Speech%20Science%20XI

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Speech Science XI

• Speech Perception

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Topics

• What activity does speech perception imply?
• The physiology of hearing
• Reading BHR, Chap. 6, pp. 174-183 (The
  listener, hearing, the ear) Kent, Chap. 6, pp.
  209 ff.
• P.-M., 3.1.1-3.1.3 pp. 143-149
  (physiologische Grundlagen)

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What is Perception?

• Dictionary definition
• "The process, by which an Organism detects and
  interprets Information from the external world by
  means of the sensory receptors" (Collins English
  Dictionary)
• but also
• "Sinnliche Wahrnehmung eines Gegenstandes ohne
  bewußtes Erfassen und Identifizieren" (Duden Das
  große Wörterbuch der deutschen Sprache)

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What is Perception?

• In terms of Semiotics Perception is the
  recognition of patterns (forms) which are
  important for our (personal) life. I.e., forms
  which have a meaning for us ( Signs).
• Auditory Perception is the part of our pattern
  recognition mechanism dealing with acoustic
  input.
• What other perception mechanisms do we have?
• Speech perception is the aspect of our auditory
  perception which identifies the patterns which
  are relevant to speech in the (often mixed-up)
  acoustic signals which reach our ears.
• Are there other auditory perception mechanisms?

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Auditory Physiology

• All auditory perception is served by the same
  input channel at the auditory periphery
• The outer ear (receives the acoustic signal and
  transforms it to mechanical vibrations)
• The middle ear - strengthens the mechanical
  signal and transfers it to
• The inner ear, which transforms the mechanical
  signal to an electric signal (nerve impulses
  which travel to the brain).
• Audition is the term for these peripheral
  processes

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Anatomy of the Ear
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Outer Ear

• The part of the outer ear we can see is called
  pinna or auricle
• The auditory channel or external auditory
  meatus leads from the outside to the middle ear.
• It is a tube with a diameter of about 0.6 cm and
  a length of between 2.5 and 3 cm.
• This acts as a resonator for frequencies around
  3 kHz. (they are heard as louder)
• The ear drum is a membrane that separates the
  outer ear from the middle ear.
• The acoustic signal causes the membrane to
  vibrate.

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Eardrum

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Middle Ear 1
Middle Ear
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Middle Ear 2
Malleus
The bones in the human ear are the smallest
bonesin the body The hammer (Malleus)5.5
mm The anvil (Incus)5 mm The footplateof the
stirrup (Stapes)3.2 x 1.4 mm
Incus
Stapes
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Middle ear amplification
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Inner Ear
The inner ear has twofunctional componentsThe
vestibular systemfor balance (the semi-circular
canals) and theauditory system
(thecochlear). The cochlear is
dividedlengthways by two mem-branes into three
sectionsThe scala vestibuli, scalamedia and
scala tympani. The membrane of the ovalwindow
vibrates with thestapes and send waves down the
s.vestibuli. Atthe end of the s.vestibuli,they
pass into the s. tympanivia the helicotrema, and
are damped by the roundwindow
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Inner Ear 2
Scala tympani
Scala media
Scala vestibuli
Travelling waves in the scalavestibuli make the
Reissnersmembrane vibrate, transferringvibratio
ns to the Organ of Corti on the Basilar
membrane. The Organ of Corti has finehair cells
which, when disturbedby the vibrations, produce
smallelectrical discharges. This is the stage
at which theoriginally acoustic signal enters
the nerve system.The electrical discharges from
the hair cells transfer to theauditory nerve
and are carriedto the brain.
Above Section through the cochlear showingthe
three scalae. Below a magnified cross sectionat
one point in the cochlear.
Reissners membrane
Scala vestibuli
Basilarmembranewith Organof Corti
S. media
Scala tympani
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The Organ of Corti
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Travelling waves and the cochlear
The basilar membrane gets wider as it spirals
from thebase at the oval window to the
helicotrema at the apex.The travelling waves
build up to maximum amplitudesat different
places along the scala vestibuli, accordingto
their component frequencies higher frequencies
closer to the base, lower frequencies closer to
the apex.
In this way, different parts of the Organ of
Corti react to different frequencies, and
different strands of the auditory nerve receive
and transport frequency-differentiated impulses.
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Travelling waves
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Movement of the Organ of Corti
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Central auditorypathways
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Frequency response in the cochlear nucleus
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Neuronal response to a dynamic signal
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Directional neurons