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  • 1.
    Arnela, Marc
    et al.
    GTM–Grup de recerca en Tecnologies Mèdia, La Salle, Universitat Ramon Llull, C/Quatre Camins 30, Barcelona, E-08022, Catalonia, Spain.
    Blandin, Rémi
    GIPSA-Lab, Unité Mixte de Recherche au Centre National de la Recherche Scientifique 5216, Grenoble Campus, St. Martin d'Heres, F-38402, France.
    Dabbaghchian, Saeed
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    Guasch, Oriol
    GTM–Grup de recerca en Tecnologies Mèdia, La Salle, Universitat Ramon Llull, C/Quatre Camins 30, Barcelona, E-08022, Catalonia, Spain.
    Alías, Francesc
    GTM–Grup de recerca en Tecnologies Mèdia, La Salle, Universitat Ramon Llull, C/Quatre Camins 30, Barcelona, E-08022, Catalonia, Spain.
    Pelorson, Xavier
    GIPSA-Lab, Unité Mixte de Recherche au Centre National de la Recherche Scientifique 5216, Grenoble Campus, St. Martin d'Heres, F-38402, France.
    Van Hirtum, Annemie
    GIPSA-Lab, Unité Mixte de Recherche au Centre National de la Recherche Scientifique 5216, Grenoble Campus, St. Martin d'Heres, F-38402, France.
    Engwall, Olov
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    Influence of lips on the production of vowels based on finite element simulations and experiments2016In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 139, no 5, p. 2852-2859Article in journal (Refereed)
    Abstract [en]

    Three-dimensional (3-D) numerical approaches for voice production are currently being investigated and developed. Radiation losses produced when sound waves emanate from the mouth aperture are one of the key aspects to be modeled. When doing so, the lips are usually removed from the vocal tract geometry in order to impose a radiation impedance on a closed cross-section, which speeds up the numerical simulations compared to free-field radiation solutions. However, lips may play a significant role. In this work, the lips' effects on vowel sounds are investigated by using 3-D vocal tract geometries generated from magnetic resonance imaging. To this aim, two configurations for the vocal tract exit are considered: with lips and without lips. The acoustic behavior of each is analyzed and compared by means of time-domain finite element simulations that allow free-field wave propagation and experiments performed using 3-D-printed mechanical replicas. The results show that the lips should be included in order to correctly model vocal tract acoustics not only at high frequencies, as commonly accepted, but also in the low frequency range below 4 kHz, where plane wave propagation occurs.

  • 2. Arnela, Marc
    et al.
    Dabbaghchian, Saeed
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Blandin, Rémi
    Guasch, Oriol
    Engwall, Olov
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Hirtum, Annemie Van
    Pelorson, Xavier
    Influence of vocal tract geometry simplifications on the numerical simulation of vowel sounds2016In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 140, no 3, p. 1707-1718Article in journal (Refereed)
    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.

  • 3. Arnela, Marc
    et al.
    Dabbaghchian, Saeed
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    Blandin, Rémi
    Guasch, Oriol
    Engwall, Olov
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    Pelorson, Xavier
    Van Hirtum, Annemie
    Effects of vocal tract geometry simplifications on the numerical simulation of vowels2015In: PAN EUROPEAN VOICE CONFERENCE ABSTRACT BOOK: Proceedings e report 104, Firenze University Press, 2015, p. 177-Conference paper (Other academic)
  • 4.
    Arnela, Marc
    et al.
    GTM Grup de recerca en Tecnologies Mèdia, La Salle, Universitat Ramon Llull, Barcelona, Spain.
    Dabbaghchian, Saeed
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Guasch, Oriol
    GTM Grup de recerca en Tecnologies Mèdia, La Salle, Universitat Ramon Llull, Barcelona, Spain.
    Engwall, Olov
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    A semi-polar grid strategy for the three-dimensional finite element simulation of vowel-vowel sequences2017In: Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH 2017, The International Speech Communication Association (ISCA), 2017, Vol. 2017, p. 3477-3481Conference paper (Refereed)
    Abstract [en]

