Differences of Electroglottographical Contact Quotients between Connected Speech and Sustained Phonation in Clinical Measurement of Voice

Abstract

In clinical practice, sustained phonation is mostly used for acoustic voice measurements, while perceptual evaluation is based on connected speech. Since sustained phonation could be associated with the use of the singing voice, and since vocal registers are more relevant for singing rather than speech, it is unclear if vocal registers contribute to observable vocal fold contact differences between sustained phonation and speech. Sustained phonation (vowel [a] on comfortable pitch and loudness) and connected speech (German text: Der Nordwind und die Sonne) were analyzed for 1216 subjects (426 with and 790 without dysphonia) using the Laryngograph system (combining electroglottography and audio recordings). From these samples, fundamental frequency (ƒo), contact quotient (CQ), sound pressure level (SPL) and frequency perturbation (jitter first for sustained and cFx for connected speech) were evaluated. Compared to connected speech, the values of ƒo and SPL were higher for sustained phonation. For female voices, ƒo difference was greater than for male voices. At the same time, and only for the females, CQ was lower for the sustained phonation, indicating a register difference. In order to achieve a better comparability, sustained phonation should be standardized regarding the ƒo and SPL values in correspondence to the ƒo and SPL range of reading a text. This should also reduce the risk of using a different register for different types of phonation.