Instrumental Assessment of Voice Flashcards
Instrumental Measurements of Voice: Clinical Utility
DETECTION
– identify the existence of a voice problem
SEVERITY
– assess the severity or stage of progression of the voice
DIAGNOSIS
– identify the differential source of the voice problem
Instrumental Measures in the Voice Laboratory
- Acoustic recording and analysis
- aerodynamicassessment
- laryngealvideostroboscopy
- high speed digital imaging (HSDI)
- electroglottography
- electromyography
Acoustic Analyses
- Assess physical correlates of perceptual evaluation
- Pitch/Frequency
- Loudness/ Intensity
- Perturbation
- Noise
- Spectral/cepstral analyses
Acoustic Recording and Analysis
- Provides an imperfect, non-invasive measure of vocal function
- Can discriminate normal from pathologic voice
- Is inconsistent agreement between acoustic measures and audio-perceptual
ratings of voice quality - Can measure change in vocal production across time
=Acoustic Analyses
- Fundamental Frequency
- Intensity
- Frequency range
- Jitter/shimmer/cycle-to-cycle variability
- Noise to harmonics ratio
- Phonetogram/Voice Range Profile (frequency by intensity plots)
- Cepstral Analysis (CPP)
Routine Voice Acoustic Measures
Fundamental Frequency (F0) (1. level)
- Directly reflects the vibration rate of the vocal folds; the acoustic correlate of pitch
- Unit of measurement: Hertz (Hz) or cycles per second
- Normative data = 100-150 Hz males; 180-250 Hz females
- Know male and female F0!
- May be measured from sustained vowels, reading, or conversation
- Useful to estimate the appropriateness of F0 for sex and age and for demonstrating
pre- and post-treatment change
Frequency Variability (2. variability)
- Pitch sigma is the standard deviation of the fundamental frequency
- Assess and documents variation of F0 during speech production
- How much is the pitch changing during task or during recording in general
- Should not have a lot of variability during vowel prolongation
- Should have more variability during reading and conversational speech
- How much voice in varying in normal sample
Phonation range (3. range)
- Range of frequencies from the highest to the lowest that a patient can produce
- How much client can physically do: see what system is capable of (increase and decrease pitch as high or as low as they can with modal/falsetto pitch)
- May be expressed in Hz or semitones
- Semitones: 12 semitones make up 1 octave
- Normal young adults have about a 3-octave range; may vary with practice
- Octave = doubling of frequency
- 1 octave: 100-200 Hz, 2
octave: 200-400 Hz, etc.
Frequency Perturbation (4. perturbation) JITTER
- The change of frequency from one successive period to the next (horizontal)
- Assessing cycle to cycle variability in the voice: are cycles similar to each other
- More similar = more periodic = better quality
- Unit of measurement is jitter; several algorithms are used to extract jitter
- Normative data (normal voice) for jitter percent is less than 1.00%
- Hoarseness = will be more than 1%
- Measures MUST be made from sustained vowels ONLY: not reading or speech
- Reading and speech has frequency variability which will increase jitter score - May represent variation of vocal fold mass, tension, muscle activity, or neural activity
all of which may affect the periodicity of vocal fold vibration
Intensity (I0) (1. level)
- Directly reflects the sound pressure level (SPL) of voice; direct correlate of loudness
- Reflects vocal fold adduction
- Unit of measure is the logarithmic decibel (dB) scale
- May be measured from sustained vowels, reading, or conversation
- Useful as pre- and post-treatment measure
- Overall SPL:
- Average SPL in dB (depends on
room you are getting measures
from)
- Indication of the strength of
vocal fold vibration (Norms: 75-80
dB conversation)
Amplitude Variability (2. variability)
- Standard deviation of the SPL during connected speech
- Reflects loudness variability
- Reflects phase closure
- Sustained vowels: want variability to be minimal
- Reading and speech: will vary more
Dynamic range (3. range)
- Range of vocal intensities that a person can produce (Norms: 50-115 dB SPL)
- General range that you expect them to be in, don’t have to go to 50 and 115,
need to be within the average range (which was not specified) - Checking the loudest they can go and softest that they can go
Amplitude Perturbation (4. perturbation) SHIMMER
- Small cycle to cycle changes of the amplitude of the vocal fold signal (vertical)
- Unit of measurement is shimmer; several algorithms are used to extract shimmer
- Normative data for shimmer dB is less than .35 dB
- Measures MUST be determined from sustained vowels ONLY: not reading and
speech - May represent variation of vocal fold mass, tension, muscle activity, or neural activity
all of which may affect the amplitude of vocal fold vibration
Harmonics to Noise Ratio
- A ratio measure of the energy in the voice signal over the noise energy in the voice signal (signal they are getting should be greater than noise in the room OR the amount of “noise” occurring from vocal productions)
- Noise: breathiness, raspiness, hoarseness, roughness
- May be derived from different algorithms and expressed in various units
- Greater signal or harmonic energy in the voice reflects better voice quality
- Large noise energy represents more abnormal function
- Ideally greater than 20 dB
- Most reliable in comparison to jitter and shimmer
- Jitter and shimmer: can only get data from sustained vowel and software has
difficulty marking the beginning and end of cycles - More severe hoarseness = less reliable jitter and shimmer values
Voice Range Profile (Phonetogram)
- Plots maximum and minimum intensities (loudest/softest) for entire frequency range
- Assess F0 and intensity and individual’s minimum and maximum capabilities.
