Speech Science: 10

Phonatory Disorders - Chapter 5

• The presentation was designed by Michael Kiefte, PhD, and presented by Glen Nowell, MSc., SLP-Reg. on November 8, 2024.
• Determining abnormal voice involves three steps:
  • Figure out how to measure voice
  • Gather normative data
  • Compare client data to normative data
• Measurable vocal fold parameters include:
  • Vocal fold movement (visual, conductivity, aerodynamics)
  • Stability of sustained sound
  • Duration of sustained sound
  • Vocal range
  • Intensity range
  • Signal-to-noise ratio
  • Changes in these parameters over the lifespan

Analyzing Vocal Fold Movement

• Direct laryngoscopy is performed during surgery.
• Indirect laryngoscopy uses laryngeal mirrors, rigid Hopkins rods, or flexible nasopharyngeal laryngoscopies (NPLs).
• Methods for analyzing vocal fold movement also include bright light, stroboscopy, and videokymography.
• Videokymography selects a horizontal line from high-speed digital images and stacks these lines to create a picture.

Laryngeal Physiology Investigation

• Laryngeal physiology investigation involves determining location, illumination, and rapidity of vibration.
• Indirect laryngoscopy involves placing a mirror on a handle in the throat.

Laryngeal Visualization

• Direct laryngoscopy uses a laryngoscope inserted into the mouth.
• Rigid scopes (e.g., Hopkins rods) are passed through the mouth, often at 70 degrees, but can range from 0 to 90.
• Nasopharyngolaryngoscopy (NPL) uses a scope inserted through the nose.

Laryngeal Parameters for Stroboscopy

• Vocal fold edges are observed for smoothness or irregularity.
• Glottic closure patterns (degree and pattern) are examined, including extent of opening and difficulty with abduction.
• Mucosal wave presence and dynamic segments of the vocal folds are considered.
• Amplitude of vibration and phase symmetry are measured.
• Supraglottic activity (AP squeeze, medial compression of false vocal folds) is noted.
• Vertical phase symmetry differences are evaluated.

Videokymography

• Videokymography is a method to examine vocal fold vibration.

Vocal Fold Examination Value

• The examination of vocal folds can identify anatomical and physiological causes of dysphonia (e.g., paralysis, lesions).
• The condition of the mucosa (e.g., edema, erythema, dryness, stiffness, injury) is assessed.
• Signs of reflux, which can irritate the back of the vocal folds, are observed.

Simple Voice Measures

• Maximum phonation time (measured in seconds) is measured.
• Pitch range (measured in Hertz (Hz)) is assessed.
• Intensity range (measured in decibels (dB)) is analyzed.

More Sophisticated Measures

• Signal-to-noise ratio (Jitter and Shimmer) is considered.
• Cepstral Peak Prominence assesses severe vs. normal voice qualities.
• Spectrogram and long-term average spectrum are visual data for speech and voice analysis.

Changes in the Phonatory/Laryngeal System Over Time

• Infant vocal folds are 3 mm in length, mostly membranous, with a fundamental frequency (f0) of 400–600 Hz.
• Gradual vocal fold lengthening occurs in pre-teens, leading to an f0 of 230 Hz.
• Androgenic puberty modifies vocal fold parameters, increasing the anterior-posterior (AP) dimension and weight, and lengthening vocal folds (63% increase compared to estrogens, 34%).
• Androgenic changes result in a pitch drop of one octave (12 semitones), while estrogenic changes lead to a drop of 2.5 semitones.
• Adulthood is associated with ossification and deterioration of laryngeal structures, affecting speech frequencies.
• Age-related changes (e.g., presbylaryngis, presbyphonia) influence voice characteristics, including muscle mass, collagen loss, and vocal fold thinning.

Defining Voice Quality

• Singing voice registers (chest/head) and descriptors (e.g., clear, breathy, hoarse, harsh) are considered.
• Voice analysis context and how it's analyzed influences measurements.
• A universally accepted method for describing voice quality isn't found due to the complexity of variables.

Timbre

• Timbre is the unique way the vocal channel filters the voice, reflecting differences in vocal tracts as much as face shape.
• Individual differences in vocal timbre can be analogous to differences in faces observed in person vs. on a phone.
• Instruments with same pitch, like Trumpets vs. Trombones, vary in timbre due to tube differences.

Vocal Fold Vibration and Voice Quality

• Vocal fold vibration results from interaction with adduction and subglottal pressure.
• Hyperadduction leads to vocal folds that are too close together; causing a pressed or strained voice.
• Hypoadduction causes vocal folds that are too far apart and therefore the voice is breathy and noisy.

