Measurement of Articulatory Activity

• Measurement of Articulatory Activity


  • Visual
  • Aerodynamic
  • Electrical
  • Acoustic
• Measuring Articulatory Function


  1. Can look at function on number of different levels

  2. Ear great first tool, but ...

  3. Visualization (direct or indirect) of articulator movements

  4. Aerodynamic measurements

  5. Electrical measurements

  6. Acoustics
• Visual


  • Lateral Still X-ray
  • Videofluoroscopy
  • Magnetic Resonance Imaging (MRI)
  • Ultrasound
  • Phototransduction
  • Endoscopy

  
• Aerodynamic


  • Oral + Nasal Airflow
  • Nasal Airflow
  • VP Orifice Area

  
• Electrical measurements

  
  

  Positional

  • Electromyography
  • Strain Gauge
  • Electropalatography
  • Electromagnetic articulography (EMA)

  Compressive

  • Velar Closure Force (Force Bulb)
• Nasometry

  • Measures relative acoustic output of nasal and oral cavities, assess velopharyngeal function, calculate nasalance score, looking for hypernasality
• Acoustics provides a treasure of information about articulation
• Acoustics can be used by itself or as an aid for transcription
• Acoustics is more objective than auditory perception
• Acoustic measures


  • Nasalence
  • Formants
  • Center of [spectral] gravity (CoG)
  • Locus F2
  • Voice onset time (VOT)
  • Durations of segments or transitions
  • Variability/stability
  • Coarticulation
• Acoustics is easy and cheap
• Lateral still x-ray: Single shot image of vocal tract in sagittal plane
• Lateral Still X-Ray Issues: Invasive, static, 2D
• Videofluoroscopy: Motion picture X-ray, shows structures in motion, can make timing measurements, rarely used except for swallowing studies
• Motion picture x-ray issues: invasive, 2D, not very good edge detail
• MRI is good for identifying edges and soft tissue detail, real-time MRI makes it possible to study speech production movements
• MRI issues: Invasive, restricted to supine position, substantial background noise
• Ultrasound: Becoming common as visual biofeedback in treatment
• Ultrasound


  Use high frequency sound waves to map position and movement of internal structures
• Ultrasound procedure


  1. Combined sound generator-receiver placed against skin

  2. Signal directed toward area of interest (tongue or pharynx)

  3. High-frequency signal travels through tissue

  4. Signal bounces back when it hits air, showing outline of tongue or pharyngeal wall
• Ultrasound


  • Good for identifying surfaces of articulators
  • Used to visualize tongue contours
  • May also be used to transduce lateral pharyngeal wall movement, using sensors on opposite sides of neck instead of under the jaw
  • Becoming common as visual biofeedback in treatment
• Phototransduction is used to assess the VP mechanism, gives information from opening to contact
• Phototransduction involves the detection of light passing through the VP port as it opens and closes
• Phototransduction is mostly used for research
• Endoscopy: Flexible fiberscope passed through nasal passage, the most common tool for clinical visual observation, allows direct visualization of nasal cavity and soft palate and pharyngeal walls
• Aerodynamic measurements are made using a pneumotachograph and a pressure transducer
• Oral + Nasal airflow measurement: Assess respiratory health, uses face mask
• Nasal airflow measurement: Assess airway resistance of nasal passage, nose mask
• Orifice area: Nasal airflow sensed through one nostril, indirect measurement
• Electrical measurements measure muscle activation, VP closure force, articulator positions
• Electromyography: Can be applied to any system controlled by muscle contraction, used for study of facial, soft palate muscles, not typically used for tongue
• Velar Closure Force (Force Bulb): Measures tightness of seal by measuring compressive force exerted by the velum on the posterior pharyngeal wall, provides information after closure, used in research
• Strain Gauge: Standard for transducing structural movement, especially useful for lip and jaw, allows subject to speak normally
• Electropalatography: Monitors timing and location of contact between tongue and hard palate during speech, custom-made artificial palate is fit to speaker, tongue contact with electrodes sends electronic signals to processing unit
• Electromagnetic articulography (EMA): Track flesh points inside and outside vocal tract, gives position over time in saggital plane
• • Aerodynamic measurements are primarily of pressures and airflows, though the VP orifice area can be calculated from aerodynamic measurements.
• • Electrical measurements include EMG measurement of many of the articulatory muscles (not the intrinsic tongue muscles) as well as positional measurements of the articulators.