    Three-dimensional computational acoustic models need very detailed 3D vocal tract geometries to generate high quality sounds. Static geometries can be obtained from Magnetic Resonance Imaging (MRI), but it is not currently possible to capture dynamic MRI-based geometries with sufficient spatial and time resolution. One possible solution consists in interpolating between static geometries, but this is a complex task. We instead propose herein to use a semi-polar grid to extract 2D cross-sections from the static 3D geometries, and then interpolate them to obtain the vocal tract dynamics. Other approaches such as the adaptive grid have also been explored. In this method, cross-sections are defined perpendicular to the vocal tract midline, as typically done in 1D to obtain the vocal tract area functions. However, intersections between adjacent cross-sections may occur during the interpolation process, especially when the vocal tract midline quickly changes its orientation. In contrast, the semi-polar grid prevents these intersections because the plane orientations are fixed over time. Finite element simulations of static vowels are first conducted, showing that 3D acoustic wave propagation is not significantly altered when the semi-polar grid is used instead of the adaptive grid. The vowel-vowel sequence [ɑi] is finally simulated to demonstrate the method.

  • 5. Arnela, Marc
    et al.
    Guasch, Oriol
    Dabbaghchian, Saeed
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    Engwall, Olov
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    FINITE ELEMENT GENERATION OF VOWEL SOUNDS USING DYNAMIC COMPLEX THREE-DIMENSIONAL VOCAL TRACTS2016In: PROCEEDINGS OF THE 23RD INTERNATIONAL CONGRESS ON SOUND AND VIBRATION: FROM ANCIENT TO MODERN ACOUSTICS, INT INST ACOUSTICS & VIBRATION , 2016Conference paper (Refereed)
    Abstract [en]

    Three-dimensional (3D) numerical simulations of the vocal tract acoustics require very detailed vocal tract geometries in order to generate good quality vowel sounds. These geometries are typically obtained from Magnetic Resonance Imaging (MRI), from which a volumetric representation of the complex vocal tract shape is obtained. Static vowel sounds can then be generated using a finite element code, which simulates the propagation of acoustic waves through the vocal tract when a given train of glottal pulses is introduced at the glottal cross-section. A more challenging problem to solve is that of generating dynamic vowel sounds. On the one hand, the acoustic wave equation has to be solved in a computational domain with moving boundaries, which entails some numerical difficulties. On the other hand, the finite element meshes where acoustic wave propagation is computed have to move according to the dynamics of these very complex vocal tract shapes. In this work this problem is addressed. First, the acoustic wave equation in mixed form is expressed in an Arbitrary Lagrangian-Eulerian (ALE) framework to account for the vocal tract wall motion. This equation is numerically solved using a stabilized finite element approach. Second, the dynamic 3D vocal tract geometry is approximated by a finite set of cross-sections with complex shape. The time-evolution of these cross-sections is used to move the boundary nodes of the finite element meshes, while inner nodes are computed through diffusion. Some dynamic vowel sounds are presented as numerical examples.

  • 6.
    Dabbaghchian, Saeed
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH.
    Computational Modeling of the Vocal Tract: Applications to Speech Production2018Doctoral 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.

  • 7.
    Dabbaghchian, Saeed
    et al.
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    Arnela, Marc
    Engwall, Olov
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    SIMPLIFICATION OF VOCAL TRACT SHAPES WITH DIFFERENT LEVELS OF DETAIL2015In: Proceedings of the 18th International Congress of Phonetic Sciences. Glasgow, UK, University of Glasgow , 2015, p. 1-5Conference paper (Refereed)
    Abstract [en]

    We propose a semi-automatic method to regenerate simplified vocal tract geometries from very detailed input (e.g. MRI-based geometry) with the possibility to control the level of detail, while maintaining the overall properties. The simplification procedure controls the number and organization of the vertices in the vocal tract surface mesh and can be assigned to replace complex cross-sections with regular shapes. Six different geometry regenerations are suggested: bent or straight vocal tract centreline, combined with three different types of cross-sections; namely realistic, elliptical or circular. The key feature in the simplification is that the cross-sectional areas and the length of the vocal tract are maintained. This method may, for example, be used to facilitate 3D finite element method simulations of vowels and diphthongs and to examine the basic acoustic characteristics of vocal tract in printed physical replicas. Furthermore, it allows for multimodal solutions of the wave equation.

