sound as it speeds up in higher density mediums?


  The wavelength gets longer
• What happens to the wavelength of sound as it 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 is the effect of hard flat surfaces on sound?


  They reflect most sound waves, creating 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 from the eardrum?

  Through the ossicles to the semicircular canals and into the cochlea
• What does the cochlea do with vibrations?


  It converts vibrations into electrical signals
• How does the brain interpret electrical signals from the cochlea?


  As sounds, with higher frequencies interpreted as higher pitches
• What is the typical range of frequencies that humans can hear?

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


  The range of hearing normally decreases due to wear and tear of the cochlea and auditory nerve
• what are sound waves


  they are longitudinal waves
• how is an oscilloscope and microphone used to display a sound wave?

  An oscilloscope connected to a microphone can be used to display a sound wave and find its frequency and amplitude.

  The greater the amplitude of a sound wave, the louder it is.

  The greater the frequency of a sound wave, the higher its pitch.

  The first sound wave shown is quiet and low pitched.

  The second sound wave shown is loud and low pitched.

  The third sound wave shown is loud and high pitched.

  
• Which property of sound waves describes the loudness of the sound?

  Amplitude

  -Higher amplitude means louder sound
• Which property of sound waves describe the pitch of

  the sound

  Frequency

  -Higher frequency means higher pitch.
• How do you measure the speed of sound in air?

  To measure the speed of sound in air, you can make a noise at a known, large distance from

  a solid wall and record the time for the echo (reflected sound) to be heard, then use

  speed = distance/time, where distance is 2 x length - taking into account the fact that the

  sound had to go there and back.