Hearing

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Hearing

• What is a sound?
• Intensity Frequency

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Hearing

• Outer Ear

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Hearing

• Middle Ear
• The bones are designed to transfer an air
  pressure wave into a fluid pressure wave. This
  requires 20x amplification

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Hearing

• Attenuation Reflex
• Small muscles respond when sound is too loud
  greater attenuation at low frequencies no
  protection from sudden loud sounds protects you
  from your own voice

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Hearing

• Cochlea (Snail)

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Hearing

• Cochlea (Snail)
• Three chambers Scala Vestibuli Scala Media
  Scala Tympani
• Organ of Corti

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Hearing

• Organ of Corti
• Basilar Membrane
• Hair Cells
• Tectorial Membrane

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Hearing

• Response of the Basilar Membrane

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Hearing

• Response of the Basilar Membrane

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Hearing

• Response of the Basilar Membrane

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Hearing

• Organ of Corti

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Hearing

• Organ of Corti

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Hearing

• Organ of Corti

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Hearing

• Cilia

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Hearing

• Cilia

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Hearing

• Cilia

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Hearing

• Cilia

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Hearing

• Amplification by the Outer Hair Cells

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Hearing

• Pathways in the Nervous System

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Hearing

• Processing Sound Frequency
• The Basilar Membrane

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Hearing

• Processing Sound Frequency
• The Basilar Membrane

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Hearing

• Processing Sound Frequency
• The Basilar Membrane

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Hearing

• Processing Sound Frequency
• The Basilar Membrane

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Hearing

• Processing Sound Frequency
• Response of Hair Cells to fluctuations in the
  Basilar Membrane

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Hearing

• Processing Sound Frequency
• Characteristic Frequency of an auditory neuron

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Hearing

• Processing Sound Frequency
• The Auditory Nerve

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Hearing

• Processing Sound Frequency
• The timing of neural firing and phase locking

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Hearing

• Processing Sound Frequency
• Tonotopic structure of the Auditory Nerve

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Hearing

• Processing Sound Frequency in the Cochlea
• 1. Sound pressure is communicated to the cochlea
• 2. The basilar membrane vibrates consistent with
  the composite frequencies in the sound
• 3. Outer hair cell cilia bend with the sound
  pressure wave
• 4. The motile response of the outer hair cells
  amplifies the basilar membrane response
• 5. These factors are communicated to the inner
  hair cells
• 6. Neurons respond by phase-locked firing
  patterns that convey a limited range of frequency
  response

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Hearing

• Processing Sound
• Frequency
• Cortical processing

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Hearing

• Cochlear Implants

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Hearing

• Processing Sound Frequency
• Periodicity or Virtual Pitch a and c below are
  perceived almost the same

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Hearing

• Processing Sound Frequency
• Pitch Streaming