Maximum Phonation Time, Maximum Expiration Time, and the s/z ratio in twins


Objective: The purpose of this study was to determine whether monozygotic (MZ) and dizygotic (DZ) twins perform differently in the following measures: maximum phonation time (MPT), Maximum Expiration Time (MET) and the s/z ratio.
Methods: Twenty-eight healthy male adults participated in this investigation: 10 pairs of MZ twins and 4 pairs of DZ twins. They were all native speakers of Standard Peninsular Spanish, recorded during 2012. Subjects were asked to sustain (1) /a/ three times and (2) /s/ also three times. In both cases, they performed this task at a comfortable pitch and loudness after maximum inhalation. All /a/ and /s/ tokens were manually labelled in Praat. Their durations were calculated and extracted with a script. MPT and MET were defined as the maximum duration of /a/ and /s/. For the calculation of the s/z ratio, /a/ substitutes /z/, as in Spanish the phoneme /z/ does not exist.
Results. Preliminary results suggest that MPT is longer in the cohort of MZ twins than in DZ twins while MET values are very similar. Consequently, the s/z ratio in MZ twins is lower than in DZ twins. However, when considering the Euclidean Distances of s/z ratios in intra-twin comparisons, values are very similar.
Conclusions. Results need to be examined in view of each subject’s anamnesis to detect possible outliers. An increased sample size would also be required in order to determine whether respiratory and glottal efficiency can be influenced by genetic factors. This could be useful to understand more about how a highly infectious respiratory disease such as COVID-19 affects different people.

The Voice Foundation’s 50th Annual Symposium: Care of the Professional Voice
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