Quantifying the Perceptual Quality of Strain: An Electroglottographic Analysis of Continuous Dysphonic Speech
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INTRODUCTION: Excessive vocal effort perceived as strain may involve increased vocal fold compression. Electroglottography (EGG) in principle could provide a measure of strain directly connected to oscillatory kinematics at the sound source. The utility of EGG has been limited by considerable inter- and intra-subject variability. OBJECTIVE: This work aims to (1) develop an algorithm to analyze EGG signal in continuous, dysphonic speech and (2) identify parameters that correlate with strain. METHODS: EGG signal from 8 normal speakers and 8 subjects with adductor spasmodic dysphonia (ADSD) reading two-sentence excerpts from the Rainbow Passage was processed by the new software developed in MATLAB. The contact quotient (CQ), pulse width at the 50% amplitude level (EGGW50), and various closing slope and opening slope measures were extracted from selected speech segments. Intra-subject and inter-subject comparisons were then made. RESULTS: None of the EGG parameters differed between normal and ADSD speakers. Within- subject comparison among ADSD speakers showed that the opening slope measure SO7525 distinguished between the strained and unstrained syllables. CONCLUSION: These results provide further insight into the utility and limitations of EGG. While EGG may have limited utility in inter-subject comparison, it may provide a useful objective measure of vocal strain in the same subject with variable degrees of strain or over time.