  • 8.
    Dabbaghchian, Saeed
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH.
    Arnela, Marc
    GTM Grup de recerca en Tecnologies Mèdia, La Salle, Universitat Ramon Llull, Barcelona, Spain.
    Engwall, Olov
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH.
    Guasch, Oriol
    GTM Grup de recerca en Tecnologies Mèdia, La Salle, Universitat Ramon Llull, Barcelona, Spain.
    Reconstruction of vocal tract geometries from biomechanical simulations2018In: International Journal for Numerical Methods in Biomedical Engineering, ISSN 2040-7939, E-ISSN 2040-7947Article in journal (Refereed)
    Abstract [en]

    Medical imaging techniques are usually utilized to acquire the vocal tract geometry in 3D, which may then be used, eg, for acoustic/fluid simulation. As an alternative, such a geometry may also be acquired from a biomechanical simulation, which allows to alter the anatomy and/or articulation to study a variety of configurations. In a biomechanical model, each physical structure is described by its geometry and its properties (such as mass, stiffness, and muscles). In such a model, the vocal tract itself does not have an explicit representation, since it is a cavity rather than a physical structure. Instead, its geometry is defined implicitly by all the structures surrounding the cavity, and such an implicit representation may not be suitable for visualization or for acoustic/fluid simulation. In this work, we propose a method to reconstruct the vocal tract geometry at each time step during the biomechanical simulation. Complexity of the problem, which arises from model alignment artifacts, is addressed by the proposed method. In addition to the main cavity, other small cavities, including the piriform fossa, the sublingual cavity, and the interdental space, can be reconstructed. These cavities may appear or disappear by the position of the larynx, the mandible, and the tongue. To illustrate our method, various static and temporal geometries of the vocal tract are reconstructed and visualized. As a proof of concept, the reconstructed geometries of three cardinal vowels are further used in an acoustic simulation, and the corresponding transfer functions are derived.

  • 9.
    Dabbaghchian, Saeed
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH.
    Arnela, Marc
    Engwall, Olov
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH.
    Guasch, Oriol
    Synthesis of vowels and vowel-vowel utterancesusing a 3D biomechanical-acoustic model2018In: IEEE/ACM Transactions on Audio, Speech, and Language Processing, ISSN 2329-9290Article in journal (Refereed)
    Abstract [en]

    A link is established between a 3D biomechanicaland acoustic model allowing for the umerical synthesis of vowelsounds by contraction of the relevant muscles. That is, thecontraction of muscles in the biomechanical model displacesand deforms the articulators, which in turn deform the vocaltract shape. The mixed wave equation for the acoustic pressureand particle velocity is formulated in an arbitrary Lagrangian-Eulerian framework to account for moving boundaries. Theequations are solved numerically using the finite element method.Since the activation of muscles are not fully known for a givenvowel sound, an inverse method is employed to calculate aplausible activation pattern. For vowel-vowel utterances, two different approaches are utilized: linear interpolation in eithermuscle activation or geometrical space. Although the former isthe natural choice for biomechanical modeling, the latter is usedto investigate the contribution of biomechanical modeling onspeech acoustics. Six vowels [ɑ, ə, ɛ, e, i, ɯ] and three vowel-vowelutterances [ɑi, ɑɯ, ɯi] are synthesized using the 3D model. Results,including articulation, formants, and spectrogram of vowelvowelsounds, are in agreement with previous studies.Comparingthe spectrogram of interpolation in muscle and geometrical spacereveals differences in all frequencies, with the most extendeddifference in the second formant transition.

