Transfer function of Brazilian Portuguese oral vowels: a comparative acoustic analysis

The vocal tract transfers its characteristics onto the sounds produced at the glottis, depending on its tridimensional configuration. AIM: this study aims to determine which of the seven oral vowels in Brazilian Portuguese is acoustically less impacted by changes to the vocal tract. MATERIALS AND METHOD: this is a cross-sectional prospective study. Twenty-three males and 23 females with ages ranging between 20 and 45 years (mean values of 28.95 and 29.79 years respectively) were enrolled in the study; none had voice complaints and their voices were normal under perceptive-auditory evaluation. Three-hundred and twenty-two sustained vocal emissions were digitized and acoustically analyzed by three computer programs combined. Results were compared against the distribution of resonance frequencies in a straight tube with one end sealed. RESULTS: statistical analysis showed that vowel /ε/ was significantly different when compared to the other vowels, with higher mean harmonic values and lower standard deviation for both genders. CONCLUSION: in BrazilianP ortuguese, vowel /ε/ is less impacted by changes to the vocal tract and is significantly less attenuated in both genders. The inclusion of this vowel in voice assessment standard protocols may contribute to improve the quality of the information obtained as a result of quantitative spectrographic and acoustic tests.