- Resulting plot is ellipsoid-shaped frequency/intensity profile and the dimensions are expressed in semitones
- Most useful in pre and post-treatment of professional voice users because it provides a thorough description of the patient’s physiologic limits of frequency and intensity
- More therapy = range increases = holes/gaps should fill, ellipsoid should increase
Spectral Analyses
- Includes spectrogram, line spectrum, cepstrum
- Useful to assess the interaction between the glottal sound source (vocal folds) and supraglottic (vocal tract) influences
Spectral Analyses: - Spectrogram
- Displays the glottal sound source and filtering characteristics across time
- Putting many photographs together (like a video)
- Both formant frequency energy (vocal tract resonance) and noise components
(aperiodicity) are presented in a 3D scale - Horizontal axis = time — vertical axis = frequency
- Lowest band = F0; formants lie above
- Gray scale (darkness) represents intensity change
- Dark gray bands = stronger formant energy
- Light gray bands =poor formant energies and nosier signal
Spectral Analyses: Line
- Fourier transformation of spectrogram (snapshot in time, like a photograph)
- Plot in the frequency domain
- Plots all harmonics/frequencies at a single time point
spectrum- Frequency on the horizontal axis, amplitude on the vertical axis
Spectral Analyses: Cepstral analyses
- Fourier transformation of the spectrum
- Emphasize peaks of the strongest harmonics, including fundamental frequency
- Cepstral peak prominence (CPP) compares the height of the cepstral peak to
the aperiodic noise in the voice - Sharper the peak, more periodic the voice (breathy → less prominent peak)
- Cepstral measures do not rely on pitch detection like perturbation measures
- Measures not dependent on identifying fundamental frequency, marking cycle
boundaries or adequate intensity - Cepstral measures have strong correlations with perceptual CAPE-V measures
- Measures of cepstral analyses
- Cepstral peak prominence (CPP) in dB
- CPPvowel: average of 3 trials: 1-second sample of steady /a/
- CPPspeech: using Rainbow Passage or CAPE-V sentences
- Normatives vary by software: Praat, SpeechTool, ADSV
Acoustic Reading Considerations
- Must be a quasi-periodic, stable sound source (GET A GOOD SAMPLE)
- Most measures are taken from the stable vowel /a/
- Get them to give you a really good ahh for 3-5 seconds - Measures must be at least 1 second in length
- Super breathy or hoarse: can get a measure with 1 second of production
- The greater the dysphonia, the less confidence in the acoustic measures (esp.