  • 10.
    Dabbaghchian, Saeed
    et al.
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    Arnela, Marc
    Engwall, Olov
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    Guasch, Oriol
    Synthesis of VV utterances from muscle activation to sound with a 3d model2017In: Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH 2017, The International Speech Communication Association (ISCA), 2017, p. 3497-3501Conference paper (Refereed)
    Abstract [en]

    We propose a method to automatically generate deformable 3D vocal tract geometries from the surrounding structures in a biomechanical model. This allows us to couple 3D biomechanics and acoustics simulations. The basis of the simulations is muscle activation trajectories in the biomechanical model, which move the articulators to the desired articulatory positions. The muscle activation trajectories for a vowel-vowel utterance are here defined through interpolation between the determined activations of the start and end vowel. The resulting articulatory trajectories of flesh points on the tongue surface and jaw are similar to corresponding trajectories measured using Electromagnetic Articulography, hence corroborating the validity of interpolating muscle activation. At each time step in the articulatory transition, a 3D vocal tract tube is created through a cavity extraction method based on first slicing the geometry of the articulators with a semi-polar grid to extract the vocal tract contour in each plane and then reconstructing the vocal tract through a smoothed 3D mesh-generation using the extracted contours. A finite element method applied to these changing 3D geometries simulates the acoustic wave propagation. We present the resulting acoustic pressure changes on the vocal tract boundary and the formant transitions for the utterance [Ai].

  • 11.
    Dabbaghchian, Saeed
    et al.
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Arnela, Marc
    GTM Grup de recerca en Tecnologies Mèdia, La Salle, Universitat Ramon Llull, Barcelona, Spain.
    Engwall, Olov
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Guasch, Oriol
    GTM Grup de recerca en Tecnologies Mèdia, La Salle, Universitat Ramon Llull, Barcelona, Spain.
    Stavness, Ian
    Badin, Pierre
    Using a Biomechanical Model and Articulatory Data for the Numerical Production of Vowels2016In: Interspeech 2016, 2016, p. 3569-3573Conference paper (Refereed)
    Abstract [en]

    We introduce a framework to study speech production using a biomechanical model of the human vocal tract, ArtiSynth. Electromagnetic articulography data was used as input to an inverse tracking simulation that estimates muscle activations to generate 3D jaw and tongue postures corresponding to the target articulator positions. For acoustic simulations, the vocal tract geometry is needed, but since the vocal tract is a cavity rather than a physical object, its geometry does not explicitly exist in a biomechanical model. A fully-automatic method to extract the 3D geometry (surface mesh) of the vocal tract by blending geometries of the relevant articulators has therefore been developed. This automatic extraction procedure is essential, since a method with manual intervention is not feasible for large numbers of simulations or for generation of dynamic sounds, such as diphthongs. We then simulated the vocal tract acoustics by using the Finite Element Method (FEM). This requires a high quality vocal tract mesh without irregular geometry or self-intersections. We demonstrate that the framework is applicable to acoustic FEM simulations of a wide range of vocal tract deformations. In particular we present results for cardinal vowel production, with muscle activations, vocal tract geometry, and acoustic simulations.

  • 12.
    Dabbaghchian, Saeed
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH.
    Nilsson, Isak
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH.
    Engwall, Olov
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH.
    From Tongue Movement Data to Muscle Activation – A Preliminary Study of Artisynth's Inverse Modelling2014Conference paper (Other academic)
    Abstract [en]

    Finding the muscle activations during speech production is an important part of developing a comprehensive biomechanical model of speech production. Although there are some direct ways, like Electromyography, for measuring muscle activations, these methods usually are highly invasive and sometimes not reliable. They are more over impossible to use for all muscles. In this study we therefore explore an indirect way to estimate tongue muscle activations during speech production by combining Electromagnetic Articulography (EMA) measurements of tongue movements and the inverse modeling in Artisynth. With EMA we measure the time-changing 3D positions of four sensors attached to the tongue surface for a Swedish female subject producing vowel-vowel and vowelconsonant-vowel (VCV) sequences. The measured sensor positions are used as target points for corresponding virtual sensors introduced in the tongue model of Artisynth’s inverse modelling framework, which computes one possible combination of muscle activations that results in the observed sequence of tongue articulations. We present resynthesized tongue movements in the Artisynth model and verify the results by comparing the calculated muscle activations with literature.

  • 13.
    Meena, Raveesh
    et al.
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    Dabbaghchian, Saeed
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    Stefanov, Kalin
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
    A Data-driven Approach to Detection of Interruptions in Human-–human Conversations2014Conference paper (Refereed)
1 - 13 of 13
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