M. Fuchs et al., Similarity in monozygotic twins regarding vocal performance and acoustic features and their possible clinical relevance, HNO, 48(6), 2000, pp. 462-469
Auditory similarities in voices of monozygotic twins have already been desc
ribed in the literature. However, is there a clinical relevance! Thus, the
present study was designed to identify parameters of vocal performance and
acoustic features which are significantly more similar in monozygotic twins
than in non-related persons. In our hypothesis, comparable prerequisites f
or an increased vocal load in a profession or in an artistic education of t
he voice could be due to these similarities. We compared intra-pair differe
nces with data from a control group. Moreover,we examined the correlation o
f intra-pair differences with the age of the monozygotic twins. A greater d
ifference in older twin pairs than in younger pairs could show the effect o
f an exogene influence. In addition to the few phoniatric studies in twins
in the literature, we used current methods for acoustic analysis. We examin
ed seven parameters of vocal performance and three acoustic features in 31
monozygotic twin pairs (median age 36 years, range 18-75 years) and compare
d them with 30 control group pairs, which consisted of non-related persons
of the same age and sex, newly combined from the group of monozygotic twins
("statistical twins"). We found significant differences in seven of ten pa
rameters (vocal range, highest and lowest vocal fundamental frequency,funda
mental speaking frequency, maximum voice intensity, number of partials, vib
rate of intensity; U-test by Mann-Whitney). No correlation of the differenc
es of the identical twins with age was found in the examined parameters. Th
e voices of identical twins are significantly more similar than those of no
n-related persons regarding the above mentioned features. Thus, the suitabi
lity of the voices of monozygotic twins for professions with a high demand
on voice is comparable. Results of the group comparison correlate largely w
ith the literature. The missing correlation with age could be due to the fa
ct that the environmental effects were not measurable, and/or the developme
nt of the voice is more influenced by genetic effects.