perturbation measures) - Variations in F0, I0, and vowel will affect measures
- Number of trials must be adequate to represent speech behavior
- Must attend to intrasubject variability by controlling for intensity and frequency in the
retest condition (want sample to be as controlled as possible)
Acoustic Analyses: Technology Specifications (Necessities)
- Microphone
- Omnidirectional/unidirectional, headset/handheld, 4-10 cm mouth-to-microphone
distance (want a stand for handheld microphone) - Microphone preamplifier
- Recording device
- Minimum sampling rate of ≧ 44.1 kHz
- SPL calibration using a sound level meter (C-weighted)
Testing Stimuli
Sustained vowels
- Sustain the vowel /a/ at a comfortable and constant pitch and loudness for 3-5
seconds on one breath (3 trials)
- Measures: CPP and all measures of vocal signal quality
Standard Reading Passage
- Read Rainbow Passage (adults); The trip to the Zoo (children who can read) in
comfortable pitch and loudness
- Measures: habitual vocal SPL, mean/model vocal F0, vocal F0 SD, and CPP
Loudness range
- 1. Sustain the vowel /a/ as soft as possible for at least 2 seconds without
whispering (3 trials)
- 2. Sustain the vowel /a/ as loud as possible for at least 2 seconds (3 trials)
- Measures: minimum and maximum vocal SPL
Pitch range
- 1. Sustain the vowel /a/ as a high in pitch as possible (including falsetto) for at least 2 seconds (3 trials)
- 2. Sustain the vowel /a/ as low in pitch as possible (in modal register–do NOT include fry/pulse register) for at least 2 seconds (3 trials)
- Measures: minimum and maximum vocal F0
Aerodynamic Analysis of Voice
Aerodynamicmeasurementofvoiceproduction concerns measurements of air pressures and air flows that are meaningful in clinical diagnosis and treatment. These measures may help interpret:
– valving activity of the larynx
* vocal fold structure
* vocal fold configuration
* vocal fold movement
Aerodynamic Assessment Phonatory Volume, Average Flow Rate and Subglottal Pressure
Phonatory volume: total volume of airflow measured during maximum sustained vowel production
- Average flow rate: steady vowel at normal pitch and loudness for 5-10 seconds
- Subglottal pressure: acts as a force building up below the adducted VF, rising
until it overcomes VF resistance and sets folds into oscillation
Aerodynamic Assessment
- Need a pneumotachograph for all three measurements on one instrument
- All 3 are not necessary to bill for
aerodynamic measurement
Max phonation time (MPT)
- All 3 are not necessary to bill for
- Maximum prolongation of /a/ after maximal inspiration, comfortable pitch and loudness (prior demonstration is necessary)
- 3 trials, the longest time is selected
s/z ratio - Should be able to hold /s/ and /z/ for same amount of time
- <1.2-1.4 indicative of inefficient valving
- «1.0 = repeat task
- Initially developed as a screening tool (user error, lots of variability; grain of salt)
Hand-held spirometer - Measures vital capacity (3 trials; use largest value)
- Hold it, take a deep breath, and blow (sounds kinky) - Phonation quotient (PQ): ml/s
- Largest VC (ml)/Longest MPT (sec)
- Norm PQ = 135 ml/s for males, 125 ml/s for females
Subglottal pressure screening tool - Water glass manometer test, “5 cm for 5 seconds”
- 5 cm: how much pressure we need for speech
- Measure for subglottal pressure = cm H20
Aerodynamics Info
- The vocal tract is an aerodynamic sound generator and resonator system
- Variations in the flow of air through it reflect changes in the manner of consonant and
vowel articulations - Evaluation of airflow can produce insight into speech/voice system dysfunction and
efficiency
CONSIDER
- What could increased airflow tell us about the closure of the vocal folds? - VF are not closing
- What could decreased airflow tell us? - VF tightness, compression
- What could high subglottic pressures tell us about happenings at the level of the glottis?
- High subglottal pressure: lots of compression at the VF (stiffness)
- You require more air to push VF apart which leads to increased pressure
- What disorders could this be applied to?
