Perceptual Evaluation of Voice

Overview of Perceptual Evaluation in Voice Assessment

Perceptual evaluation is a foundational component of voice assessment, focusing on the auditory-perceptual clinical judgments of the voice's sound and function. It involves the systematic description and quantification of various vocal parameters to determine the nature and severity of a voice disorder.

Core Parameters of Perceptual Evaluation

The evaluation process focuses on five primary dimensions of the human voice:

• Pitch and Intensity: Evaluation of the fundamental frequency and the loudness of the voice.

• Quality: The overall auditory characteristic of the voice.

• Airflow and Breathing Pattern: The physiological support and aerodynamic efficiency during phonation.

• Resonance: The balance of sound energy through the oral and nasal cavities.

• Overall Severity: A global measurement of the degree of vocal abnormality.

Pitch and Intensity Metrics

Clinical observation of pitch and intensity determines if these parameters are Within Normal Limits (WNL), Increased, or Decreased relative to the speaker's age, gender, and cultural background.

Assessment Methods

• Perceptual: Subjective auditory judgment by the clinician.

• Acoustic Measurements: Objective data collected via specialized software and hardware, such as:

  • PRAAT: A software package for speech analysis in phonetics.

  • CSL (Computerized Speech Lab): A hardware/software system for speech analysis and research.

Vocal Quality Characteristics

Vocal quality answers the question: "What does the voice sound like?" There are four main qualities identified in perceptual assessment, categorized by their underlying physiological manifestations:

• Rough: Characterized by a raspy, harsh sound. This quality is often associated with noise in the signal caused by irregular vocal fold vibration.

• Breathy: Described as a whispery or airy sound; it is indicative of hypo-function, where there is an incomplete glottal closure allowing air to escape.

• Hoarse: A combination of both rough and breathy characteristics.

• Strained: An effortful-sounding voice, typically associated with hyper-function and excessive muscular tension during phonation.

Other Observable Features

In addition to the main qualities, clinicians must document secondary features such as:

• Unstable pitch

• Pitch breaks

• Phonation breaks

• Vocal tremor

• Vocal Fry: A low-pitched, crackling sound produced by low subglottal pressure and relaxed vocal folds.

Classification of Dysphonia Severity

Severity is graded on a continuum from mild to severe based on the impact on communication and the perceivability of the abnormality.

Mild Severity

• Listener Perception: A trained listener would consider the voice abnormal, while an untrained listener might consider it unusual but still within the range of normal.

• Impact: The characteristic is not distracting, and the ability to effectively communicate is not impaired.

• Function: The dysphonia does not significantly interfere with the process of phonation.

Moderate Severity

• Listener Perception: Both trained and untrained listeners would identify the voice as abnormal.

• Impact: The characteristic is distracting at times. The ability to communicate effectively is noticeably impaired under specific circumstances.

• Function: The dysphonia interferes with phonation.

Severe Severity

• Listener Perception: Both trained and untrained listeners would consider the voice extremely abnormal.

• Impact: The vocal quality is highly distracting, and the ability to communicate is consistently affected.

• Function: The dysphonia causes phonation to be mainly absent (aphonia) or extremely effortful.

Breathing Patterns and Airflow

The assessment of respiratory support is critical for understanding the source of vocal dysfunction.

Breathing Patterns

Clinicians observe the following types of breathing:

• Clavicular: High-chest breathing characterized by the lifting of the shoulders.

• Thoracic: Mid-chest breathing.

• Diaphragmatic-Abdominal: Lower-trunk breathing, often considered the most efficient for phonation.

• Mixed: A combination of patterns.

• Coordination: Patterns are marked as either Coordinated or Uncoordinated with phonation.

Airflow Measurements

Airflow during speech is characterized as:

• Reduced

• Increased

• Adequate

Resonance and Physiological Dysfunction

Resonance involves the filtering of the sound source by the vocal tract cavities.

Nasal Resonance

Dysfunctions in nasal resonance include:

• Hyper-nasality: Excessive nasal resonance, which may or may not be accompanied by nasal emission (audible air escape through the nose).

• Hypo-nasality: A lack of appropriate nasal resonance on nasal consonants.

• Culdesac Resonance: Sound is trapped in the pharynx or nasal cavity due to an anterior obstruction.

Oral Resonance

Oral resonance is often described by the "focus" of the tone:

• Posterior Tone Focus (Back Resonance): Sound is perceived as being in the back of the throat.

• Anterior Focus: Perceived as thin or "babyish."

• Frontal Focus (Oral Resonance): This is considered the normal, desired resonance for healthy speech.

Standardized Voice Assessment Protocols

Formal scales allow for consistent documentation and comparison of voice quality.

The GRBAS Scale

Developed by the Japanese Society of Logopedics (1981), this scale assesses five parameters:

1. Grade: Overall degree of abnormality.

2. Roughness: Irregularity of vibration.

3. Breathiness: Air leakage.

4. Asthenia: Weakness or lack of power in the voice.

5. Strain: Excessive effort.

Scoring System: Uses a $4$-point scale from $0$ to $3$:

• $0 = \text{none or normal}$

• $1 = \text{slight}$

• $2 = \text{moderate}$

• $3 = \text{severe}$

• A visual analog scale may also be used for higher resolution.

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

Developed by ASHA Special Interest Division (SID) $3$ (2002), the CAPE-V is a widely used standardized tool.

Features Evaluated

• Overall Severity

• Roughness

• Breathiness

• Strain

• Pitch

• Loudness

• Other Features (e.g., Diplophonia, Fry, Falsetto, Asthenia, Aphonia, Pitch Instability, Tremor, Wet/Gurgly)

Measurement Methodology

• Visual Analog Scale: The rater places a tick mark along a line where the far left represents "normal" and the far right represents "most deviant."

• Quantification: The location of the tick mark is measured and recorded in a right-hand column.

• Consistency Markers:

  • C (Consistent): The attribute was continuously present during the tasks.

  • I (Intermittent): The attribute occurred inconsistently across or within tasks.

Assessment Tasks

1. Vowels: Sustained vowel /a/ (lax) and /i/ (tense).

2. Sentences: Six specific sentences designed to elicit different vocal behaviors:

   • Sentence A: Contains every vowel sound ("The blue spot is on the key again").

   • Sentence B: Evaluates easy voice onset ("How hard did he hit him").

   • Sentence C: Consists of all voiced sounds ("We were away a year ago").

   • Sentence D: Evaluates hard glottal attack ("We eat eggs every Easter").

   • Sentence E: Focuses on nasal sounds ("My mama makes lemon jam").

   • Sentence F: Weighted with voiceless plosives ("Peter will keep at the peak").

3. Conversational Speech: A sample of $20-30$ seconds of natural conversation.

The Towne-Heuer Passage

The Towne-Heuer Passage was specifically developed to assess hard glottal attack. It contains $100$ possible juncture-vowel occurrences and vowel onset words to identify excessive force during phonation onset.

Passage Text: "If I take a trip this August, I will probably go to Austria. Or I could go to Italy. All of the places of Europe are easy to get to by air, rail, ship or auto. Everybody I have talked to says he would like to go to Europe also."