4.3 Assessment of Voice & Resonance Disorders

4.3 Assessment of Voice & Resonance Disorders

Multidisciplinary Assessment Workflow & Mandatory Protocols

Assessment of voice and resonance disorders requires a rigorous interprofessional framework. On the Praxis SLP (5331) exam, a core clinical mandate is that an Otolaryngologist (ENT) must perform a medical laryngeal examination (rigid or flexible laryngoscopy) prior to the initiation of speech-language pathology voice intervention.

Clinical Workflow Imperative:
ENT Laryngoscopic Visual Examination (Rule out Carcinoma, Dysplasia, Organic Lesions)
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SLP Comprehensive Voice & Resonance Evaluation (Perceptual, Acoustic, Aerodynamic, Imaging)
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Behavioral Voice Therapy Implementation

• Rationale: Providing voice therapy without prior ENT examination is ethically and clinically contraindicated, as behavioral therapy cannot resolve malignant laryngeal neoplasms (e.g., squamous cell carcinoma) or structural conditions requiring immediate surgical or pharmacological management.

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Subjective Auditory-Perceptual Evaluation

Auditory-perceptual assessment translates human auditory perception of voice quality into standardized clinical ratings.

Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V)

Developed by ASHA, the CAPE-V utilizes a 100-millimeter Visual Analog Scale (VAS) to rate 6 core vocal parameters across three standardized tasks (sustained vowels /a/ and /i/, sentence reading, and running speech):

1. Overall Severity: Global impression of vocal deviance.
2. Roughness: Perceived irregularity of vocal fold vibration.
3. Breathiness: Audible air leakage through an incomplete glottal seal.
4. Strain: Perceived vocal effort and hyperfunctional supraglottic adduction.
5. Pitch: Auditory perceptual correlate of fundamental frequency ($f_0$).
6. Loudness: Auditory perceptual correlate of sound pressure level (SPL).

The GRBAS Scale

The GRBAS system (Japanese Society of Logopedics and Phoniatrics) employs a 4-point ordinal scale (0 = Normal, 1 = Slight, 2 = Moderate, 3 = Severe) across 5 parameters:

• G (Grade): Overall degree of dysphonia.
• R (Roughness): Acoustic correlate of frequency/amplitude perturbation (jitter/shimmer).
• B (Breathiness): Acoustic correlate of turbulent noise and reduced HNR.
• A (Asthenia): Weakness or lack of vocal power.
• S (Strain): Excessive muscular tension and elevated subglottal pressure.

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Objective Acoustic & Aerodynamic Assessment

Objective instrumental metrics provide non-invasive, quantitative baselines for tracking vocal physiology and treatment outcomes.

Acoustic Measures & Normative Thresholds

• Fundamental Frequency ($f_0$): Average rate of vocal fold vibration. Normative averages: Adult Males = 100–120 Hz; Adult Females = 180–220 Hz; Children = 250–300 Hz.
• Jitter (Frequency Perturbation): Cycle-to-cycle variation in fundamental frequency during sustained phonation. Normative threshold: $< 1.04%$ (Elevated in vocal fold mass lesions such as nodules or polyps).
• Shimmer (Amplitude Perturbation): Cycle-to-cycle variation in peak sound amplitude during sustained phonation. Normative threshold: $< 3.81%$ (or $< 0.35\ dB)$ (Elevated in glottal incompetence and vocal fold paresis).
• Harmonics-to-Noise Ratio (HNR): Ratio of periodic harmonic vocal energy to aperiodic noise energy. Normative threshold: $> 20\ dB$. Reduced HNR indicates increased breathiness and air turbulence.
• Cepstral Peak Prominence (CPP): Prominence of the cepstral peak relative to the background spectral noise floor. CPP is the current clinical gold standard for continuous speech dysphonia analysis, as it accurately quantifies voice quality without requiring steady sustained vowels or time-domain pitch tracking.

Aerodynamic Measures & Clinical Ratios

• Maximum Phonation Time (MPT): Longest duration (in seconds) an individual can sustain phonation of /a/ on a single deep breath. Normative adult values: Males = 20–25 seconds; Females = 15–20 seconds.
• s/z Ratio: $\text{s/z ratio} = \frac{\text{Maximum duration of unvoiced /s/}}{\text{Maximum duration of voiced /z/}}$
  • Clinical Interpretation: Both phonemes require equivalent pulmonary expiratory support, but /z/ requires laryngeal vocal fold valving. A ratio $> 1.4$ strongly indicates laryngeal pathology (e.g., vocal fold nodules, polyps, papilloma, or paralysis) that impairs vocal fold vibration during voiced /z/, while unvoiced /s/ remains unaffected.
• Subglottal Pressure ($P_{\sub}$): Air pressure below the closed vocal folds required to initiate phonation (Phonation Threshold Pressure $P_{ h} \≈ 3--5\ cm H_2\O$). Hyperfunctional voice disorders exhibit elevated $P_{\sub}$.
• Mean Phonatory Airflow Rate: Average rate of air passing through the glottis during phonation (Normative range: 80 to 200 mL/s). Values $> 200\ mL/s$ indicate hypofunction/breathiness; values $< 80\ mL/s$ indicate hyperfunction/strain.

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Endoscopic & Videostroboscopic Imaging

Laryngeal Videostroboscopy utilizes a synchronized flashing light source triggered by the patient's $f_0$ to create an optical illusion of slow-motion vocal fold vibration.

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Assessment of Resonance Disorders & Velopharyngeal Function

Resonance disorders result from abnormal coupling or uncoupling of the oral, nasal, and pharyngeal cavities during speech production.

Differential Typologies of Resonance Disorders

• Hypernasality: Excessive nasal resonance during production of oral vowels and voiced consonants, caused by Velopharyngeal Insufficiency (VPI) (structural defect, e.g., uncorrected cleft palate, short soft palate) or Velopharyngeal Incompetence (neuromuscular deficit, e.g., velar paresis in dysarthria).
• Hyponasality (Denasality): Inadequate nasal resonance during production of nasal phonemes (/m, n, ŋ/), caused by physical nasal airway obstruction (e.g., severe adenoid hypertrophy, nasal polyps, deviated septum).
• Cul-de-sac Resonance: Sound energy trapped in an acoustic cavity with a restricted exit (e.g., oral cul-de-sac caused by enlarged palatine tonsils blocking the oral cavity).

Objective & Clinical Resonance Diagnostics

• Nasometry: Measures Nasalance Score: $\text{Nasalance Score} = \left(\frac{\text{Nasal acoustic energy}}{\text{Nasal acoustic energy} + \text{Oral acoustic energy}}\right) \times 100$
  • Interpretation: Oral reading passages (e.g., Rainbow Passage without nasals) should yield low nasalance ($< 15%$); scores $> 25--30%$ confirm hypernasality.
• Air Pressure-Airflow Assessment (PERCI): Quantifies velopharyngeal orifice area during high-pressure consonant production (/p, t, k/). Normal closure area is $< 2\ mm^2$; incompetent closure exceeds $10--20\ mm^2$.
• Clinical Mirror Test: Placing a cold dental mirror beneath nostrils during non-nasal production (e.g., /i, s, p/); fogging indicates velopharyngeal air leakage (hypernasality/nasal emission).