Voice Resonance Week 3: Aerodynamics Assessment

Phonatory Aerodynamic System (PAS)

To find out if the problem is respiratory or laryngeal

Vital Capacity

The total amount of air you can produce after a deep breath in (no phonation)

Why would a patient not be within normal range for vital capacity?

They may not have enough air in their lungs or there is something wrong with the adduction of their vocal folds

Maximum Sustained Phonation

Mean airflow rate (air expelled over time)

What would be impacted if patient has a vocal nodule? 

Adduction will be impaired because the nodules would prevent full closure. 

What would happen to the vital capacity if the patient had a vocal nodule?

The amount of air would not be impacted because the lungs are ok

What would happen to the time duration if the patient had vocal nodules? 

It would be lower because air is escaping quickly due to the vocal folds not adducting fully; the voice would be breathier. 

During a Maximum Sustained Phonation task, a patient produces a very breathy voice and is only able to sustain a vowel for 7 seconds despite having normal lung capacity. What does this suggest about their vocal fold function?

This suggests incomplete vocal fold closure (likely a pathology like nodules or paralysis), causing excess air to escape and producing a breathy voice.

If a patient has a vocal nodule, explain why their Vital Capacity would remain normal but their Maximum Sustained Phonation would be reduced.

Nodules don’t affect the lungs, so Vital Capacity remains normal. However, nodules prevent full vocal fold closure, allowing air to leak and reducing the time the patient can sustain phonation.

Phonatory Quotient

Air (no voicing) divided by the time compared to Air (voiced) divided by the time (Vocal capacity divided by maximum phonation duration)

What would happen if the phonation quotient were abnormal?

If PQ is abnormal, it indicates inefficient voice production due to impaired vocal fold adduction, which impacts airflow control and voice quality; this would be a laryngeal problem (at the level of the vocal folds).

Voice Efficiency

A measure of air pressure to voicing

What info does voice efficiency give? 

Laryngeal resistance and phonation threshold pressure 

Estimated sub-glottal pressure

Depends on what the pressure is at the level of the lips (should be about the same)

What is laryngeal resistance?

A measure of how much the vocal folds resist the flow of air from the lungs during voicing.

What does high laryngeal resistance suggest?

The airway is restricted, requiring more subglottic pressure to push air through. This may indicate hyperfunction or tension in the larynx.

What does low laryngeal resistance suggest?

The vocal folds don’t close well, so air leaks through easily (can happen with vocal fold paralysis, nodules, or breathy voice disorders).

Phonation Threshold Pressure

The minimum amount of air required to initiate phonation.

A patient is asked to vary loudness during the /papal/ task but is unable to increase their loudness without phonation breaks. What does this reveal about their ability to control sub-glottal pressure?

This indicates poor sub-glottal pressure control. The patient cannot regulate airflow and pressure well enough to maintain stable phonation at different loudness levels.

Variation in SPL (sound pressure level)

Loudness change: changes in loudness shows whether a patient can change or control their sub-glottal pressure.

Compare how airflow patterns differ between a patient with no vocal fold pathology and one with vocal nodules when attempting sustained phonation.

• No pathology: Airflow is steady and efficient; phonation lasts longer.

• Nodules: Air escapes quickly due to incomplete closure, so airflow is higher and phonation duration is shorter, producing a breathy voice.

Explain why the Phonatory Quotient is a useful measure for distinguishing between respiratory versus laryngeal causes of phonation difficulties.

• If VC is low → respiratory issue.

• If VC is normal but PQ is high → laryngeal issue (e.g., incomplete adduction).