Chapter 6 Flashcards
3 categories of measuring FF and intensity
- Levels of habitual use: typical production
- Levels of maximum performance - under mechanical stress, what are the physiologic limits
- Degree of regularity - how stable is the system
Influence on mean speaking FF and range
Linguistic factors such as speech content
How is mean speaking FF and range assessed
During sustained vowel phonation, reading, or spontaneous speaking task
What is the expected Variability in mean speaking FF
Approximately 3 semitones across multiple readings
What is maximum frequency range of phonation
Span from lowest to highest frequency of which the individual is physiologically capable
Regularity of frequency and intensity
VF vibration is a quasi periodic function
there is a small amount of cycle to cycle variability
Too much variability and the sound produced is abnormal
What is perturbation?
The variability or irregularity in a system
Short term FF perturbation is jitter
What is jitter
The nonvolitional variability in FF - not intentional
Cycle to cycle variability of the duration of the period
Exists at a low level in VF vibration
Measured during sustained vowel phonation, not over the duration of a word or phrase
What is jitter ratio?
The average difference in period in
Adjacent pairs of cycles
Divided by the average period
Why divide the average difference in periods from average periods?
Removes the effect of FF from the calculation
The magnitude of jitter is dependent on frequency of phonation
Jitter percent
Same as jitter ration just turned into a percent
Jitter factor
Uses jitter ratio method but replaces period with frequency
Jitter fun facts
Not appropriate as a screening measure to distinguish normal from abnormal voices
Normal vibration will have low level of jitter
Pathological voices have a high level of jitter
Not always sensitive to therapy or surgery
What is shimmer
The short0term variability (perturbation) in the amplitude of the acoustic waveform
Shimmer in dB
Common measure
Ratio of the amplitudes of 2 adjacent cycles averaged over the length of the sample
If expressed as percent then Shimmer Percent
Amplitude perturbation quotient
Measures shimmer
Averages the amplitude over a longer number of cycles
Shimmer in diagnostics
Often used as a diagnostic criterion for abnormal voices Normal vibration
Then as a measure of treatment outcome
Cautions in measurement of shimmer
We are unable to perceptually distinguish jitter from shimmer
No direct correlation b/w jitter of shimmer and degree of voice impairment
Should not be used as a screening tool
What is mean speaking FF
The average FF we use when speaking
What is mean speaking FF range
Typical range we use when speaking
What is voice range profile?
Relationship b/w FF and intensity in a graphic display
Horizontal axis = FF
Vertical axis = intensity
Can be done using a sound level meter - at selected pitch as loud and then as soft as possible and then repeated across range
Characteristics of VRP
Area of profile
Dynamic range is reduced at extremes
Upper and lower contours tilt upward at high frequencies
Area of profile
Wider the area, the more flexible the voice
Both dynamic intensity and pith ranges are large
What does upper contour of VRP represent
Maximum intensity at each frequency
What does the lower contour of VRP represent
Minimum intensity at each frequency
Why is it difficult to increase intensity at low frequencies?
Requirement of laxness of VF to achieve slow vibration
And requirement of increased resistance to airflow to maintain subglottal pressure
Mean airflow measurement
Measured as it exits the oral and nasal cavities
Measured as the volume of air that passes a given point in mL per second
Demonstrates control of FF and SPL
Measured USA in g apneumotachograph
Too much variability to be meaningful by itself
What other measures can be used with mean airflow
Lung pressure - subglottal pressure
Vocal efficiency - glottal resistance, frequency data
Laryngeal airway resistance - intensity data
What is pneumotachography
Mouthpiece collects airflow
Connected to electronic sensor
Produces a pneumotachograh which is a measure of mean airflow
What can alter mean airflow
Air pressure
Glottal resistance
Amplitude of vocal fold vibration
Vocal fold tension
What is a key variable in regulation of intensity
Subglottal pressure
Direct measurement of lung pressure
Needle puncture through the cricothyroid
Must be done by a physician
Very uncomfortable
Estimation of lung pressure
Highly common
Clinically friendly
Estimated subglottal pressure from measures of intraoral pressure
Uses a transducer connect to a tube
Intraoral and subglottal pressure are the same in the production of /p/ due to bilabial and velopharyngeal seals
Estimation of lung pressure pros and cons
Cons: speech context is artificial, values not reflective of running speech
Pros: Non-invasive and clinically friendly