Auditory Perception -- Hearing

Auditory Stimulus:

sound wave:

 

e.g. stereo speaker --speaker cone moves back and forth generating air pressure changes

Properties of sound waves:

Frequency:

 

 

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• human range is 20 Hz to 20,000 Hz for sounds

 

 

Amplitude:

 

 

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Phase:

 

 

 

 

 

 

 

 

 

 

 

 

 

Complex sound waves:

• composed of a combination of different simple pure tones (sine waves)

Anatomy of the Ear:

Outer Ear:

pinna:

 

auditory canal:

 

tympanic membrane (eardrum):

 

 

 

Middle Ear: -- separates outer ear (air medium) and inner ear (liquid medium)--

• Ossicles: the 3 bones of middle ear (tiniest in human body)

1.

 

2.

 

3.

 

 

• Oval Window:

 

 

 

 

• Middle ear structures necessary in order to increase vibrations so the waves are not stopped from traveling through the liquid medium of inner ear (impedance mismatch).
  

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  • ossicles constructed in such a way that they serve as a lever--increases force of vibrations at stapes

 

• Sets of small muscles in middle ear attached to ossicles --

 

Inner Ear:

• Semicircular canals -- used for determining our orientation (discuss later), not hearing

• Cochlea - liquid filled. -- coiled up structure looking like a snail shell containing receptors

 

 

• 3 Canals in Cochlea

1. Vestibular canal (upper canal):

 

2. Tympanic Canal:

 

 

3. Cochlear Partition (duct):

 

 

 

• Organ of Corti

 

 

 

Hair Cells:

• Inner Hair Cells:

 

• Outer Hair Cells:

 

• Tip Links:

 

 

Frequency Coding:

 

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Bone Conduction of sound: alternate way of transmitting sound to inner ear

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e.g.

Sound Localization: -- how do we determine which direction a sound is coming from?

To determine if left or right:

• Interaural time difference: composed of 2 things

1. Onset difference--

 

 

 

Problem:

 

 

 

2. Phase difference --

 

 

 

• Interaural intensity (level) difference:

Problem:

 

 

 

 

To determine if up or down:

• Barn owls have best up-down sound localization of all animals

 

 

To determine how far the source of sound is away from us:

• sound level:

• Frequency: (similar to visual atmospheric perspective)

• Movement parallax: (smilar to motion parallax)

• Reflection:

  • Direct sound:

  • Indirect sound:

Other ways to resolve ambiguities in direction: (we generally don't noticeably suffer from this problem)

Auditory Disorders:

• Tinnitus:

• Presbycusis:

• Deafness:

   

  • Conduction Deafness:
    
    

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    • Hearing Aids:

   

   

   

  • Nerve Deafness:

     

     

     

     

    • Cochlear Implants: