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

Maria Inês Rebelo Gonçalves,Paulo Augusto De Lima Pontes,Vanessa Pedrosa Vieira,Antônio Augusto De Lima Pontes,Daniella Curcio,Noemi Grigoletto De Biase

doi:10.1016/s1808-8694(15)30518-8

Abstract

SummaryThe vocal tract transfers its characteristics onto the sounds produced at the glottis, depending on its tridimensional configuration.Aimthis 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 methodthis 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.Resultsstatistical 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.Conclusionin 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.

Highlights

The geometry of the vocal tract in adults is similar to a straight tube sealed on one of its ends; it averages 17 cm in length and its three first peaks of resonance range at about 500, 1500 and 2500Hz1-3 respectively
The vocal tract transfers its characteristics to the sounds produced at the glottis in accordance with its tridimensional configuration, which results from the positioning of its component structures
Formants vary depending on the tridimensional arrangement of the vocal tract; the first three formants are fundamental for vowel acoustic identity

Summary

Introduction

The vocal tract transfers its characteristics to the sounds produced at the glottis in accordance with its tridimensional configuration, which results from the positioning of its component structures. Such transfer, referred to as transfer factor, changes the intensity of harmonics, as a consequence of the resonance phenomenon. Formants vary depending on the tridimensional arrangement of the vocal tract; the first three formants are fundamental for vowel acoustic identity. Standardized speech evaluation protocols preferentially use vowels /a/, /i/, /u/ as they are acoustically very different from each other, favoring the observation of possible disturbances in the various parts of the spectrum against the corresponding configurations of the vocal tract

Objectives

Methods

Conclusion