- If there are unstable or irregular patterns of average flow= respiratory compromise or neurologic disorders
- If there is minimal airflow rate= hyperfunctional voice or glottal fry
- High airflow rate and short vowel durations= primary glottal incompetence (VF
paralysis)
Instruments to Measure Pressure and Flow
- U tube manometer
- Wet spirometer
- Hot wire anemometer
- Pneumotachograph
- Magnetometers
Aerodynamic Recording Considerations
- Requires airtight seals around the lips or mask to face
- As natural speech as possible must be encouraged in this foreign environment
- Multiple trials are necessary to ensure a stable baseline
- Instrument calibration is required prior to each examination session
Common Aerodynamic Measures: Airflow volume
- Volume of air in the lungs available to drive the vocal folds for voice production
- Measured in liters, will vary with age/sex/size/health
Common Aerodynamic Measures: Maximum phonation time
- Maximum time that a vowel may be sustained while using maximum airflow volume
- Will vary with lung capacity, age,
sex, size, health - For therapy purposes, MPT is
calculated using vital capacity
measure
- Will vary with lung capacity, age,
Common Aerodynamic Measures: Airflow rate
- Rate at which air passes between the VF during phonation
- Airflow volume divided by MPT (volume in liters/MPT in sec)
- Measures in liters/sec, with normal rate = 80-200 ml/sec
Common Aerodynamic Measures: Subglottal Air Pressure (Psub)
- Measure of air pressure beneath the VF necessary to overcome the resistance of the approximated folds to initiate and maintain phonation
- Measured in cm/H20 with norm for conversational voice being 3-7 cm/H20
- Direct measure is necessary through needle puncture into trachea
- Intraoral pressure measures reflective of Psub (when saying /puh/)
- During the production of /p/, the
glottis is open and the lips are
closed
- For this brief period of time, the
pressure within the oral cavity
should be equal to that at the
level below the glottis (subglottal),
since pressure will tend to
equalize within a closed space
- Intraoral air pressure is
measured during a syllable
repetition task /puh/
- A tube, placed between the lips,
measures pressure within the oral
cavity during the production of
/puh/ (use to infer about Psub)- Vocal fold stiffness, hypo/hyperfunction, incomplete glottic closure will influence Psub
- High stiffness → decreased flow
→ hyperfunction or glottal fry →
higher Psub - Incomplete glottic closure →
increased flow → short vowel
duration and breathiness →
lower Psub
- High stiffness → decreased flow
- Vocal fold stiffness, hypo/hyperfunction, incomplete glottic closure will influence Psub
- Clinically, Psub correlates with the level of supraglottic structures
- Increased supraglottic hyperfunction or hyperfunction of supraglottic structures
- Increased supraglottic hyperfunction with result in increased Psub
- Estimates of subglottal pressure provide an index of glottal function
- Excessively high pressure values indicate hyperfunction while low values point to hypofunction
- Normal speakers produce pressure values of 5-8 cm/H2O, although intelligible speech can be produced with as little as 3 cm/H2O
- Think of a few voice disorders and how they would affect Psub
- Eg. vocal fold paralysis with hyperfunction, vocal fold paralysis without
hyperfunction, muscle tension dysphonia - Therapy = system relaxing more = less resistance = lower Psub
Common Aerodynamic Measures: Phonation Threshold Pressure (PTP)
- A measure of the effort needed to initiate phonation
- Theoretically, healthy VF = lower PTP
- Measure is estimated indirectly using intraoral air pressure measured at the exact moment of onset for barely audible phonation (softest voice you can get)
- Ask to start saying /puh/ at a whisper and then begin to use voice
- Speakers with vocal pathologies often require greater effort to initiate phonation
- How would nodules alter PTP? Other disorders??
- Nodes would require greater effort to bring the VF together, causing a higher phonation threshold pressure
- PTP increases with vocal fatigue due to increased effort required, people who have vocal fatigue are more likely to present with higher PTP
- Not sure what else she means by other disorders
Common Aerodynamic Measures: Laryngeal Airway Resistance (additional measures for airflow/pressure)
Measured in cm H2O/liters/sec
- Ratio of translaryngeal pressure to translaryngeal airflow is an estimate of laryngeal
airway resistance
- Index of glottal efficiency
- This is a combination measure: measures of pressure AND flow in a ratio
- Quotient of peak intraoral air pressure (form unvoiced plosive /p/) divided by the peak
flow rate (measured form a vowel) as measured from a repeated consonant vowel
syllable such as /pi/pi/pi/
- Estimates the overall resistance of the glottis and therefore the valving characteristics,
i.e. too tight (hyperfunction) , too loose (hypofunction) , normal
- Think of a few voice disorders, how would they alter LAR?