Normal Vocal Parameters (Zemlin)

• Normal vocal range for children and adults (frequencies and octaves)
• Normal maximum phonation time for children and adults.
• Normal vocal intensity/sound intensity in ranges, given fundamental frequency levels.

Registers

• Various voice registers exist in speech and singing, and these categories influence how speech is produced.
• "Pulse" is a low, creaky register often present at the end of sentences.
• "Modal" is the most common conversational register; featuring full participation of the vocal cover and body tissue.
• "Loft/Falsetto" is a higher register characterized by a longer, thinner sound with less intensity & richness.

Pulse Register

• Pulse register is characterized by a closed phase of 90% and an open phase of 10%.
• Multiphasic closure: a sequence of partial approximations and separations before full adduction.
• Temporal gap occurs after each partial closure, creating a popping, creaky sound.
• This register is commonly utilized at sentence ends.

Modal Register

• Full vocal cover and body participation is during vibration in this register.
• Highest and lowest intensity voice is included.
• The vocal tract is short, and the cover is slack.

Loft/Falsetto Register

• The higher pitch register (e.g., vocal fry).
• Features a cricothyroid-dominant, longitudinal stretch/tension mechanism.
• Vocal folds become long, stiff, thin, and sharp-edged.
• Reduced adduction leads to lower intensity, sometimes a breathy quality.
• Reduced harmonic richness.

Supplementary Diagnostic & Research Techniques

• Electromyography (EMG) is used to measure muscle activity.
• EMG electrodes are directly inserted into muscles to assess their activity.
• Contaminants from adjacent muscles are reduced in EMG recordings.

Using Different Registers

• Speaking and singing often utilise modal and falsetto registers together, with overlaps.
• Genres sometimes contain abrupt register changes (e.g., yodelling, country, pop music, classical singing).
• Classical singing training aims for imperceptible transitions between registers.

Glottal Spectrum

• The glottal spectrum is generated in active vocal fold vibration.
• Harmonics of the fundamental frequency (f0) are displayed, showing their spacing.
• Harmonic intensity changes as spoken utterances change.

Real-Time Spectrogram

• Real-time spectrograms are graphical representations of instantaneous voice characteristics, including frequency and intensity.
• Formants (cluster of energy within harmonic bands) display intensity changes.

Value of Real-Time Spectrograms

• Real-time spectrograms aid analysis of many voice and speech characteristics simultaneously.
• It displays frequency and amplitude, and identifies intensity change (darker shades = higher intensities).
• Voice characteristics like breathiness and hard/soft glottal attacks are more visible.
• Aids in vocal techniques and training for visual learners.

Acoustic Analysis

• Average fundamental frequency analysis determines whether voice is within expected range based on age and sex.
• Frequency variability (f0 SD) describes voice melody and semitone equivalent.
• Frequency range can decrease as people age, with females showing higher ranges than males (possibly social).
• Maximum phonational frequency is measured; covering speech ranges of different registers (excluding pulse) and potentially dropping over time.

Voice Range Profile

• Voice range profiles map out voice intensity and frequency range, creating a cigar-like shape tilted upward.
• The lowest frequencies have limited intensity, while mid-range has a larger intensity range.
• The highest frequencies also have a small intensity range.

Acoustic Analysis (Waveforms)

• Waveforms show the amplitude variation via medial compression and release of subglottal pressure.
• Speakers often adjust vocal range via pressure, which reflects as variance in sound waves.
• Sound pressure levels (SPL) of conversational speech frequently fall in a range of 60 to 80 dB.

Perturbation Measures

• Perturbation measures (jitter, shimmer) measure the periodicity of vocal fold vibration, analyzing cycle-to-cycle differences.

Problems with Perturbation Measures

• Measuring perturbation effectively critically depends on a "good enough" baseline.
• Some voice disorders (e.g., diplophonia) don't allow usable perturbation measurements.
• Different programs use different algorithms, and intensity/recording quality strongly influences measurements.

Noise Measures (Harmonics-to-Noise Ratio, HNR; Noise-to-Harmonics Ratio, NHR)

• HNR is better when higher; showing a clearer fundamental frequency (F0) that is less noisy.
• Lower NHR shows less noise, therefore a stronger signal is present.
• Some irregularities in vibration or excessive escape of air can cause noise.
• HNR is measured using a formula involving logarithms and is often included in assessments of vocal health.

