Quantifying aberrant phonation using approximate entropy in electrolaryngography

Vocal fold vibration during vowel phonation can be used to characterise voice quality. This vibration can be measured using a laryngograph, which produces a waveform of highly correlated trans-larynx impedance variations, collectively termed the electroglottogram (EGG). Using approximate entropy (ApEn) in the EGG spectral domain, earlier work has been able to explain the meaning of “voice normality” and also to begin quantifying the impact that radiotherapy treatment has on the voicing of larynx cancer patients. In this paper ApEn is used to quantify pathological voicing in radiotherapy patients using the EGG in the time domain. Since ApEn is a viable single figure of merit, it has the potential to make assessment of aberrant voicing both more concise and objective than the subjective analysis adopted by speech and language therapists (SALTs).