- If you have a client with muscle tone dysphonia (MTD), would you want therapy to
increase or decrease their LAR? (help me out here guys)
Laryngeal Videostroboscopy
- Two types of endoscopes for laryngeal viewing: Rigid and flexible
- Rigid endoscope: 90 or 70 degree, oral placement
- Advantages: allows close view of the larynx, larger magnification, stable lens-to-object distance- Disadvantages: sample is limited to a sustained /i/, difficulty recording with a hyperactive gag reflex, sample never fully representative of voicing during habitual speech
- Flexible endoscope: nasal placement
- Advantages: helps view larynx during connected speech tasks, allows a broader
view of the vocal tract and supraglottic region, tonsil and base of tongue region
- Disadvantages: darker image, limited by disruptive movements of the velum or
swallows, difficult to achieve a stable image at times - Videostroboscopy does three things:
- 1) Demonstrates the gross movements of the laryngeal structures
- 2) Provides immediate image of presence or absence of pathology and a
permanent visual cord - 3) Demonstrates the characteristics of vocal fold vibration and the integrity of the
mucous membrane fold covering
Principles of Stroboscopy: Talbot’s Law
- Images linger on human retina for 0.2 sec after exposure (persistence of vision)
- The eye can perceive no more than five distinct images per second
- When sequential images are produced at intervals shorter than 0.2 seconds, they
persist on the retina with successive images to produce the optical illusion of
apparent motion
Stroboscopy and Talbot’s law
- VF vibration is too rapid to be perceived by the human eye
- Strobe light flashes on the vibrating VF
- Each light pulse illuminates a point of the vibratory cycle
- Illuminated points are visually fused, providing an averaged vibratory cycle
pattern over successive cycles - When flashes are emitted at same frequency as phonation, they optically occur at
the same phase point in the successive cycles and images appear frozen - When flashes are slightly slower (2 Hz) than frequency of phonation, they
optically occur at different phase points in successive cycles yielding as
simulated slow-motion effect of the VF vibration
Instrumental Components of Stroboscopy
- rigid or flexible endoscope
- video camera
- light source: halogen and xenon (strobe light)
- digital recorder
- monitor
- printer
- computerinterface
Assessment of Laryngeal Structures: Direct Light and Strobe Light
Under halogen light/direct light/non-strobe: to assess gross structure and function
- Overall appearance and vocal fold edge
- Vocal fold mobility/arytenoid mobility
- Supraglottic activity
- Ventricular fold compression, ant/post compression; epiglottis to arytenoids - Vertical level approximation
- Modified by superior laryngeal nerve paralysis
- Modified by large mass lesions (ex. polypoid degeneration from edema)
Assessment of Laryngeal Structures: Direct Light and Strobe Light
Under stroboscopic/xenon light: to assess vibratory features
- Glottic closure: observed during vibration of the VF
- Amplitude of vibration: lateral excursion of the VF
- Mucosal wave
- May be affected by pathology, scarring, pitch, loudness, hyperfunction, anxiety, subglottic driving force - Non-vibrating portion AKA adynamic portion (due to scarring or lesion)
- Phase closure: closed/open phase timing should be equal
- Phase symmetry: mirror image
Pathologies
- Vocal fold cover: mass lesions
- Need to describe location of pathology and appearance of lesion
- Neurogenic: vocal fold paralysis
- Muscular dysfunction: muscle tension dysphonia
**
Stroboscopy Procedure
- How to get a successful stroboscopic image, recording protocol, report writing, artifacts
Visualization
- Review ENT performed videos, if you are not performing endoscopy, stroboscopy
- Various rating scales available to rate structure and function of vocal folds
- SERF, Stroboscopy rating scale, rating scale, voice-vibratory assessment with
laryngeal imaging (VALI)
High Speed Digital Imaging
- Recording in real time: 2000 or 8000 frames per second
- Not frequency dependent hence does not produce tracking errors
- Effective in visualizing VF vibratory features for highly dysphonic voices as well
- Diagnostic implications for spasmodic dysphonia and disorders that affect vocal fold pliabilty
Inverse filtering
- The sound pressure signal represents the product of the glottal resonances, vocal tract resonances, and lip radiation characteristics acting on the glottal wave (the pulsative flow of air through the glottis)
- Non-laryngeal acoustics are subtracted from the radiated acoustic signal, restoring it to a simpler form that represents what the larynx produced
- The glottal volume velocity waveform is produced by glottal inverse filtering
Other physiologic measures of vocal function: Electroglottography (EGG)
- Using electrical current passing through the neck
- EEG measures vocal fold contact across time
Other physiologic measures of vocal function: Electromyography (EMG)
- The only direct measure of laryngeal function
- Needle electrodes are inserted into the laryngeal muscles and the pattern
of electrical activity is measured