Open & Speed Quotients

• open quotient (OQ) reflects the time the glottis is open.
• closed quotient (CQ) reflects the time the glottis is closed.
• Speed quotient (SQ) relates abduction to adduction, and the time taken for vocal fold closure.

Electroglottography (eG)

• Laryngography/eG measures conductance changes across the thyroid, producing an Lx waveform that changes from weak to strong signaling.
• Each component of voice creation is directly reflected in eG readings; specifically concerning the moment vocal folds begin to touch.
• Various aspects of voice qualities (e.g., modal, falsetto, pulse, breathy voice) are reflected in the eG.

Why Use Acoustic and Visual Measures of Phonatory Function

• Baseline data measurement aids comparison of progress and ultimate outcomes.
• The data is helpful in therapeutic intervention and aids patient satisfaction.
• Subtle problems not detectable through hearing can be noted via these measures.
• The auditory measurements aid in better identification of potential problems.
• These measures validate perceived judgements.

Abnormal Voice Qualities

• Dysphonia encompasses deviant qualities, pitches, and loudness.
• Potential reasons for changes in voice qualities are various; from underlying vibratory patterns to causes of vocal problems.
• Descriptive terms of dysphonia, e.g., hoarse, harsh, strident, pressed, nasally, tinny, breathy, or excessively high/low or unpleasant are used.
• Voiced sounds are not always easily measured nor do they accurately reflect conditions and can be difficult to differentiate from some other sounds like a "normal" sound.
• Issues with the airway or voice can be observed and assessed via visuals, recordings, and measurement devices during treatment.

Breathy Voice

• Breathy voice characteristics are observed as decreased harmonic strength and increased high-frequency aperiodic energy.
• Poor voice efficiency and reduced dB levels are related to air loss.
• Some languages use variations in speech production to distinguish between similar sounds.
• Organic issues (e.g., vocal fold paralysis) & functional voice disorders often cause a breathy voice.

Rough/Hoarse Voice

• Rough or hoarse voice is identified via spectral noise during vocal vibration and turbulence (flow) via an opening and closing process.
• Rough/hoarse voice can result from functional voice disorders, lesions, or laryngitis, even cancer.

Measuring Characteristics of Populations

• Expected measures are observed amongst patients for several conditions that can vary in degree of severity.
• Conditions like Parkinson's, spasmodic dysphonia, benign vocal fold lesions, and unilateral vocal fold paralysis/paresis have characteristic abnormalities.

Acoustics of Rough/Hoarse Voice

• Inflammation or irritation of the vocal folds is often asymmetrical.
• Vocal fold inflammation may alter mucosal wave vibration, affecting periodicity.
• Aperiodicity is often observed in lower frequency sounds (below 1000 Hz).

Categories of Voice Disorders

• Voice disorders are categorized in neurogenic, psychogenic, functional, or organic/traumatic causes.

Neurogenic Voice Disorders

• Central or peripheral nerve problems related to the voice can be progressive and affect speech, voice, and swallowing.
• Disorders like ALS may aid in the identification of underlying issues impacting multiple body systems.

Classification of Neurogenic Voice Disorders

• Adduction/abduction issues (e.g., hypoadduction or hyperadduction).
• Phonatory stability, including short-term and long-term considerations affecting voice quality.
• Phonatory incoordination.
• Mixed disorders (e.g., cerebellar ataxia, multiple sclerosis, ALS).

Psychogenic Voice Disorders

• Emotional conditions may underlie voice disorders.
• Psychosocial issues can contribute to voice problems.
• Disorders may show up in aphonia as a result of stressors or trauma.

Organic/Traumatic Voice Disorders

• Phonatory or non-phonatory problems may result from misuse, abuse, traumatic injury, or medical reasons.

Benign Midcord Lesions (Nodules) and Papillomas

• Vocal fold images can be observed that are consistent with benign nodules and papillomas.

EGG Cooperation and Perturbation Measures

• EGG can accurately measure F0, HNR, jitter, and shimmer which show vocal fold vibration characteristics.
• Perturbation measures are used to predict normalcy/abnormalities in intensity and pitch range related to breathiness, diplophony, and other factors.

This quiz covers Chapter 5 on phonatory disorders, focusing on methods for determining abnormal voice and analyzing vocal fold movement. You'll explore various techniques for measuring vocal parameters, including laryngoscopy and videokymography. Test your understanding of the concepts presented by Michael Kiefte and Glen Nowell.