Jitter & Shimmer: Quantitative Pillars of Vocal Fold Diagnostics
School of Speaking Team
Published on March 15, 2024
In clinical phonetics, jitter and shimmer form the core of objective voice measurement. These parameters, derived from spectrographic speech analysis, provide an indispensable window into the physiological stability of the vocal folds.
Measuring Micro-instabilities
Jitter, or frequency instability, refers to the cycle-to-cycle variations in the fundamental frequency. It is expressed as a percentage and is a direct indicator of the neuromuscular control of the musculus vocalis. Elevated jitter values often correlate with pathologies such as vocal fold nodules or paresis.
Shimmer, on the other hand, measures amplitude instability – the variation in sound intensity between successive vibrations. This parameter is particularly sensitive to asymmetry in vocal fold mass or tension, indicating organic lesions or edema.
Clinical Significance
Our algorithms, developed in collaboration with academic hospitals, calculate these parameters with an accuracy of <0.1%. This enables early detection and objective monitoring of therapy effectiveness.
From Data to Diagnosis
The School of Speaking software integrates these measurements into a comprehensive clinical dashboard. Here, jitter and shimmer are visualized alongside other quantitative voice parameters, such as harmonic-to-noise ratio (HNR) and voice range profile (VRP).
- Pre-operative evaluation: Determining baseline voice quality.
- Therapy monitoring: Objectively measuring progression in speech therapy interventions.
- Research validation: Quantifiable data for phonetic and clinical research.
This objective data forms a crucial supplement to the perceptual assessment by the speech therapist or phonetician, and minimizes subjective bias in diagnostics.