SCIENCE CHAPTER 1.1

• Pinna


  Outermost part of the ear, also called the earlobe
• Ear canal


  Part of the outer ear that further concentrates sound and directs it to the eardrum
• Eardrum


  Changes sound waves into vibrations
• Ossicles


  Three small bones in the middle ear that amplify the vibrations
• Oval window


  Passes the amplified vibrations from the ossicles to the inner ear
• Cochlea


  Contains fluid that vibrates, converting the vibrations into nerve impulses
• Auditory nerve


  Sends the nerve impulses from the cochlea to the brain
• Eustachian tube


  Balances air pressure between the middle ear and the outside environment
• Semicircular canals


  Detect head position and body balance, not involved in hearing
• Mechanism of hearing


  1. Sound enters pinna

  2. Travels through ear canal

  3. Vibrates eardrum

  4. Ossicles amplify vibrations

  5. Oval window passes vibrations to cochlea

  6. Cochlea converts vibrations to nerve impulses

  7. Auditory nerve sends impulses to brain
• Human hearing range is 20 to 20,000 Hz
• Hearing range decreases with age as eardrum elasticity decreases
• Hearing aids


  • Stethoscope
  • Hearing aid
  • Megaphone
• Causes of hearing loss


  • Infection
  • Injury
  • Aging
  • Noise exposure
• Stereophonic hearing


  Hearing with both ears to determine direction of sound
• Ear closer to sound source


  Detects sound earlier and louder
• Brain


  Interprets differences in time and loudness to determine sound direction