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What is the structure of the ear and how do they function to produce…

- - - - Contracts, reducing ossicles vibration, from damaging stimuli
    - - Keeps middle-ear pressure equal to outside atmosphere
    - - Stapes (Stirrup)
      - Incus (Anvil)
      - Malleus (Hammer)
      - Function:
        
        Amplifies sound-wave vibrations received by oval window
  - - - Scala tympany (Tympanic canal)
        
        Round window
        
        Membranous window separating canal from middle ear
        
        Lower half
      - Cochlear partition (Duci)
        
        Organ of Corti
        
        Cilia
        
        Produces electrical signals from incoming sound
        
        Basilar membrane
        
        Vibrates to incoming sound
        
        Hair cells
        
        Auditory receptors
        
        Outer cells
        
        Inner cells
        
        Tectorial membrane
        
        Extended over hair cells
        
        Separates vestibular and tympanic canal
      - Scala vestibuli (Vestibular canal)
        
        Helicotrema
        
        Opening connecting it to tympanic at apex
        
        Upper half
    - - Transduction
        
        Stapes cause pressure changes in fluid in cochlea
        
        Causes cochlear partition to move up & down
        
        Causes tectorial & basilar membrane to shift
        
        Causing inner haircells/cilia to bend
        
        Cilia convert sound vibrations into electrical signals
    - - Basilar membrane
        
        High frequencies maximally activates base of membrane
        
        Low frequencies maximally activates apex of membrane
      - Auditory masking
        
        Presence of other noises limits hearing ability
      - Timing
        
        Phase locking #
        
        Firing at the same place
        
        Temporal coding
        
        Link between sound frequency and nerve firing
    - - Conductive hearing loss
        
        Sound is blocked from sound receptors
      - Sensorineural hearing loss
        
        Presbycusis (Old hearing)
        
        Damage to haircells, auditory nerve or cortex
      - Noise-induced hearing loss
        
        Haircells degenerate due to loud noises
  - - - Picking up sound waves
      - Enhancing sound intensities through resonance
      - Protecting middle ear
    - - Vibrates from incoming sound waves
    - - Sound waves travel through here towards eardrum
    - - Helps determining location of sounds
- - - - Pressure amplitude
        
        Pressure changes in any medium produced by soundwave
      - Decibel
        
        Measure for sound pressure level
    - - Amount of repeated compression-rarefraction cycles per second
      - Measured in Hertz (Hz)
    - - Particular area of cycle wave reached at certain time
      - In phase
      - Out of phase
  - - - Fundamental frequency of tone
        
        Rate of repitition of a complex tone
      - Repeating wave form
    - - Any continuous or periodic wave form is:
        
        sum of simple set of sine waves
    - - Specturm of frequencies representing harmonic components
  - - - Increase in pressure
    - - Decrease in pressure
    - - A pattern of changes in air pressure
- - - - Same letters in different octaves
      - Fundamental frequencies are multples of each other
    - - constancy of pitch
    - - Increase in tone's fundamental frequency --> increase perceived pitch
  - - - Threshold for hearing
      - 20-20,000 Hz
  - - - Different strengths of harmonics
      - Number of harmonics
- - - - Signals from inner haircells are transmitted through auditory-nerve
      - Auditory nerve sends signal through sequence subcortical structures:
      - Sequence:
        
        Cochlear nucleus
        
        Superior olivary nuclei (Brain stem)
        
        Inferior colliculus (Midbrain)
        
        Medial geniculate nucleus (Thalamus)
        
        A1 (Temporal lobe)
    - - Begins at anterior of core & belt
        
        Expands to prefrontal cortex
      - Identifies sounds
    - - Begins at posterior of core & belt
        
        Expands to parietal & pre-frontal cortex
      - Localizes sounds
  - - - Belt
        
        Parabelt
      - A1
- - - - up - down
    - - listener - source of sound
    - - left - right
  - - - Difference in sound-pressure level reaching both ears
      - Head acts as barrier --> reducing intensity to farther ear
    - - Difference in sound reaching left & right ear
    - - Our head disrupts high-frequency sound waves
  - - - Difference in frequency distribution from different locations
    - - Poor coordination of elevation with mould in ear
      - Azimuth unaffected --> binaural cue
- - - - Sound reaches ear later/lagged
    - - Sound reaches ear immediately
  - - - Sounds at different times are likely different sources
    - - Constant/smooth sounds come from same source
    - - Likely to be from same sound source if similar
      - Distracter tones
      - Auditory segregation
        
        Ability to distinguish 2 separate sound sources
    - - Melody schema
        
        Stored representation of familiar melody
    - - A sound source is usually in one position in space