Individual Difference And Acoustic Effect Of Female Laryngeal Cavities

The research purpose of our study is examine the role of the female laryngeal cavity in generating individual acoustic characteristics of vowel sounds.The laryngeal cavity is a lower part of the vocal tract above the glottis.It include laryngeal vestibule and laryngeal ventricle.MRI data of vowel /a/ and vowel /i/ for 3 female subjects and 1 male subjects are obtained to analyze the acoustic effect of female laryngeal cavity.The MRI data were re-sampled to have 1-mm thickness in axial plane and then the boundaries of the vocal tract were manually traced.The traced images were interpolated to have 0.5-mm slice thickness and converted into a 3D vocal-tract model by Mimics.The teeth were superimposed to the vocal-tract models in 3D space.3D vocal-tract models were processed to have an outward wall of 3-mm thickness and printed as solid vocal-tract models by a 3D printer.The research contents of this study include three parts.First,the accurate of the models were estimated by the area function and transmission line model.Then,the individual variation of male and female laryngeal cavity were confirmed by the morphological analysis of laryngeal cavity area functions.The result shows that female laryngeal cavity has relatively stable cross area and shape comparing with those for the male subject.Last,acoustic experiments on the laryngeal cavity were conducted by the solid vocal-tract models with different glottis conditions simulated by different hole size of glottal couplers.We use 1.2-mm hole to simulate the closed glottis,and 2.0-mm,3.0-mm and 4.0-mm holes to simulate the open glottis.The results indicate that the female laryngeal cavity denotes a wider frequency change at about 3-4.5 kHz of vowels /a/ and /i/ in comparison of data between open and closed glottis conditions.