Assessment of Voice Quality in Monozygotic Twins: Qualitative and Quantitative Measures

Abstract

Voice quality is the multidimensional vocal attribute, covering both laryngeal and supra laryngeal aspect. It is generally accepted that the physical characteristics of the laryngeal mechanism and vocal mechanism are genetically determined. It may be hypothesized that monozygotic (MZ) twins voice quality sound similar to certain degree. To measure the voice quality qualitative and the quantitative assessments can be used. The present study investigated MZ twins voice quality using Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) as qualitative and Dysphonia Severity Index (DSI) as a quantitative measure and compared both the voice quality measurements. Twenty pairs (6 M pair, 14 F pair) of MZ twins in the age range of 18 to 25 years were participated. Phonation of a, i, and u were recorded 3 times at comfortable pitch and loudness using Sony mini digital recorder. Five speech-language pathologists carried out qualitative assessment. CSL 4500 was used to measure the frequency and intensity parameters and jitter values. Correlation coefficient was significant (p< 0.01) for all the parameters except strain, loudness, low-Intensity and jitter, and paired‘t’ test showed no significant difference between twins for any of the parameters. Gender difference was significant for maximum phonation time and high fundamental frequency. This difference was attributed to anatomy and physiological variation among gender. High negative Correlation coefficient (r = - 0.78) was found between qualitative and quantitative measurements. DSI also showed good coefficient value with roughness and breathiness of CAPE-V. In conclusion, voice quality of monozygotic twins was similar in many of the parameters of qualitative and quantitative measures. Further investigation with a large scale of sample and confirmed genetic analysis is warranted.