Sense of Sound (Audition)

Jun 21, 2024

Sense of Sound (Audition)

Key Requirements

  1. Stimulus
    • Sound wave: Pressurized wave needed for hearing.
  2. Receptor
    • Hair cell: Specialized receptor in the cochlea sensitive to sound waves.

Pressurized Sound Wave

  • Example: Hands clapping creates sound by compressing air molecules, leading to high and low-pressure areas.
  • Sound Wave Characteristics:
    • High and low-pressure areas form sound waves.
    • Frequency: Distance between pressures (peaks). High-frequency = closer peaks.
    • Low-frequency sound waves travel further in the cochlea.
    • Multiple frequency waves can be combined, and the ear separates the combined wave into individual frequencies.

Ear Anatomy

Outer Ear

  • Pinna: Funnels sound waves into the auditory canal.
  • External Auditory Meatus: Pathway for sound waves to reach the eardrum.

Middle Ear

  • Eardrum (Tympanic Membrane): Vibrates in response to sound waves.
  • Ossicles:
    • Malleus
    • Incus
    • Stapes: Transmit vibrations from eardrum.
  • Oval Window: Vibrates and transfers movement to the cochlea fluid.

Inner Ear

  • Cochlea: Spiral structure with fluid and hair cells.
    • Fluid Motion: Moves in response to the oval window's vibration, travels through the cochlea and returns via the round window.
    • Organ of Corti: Membrane structure inside the cochlea containing hair cells.
      • Basilar Membrane
      • Tectorial Membrane
    • Hair Cells: Convert fluid motion into electrical signals sent to the brain via the auditory nerve.

Sound Process Summary

  1. Sound waves funnel into the ear via the pinna.
  2. Waves travel through the auditory canal, hitting the eardrum.
  3. Vibrations pass through ossicles to the oval window.
  4. Oval window vibrations move cochlear fluid.
  5. Fluid movement stimulates hair cells.
  6. Hair cells send electrical signals to the brain, interpreted as sound.