Instrumental Assessments in Voice Disorders

Instrumental assessments (aerodynamic, acoustic, and source) document voice disorder and the status of the voice production system (respiratory, source, supraglottal tract).
Vocal function studies aid in defining treatment goals and providing visual feedback during voice therapy, and repeated testing monitors treatment/disease progression.
Instrumental tests, although providing numerical data, are not entirely objective; examiner influence and factors beyond laryngeal status can impact results.
Standardized protocols, recording procedures, patient instructions, and environments maximize usefulness of vocal function testing.
No single measure fully explains voice production or individual variations; clinicians select subsets based on their approach and training.

Respiratory Measures

Comprehensive pulmonary function tests are often unnecessary for voice-related concerns.
Useful measures for describing voice disorders and treatment planning include maximum inspiratory/expiratory pressures, vital capacity, and the percentage of vital capacity used during speech initiation/termination.

Source Measures

The voice source results from vocal fold vibration (glottal area) and interaction with subglottal and supraglottal pressures (glottal flow).
Electroglottography (EGG) measures electrical conductance across the neck during vocal fold vibration.
EGG shows positive slope during vocal fold contact and negative slope during separation, but it's relative.
Inverse filtering removes vocal tract effects (formants) from acoustic/aerodynamic waveforms to isolate glottal flow.
Several measures (e.g., skewing, open quotient) can be derived, but standardization and validation are challenges.

Aerodynamic Measures

Measuring air pressure and airflow provides valuable information about voice production.
Intraoral air pressure during voiceless consonants (e.g., p) estimates subglottal pressure.
Factors like loudness, age, gender, and consonant affect measurements.
Phonation threshold pressure (PTP)—the subglottal pressure needed to initiate vocal fold vibration—is sensitive to vocal fold viscoelasticity, useful for observing changes due to factors like dehydration/fatigue/warm-up.
Airflow (volume/time) is influenced by factors such as gender, age, fundamental frequency, and intensity. High values suggest poor glottal closure.
Laryngeal airway resistance is the ratio of translaryngeal air pressure to airflow. Higher resistance can point to increased intensity, longer glottal closure, or stronger closure force.
Maximum phonation time (MPT), while commonly used, is influenced by several factors, demonstrating poor validity/reliability.

Measures of Velopharyngeal Function

Inadequate velopharyngeal function results in nasal air emission & weak pressure consonants.
Nasal airflow and intraoral air pressure measurements assess velopharyngeal competence.
Oronasal resonance balance (e.g., hypernasality, hyponasality) can be assessed acoustically using instruments like the Nasometer.
Nasalance (ratio of nasal to total sound energy) is a measure, but correlation with perceived hypernasality is not always high; it often used in binary terms (normal/abnormal).

Acoustic Voice Measures

Acoustic data yield information about pitch, loudness, and voice quality.
High-quality equipment, a quiet environment, consistent mouth-to-microphone distance, and standard instructions are crucial.
Interpretation considers age, gender, interactions between parameters, and representativeness of typical voice.

Frequency

Fundamental frequency (F0) is the number of cycles per second in the waveform.
Pitch is the perceptual correlate of F0; changes in F0 or limited range may signal voice disorders.
Normative values vary based on intensity, speech samples, vowel type, age, and gender.

Intensity

Intensity (sound pressure level in dB SPL) is correlated with loudness, influenced by frequency, vowel, speech sample, equipment, distance, and ambient noise.
Common measures include average speaking intensity, minimum intensity, and maximum intensity.

Voice Range Profile (Phonetogram)

A phonetogram graphs intensity versus frequency, illustrating vocal range. Useful for tracking change & identifying difficulties with pitch/loudness combinations (e.g., trouble singing quietly).

Perturbation and Noise Measures

Perturbation (e.g., jitter, shimmer) measures voice quality variability (roughness, breathiness, strain). However; meaningful changes require a significant shift in these measures.
These measures are not always reliably indicative of voice quality and usually not included in current best practice standards for acoustic analysis.

Spectral and Cepstral Assessments

Spectrograms display the time-varying frequencies (bandwidth changes highlight formants or source components), while a long-term/average spectrum provides energy across all frequencies.
Cepstral peak prominence (CPP) measures signal periodicity without relying on fundamental frequency; reflects harmonic regularity and perceived voice quality.

Diagnostic Therapy (Probe Therapy)

Diagnostic therapy (probe therapy) assesses voice quality modifications in response to probes to guide treatment decisions/diagnoses.

Introduction to Therapy for Voice and Laryngeal Disorders

Speech-language pathologists guide patients to a healthy voice production mechanism, improving quality/loudness, communication, and vocal health.
Therapy is generally short-term (1-8 sessions), more effective with early improvement potential.
Indirect therapy (counseling) focuses on vocal hygiene and phonotrauma reduction.
Direct therapy focuses on voice production techniques, often more beneficial than only vocal hygiene routines.

General Comments on Voice Therapy Techniques

Therapy techniques vary depending on patient needs/strengths and clinician training.
Techniques often target resonance, laryngeal, and respiratory systems, utilizing varied approaches.

Supraglottal Vocal Tract

"Resonant" or "semioccluded vocal tract" techniques modify the vocal tract shape (length, diameter) through laryngeal height, lip rounding, and constrictions/expansions of the supraglottal structures, influencing vocal qualities and harmonic structure.
Patients learn to feel vibration in the mouth/face and to decrease laryngeal tension.
External devices (straws, kazoos) may initially aid in achieving the perceptual target.

Laryngeal Muscle Balance

Manual tension reduction and massage target extrinsic laryngeal and strap muscles to interrupt disordered voicing patterns & improve voice quality.

Coordination of Respiratory-Laryngeal Valving

Patients may misuse respiration/laryngeal valving (e.g., insufficient/excessive airflow, poor adduction/closure).
Strategies (e.g., stretch-and-flow) focus on coordinated airflow management during voiceless/voiced tasks, decreased throat constriction, and vocal function exercises-

Breath

Appropriate inhalation timing and breath groups.
Vital capacity targets during speech initiation/termination are often 60%/40%.
Patients who talk loudly might need instructions for larger lung volumes and muscular effort to resist recoil.
The Accent Method coordinates abdominal movement with sound production for holistic voice adjustments.

Posture and Alignment

Addresses musculoskeletal issues that contribute to voice problems (e.g., jaw jut, neck alignment, shoulder position).

Additional Considerations

Techniques addressing age-related dysphonia are explored.
Voice therapy tailored to professional speakers/singers involves coordination with respective professionals.
Therapy for transgender communication addresses modifications beyond pitch modification.

Therapy for Laryngeal Airway Disorders

Speech-language pathologists also address chronic cough and paradoxical vocal fold motion.
Chronic cough therapy is similar to voice therapy but emphasizes environmental modifications (hydration, moisture, irritants reduction).
Paradoxical vocal fold motion therapies incorporate medical assessment, education, environmental/psychological control strategies, and breathing/relaxation programs.