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Influence of vocal tract geometry simplifications on the numerical simulation of vowel sounds
KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.ORCID iD: 0000-0002-8991-1016
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2016 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 140, no 3, p. 1707-1718Article in journal (Refereed) Published
Abstract [en]

For many years, the vocal tract shape has been approximated by one-dimensional (1D) area functions to study the production of voice. More recently, 3D approaches allow one to deal with the complex 3D vocal tract, although area-based 3D geometries of circular cross-section are still in use. However, little is known about the influence of performing such a simplification, and some alternatives may exist between these two extreme options. To this aim, several vocal tract geometry simplifications for vowels [ɑ], [i], and [u] are investigated in this work. Six cases are considered, consisting of realistic, elliptical, and circular cross-sections interpolated through a bent or straight midline. For frequencies below 4–5 kHz, the influence of bending and cross-sectional shape has been found weak, while above these values simplified bent vocal tracts with realistic cross-sections are necessary to correctly emulate higher-order mode propagation. To perform this study, the finite element method (FEM) has been used. FEM results have also been compared to a 3D multimodal method and to a classical 1D frequency domain model.

Place, publisher, year, edition, pages
Acoustical Society of America (ASA), 2016. Vol. 140, no 3, p. 1707-1718
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-192600DOI: 10.1121/1.4962488ISI: 000386932500032Scopus ID: 2-s2.0-84988353352OAI: oai:DiVA.org:kth-192600DiVA, id: diva2:971286
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EUNISON
Note

QC 20161010

Available from: 2016-09-15 Created: 2016-09-15 Last updated: 2018-11-16Bibliographically approved
In thesis
1. Computational Modeling of the Vocal Tract: Applications to Speech Production
Open this publication in new window or tab >>Computational Modeling of the Vocal Tract: Applications to Speech Production
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Human speech production is a complex process, involving neuromuscular control signals, the effects of articulators' biomechanical properties and acoustic wave propagation in a vocal tract tube of intricate shape. Modeling these phenomena may play an important role in advancing our understanding of the involved mechanisms, and may also have future medical applications, e.g., guiding doctors in diagnosing, treatment planning, and surgery prediction of related disorders, ranging from oral cancer, cleft palate, obstructive sleep apnea, dysphagia, etc.

A more complete understanding requires models that are as truthful representations as possible of the phenomena. Due to the complexity of such modeling, simplifications have nevertheless been used extensively in speech production research: phonetic descriptors (such as the position and degree of the most constricted part of the vocal tract) are used as control signals, the articulators are represented as two-dimensional geometrical models, the vocal tract is considered as a smooth tube and plane wave propagation is assumed, etc.

This thesis aims at firstly investigating the consequences of such simplifications, and secondly at contributing to establishing unified modeling of the speech production process, by connecting three-dimensional biomechanical modeling of the upper airway with three-dimensional acoustic simulations. The investigation on simplifying assumptions demonstrated the influence of vocal tract geometry features — such as shape representation, bending and lip shape — on its acoustic characteristics, and that the type of modeling — geometrical or biomechanical — affects the spatial trajectories of the articulators, as well as the transition of formant frequencies in the spectrogram.

The unification of biomechanical and acoustic modeling in three-dimensions allows to realistically control the acoustic output of dynamic sounds, such as vowel-vowel utterances, by contraction of relevant muscles. This moves and shapes the speech articulators that in turn dene the vocal tract tube in which the wave propagation occurs. The main contribution of the thesis in this line of work is a novel and complex method that automatically reconstructs the shape of the vocal tract from the biomechanical model. This step is essential to link biomechanical and acoustic simulations, since the vocal tract, which anatomically is a cavity enclosed by different structures, is only implicitly defined in a biomechanical model constituted of several distinct articulators.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2018. p. 105
Series
TRITA-EECS-AVL ; 2018:90
Keywords
vocal tract, upper airway, speech production, biomechanical model, acoustic model, vocal tract reconstruction
National Category
Computer Sciences
Research subject
Speech and Music Communication
Identifiers
urn:nbn:se:kth:diva-239071 (URN)978-91-7873-021-6 (ISBN)
Public defence
2018-12-07, D2, Lindstedtsvägen 5, Stockholm, 14:00 (English)
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Note

QC 20181116

Available from: 2018-11-16 Created: 2018-11-16 Last updated: 2018-11-16Bibliographically approved

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