Yosuke Tanabe

Low-dimensional models of the glottal flow incorporating viscous-inviscid interaction.

The behavior of glottal flow can, to a large extent, be characterized by development and separation of the boundary layer. The point of flow separation is known to vary during the phonatory cycle due to change in channel configuration. To take the movable nature of the separation point into account, the boundary-layer equation is solved numerically, and the values of the characteristic quantities are determined as well as the point of separation. Development of the boundary layer in general reduces the effective size of the channel, and, therefore, increases the core flow velocity, which, in turn provides the boundary condition of the boundary-layer equation. The interaction between the viscous (boundary layer) and inviscid (core flow) parts of the glottal flow is, therefore, strongly indicated. To apply this viscous-inviscid interaction, the expression of the core flow is derived for a two-dimensional flow field, and is solved jointly with the boundary-layer equation. Numerical results are shown to examine the effect of the Reynolds number and glottal configuration, with special emphasis on the comparison of flow models developed for one- and two-dimensional flow fields. Numerical results are also quantitatively compared with data obtained from flow measurement experiments.

Development of Particle Velocity Transfer Path Analysis

The transfer path analysis (TPA) in terms of sound pressure has been implemented for decades in many application areas, such as car, train and construction machine. In this article, we propose a transfer path analysis where particle velocity is employed as the measure of TPA. Sound pressure is a scalar quantity, while particle velocity, which is the other fundamental quantity of sound, is a vector quantity. The phase differences among particle velocity vector components have to be generally considered. For TPA, not only the six degrees-of-freedom of each path motion, but also the three degrees-of-freedom of the particle velocity at the receiver location have to be considered together for an effective path rank ordering. We first propose the formulation of the particle velocity transfer path analysis where the same formulation of the standard sound pressure transfer path analysis is assumed to hold true for each direction of particle velocity. In order to verify the proposed particle velocity transfer path analysis, we carry out an experiment using a simple test box structure. As a result we have found that the error in the particle velocity vector synthesis is acceptably small, and is as small as the error in the standard sound pressure synthesis, which indicates that the same synthesis method can be employed. We then perform rank ordering of the particle velocity transmission paths. Here, a simple method of path rank ordering is applied. Lastly, we briefly discuss sound energy as a measure of TPA.Copyright

Formulation of total complex power and energy flows into a discrete system.

By considering total inputs into a discrete system, this letter analytically formulates and summarizes the relationships in the complex-form power and energy flows and the dissipated power and Lagrangian energy of the system. The matrix inverse method to obtain the force/moment necessary for the power/energy flow is shown as an indirect yet analytically exact method. A 2 degree-of-freedom system is employed to analytically validate the derived formulas, followed by a computational confirmation. A finite element plate-beam model is further utilized to computationally confirm the relationships in the complex power and energy flows.

Changes in the vocal tract shape of sopranos at high pitch

As sopranos increase their fundamental frequency (F0) to sing at higher pitches, they also increase the first resonance frequency (R1) of their vocal tract. This is probably to avoid sudden F0 changes when F0 and R1 cross. It is unclear, however, how sopranos change vocal tract shape to increase R1. Therefore, the vocal tract shapes of two Japanese sopranos during production of the sung vowel /a/ in the modal register (A4 and D5) and in the falsetto register (G5) were measured by MRI. The measured vocal tract shapes were compared with each other and their area functions were extracted to calculate acoustic characteristics. Results showed that changes in the vocal tract shape were small between A4 and D5, while changes were large between D5 and G5. At G5, it was observed in both subjects that the lower jaw opened, the pharyngeal wall and tongue root advanced, and the larynx retracted. In addition, one subject shortened the laryngeal cavity length. All these changes achieved R1 increase, in agreement with t...

Study on the exactness of alternative indirect force estimation methods, power dissipation calculation by power or energy flow, and transfer path analysis for structure-borne sound

In our presentation, it is first clarified that the matrix inverse method which gives interfacial forces using X/F-type frequency response functions among parallel interfacial points is an exact method derived from Newton’s equation of motion. The alternative method using F/X-type frequency response functions with blocked boundaries is next explained as another exact method, though implementation of the blocked boundary may be difficult for real-life systems. Next, as an application of interfacial force, it is shown that the real part of power flow and the imaginary part of energy flow correspond to mechanical power dissipation. When all the power or energy flows into a system are counted, it gives the exact power dissipation of the system. As another application, the exactness of transfer path analysis for structure-borne sound is examined with brief discussion of velocity potential. Computational demonstrations and validations are given for the derived formulas, using a simple finite element model. All ...

Study on Driving Point Power Flow as Power Dissipation in Discrete Vibratory Systems

Mechanical power flow into a discrete system is formulated as power dissipation in the system using driving point advantages. Firstly, the complex-valued power flow into a system is defined, and it is shown that the real part (or active power) corresponds to the power dissipation, and the imaginary part (or reactive power) contains the Lagrangian energy. To represent the power dissipation in the system, all the power flows into the system must be counted. Otherwise, the value of power flow may become negative, and its physical interpretation may be troublesome. One of the main advantages of the formulated power flow is that to estimate the power dissipation in the system, only the power flows into the system are necessary. In other words, only the driving point power flows into the system are needed, and no information inside the system is required. Next, to estimate interfacial force/moment for the power flow into a sub-system, the two alternative indirect methods are presented. It is shown that these are exact methods utilizing the responses and the frequency response functions at the driving points only. This is another remarkable characteristic of the driving point. A 7 degree-of-freedom system is employed as an example case, and the presented formulations are confirmed computationally.Copyright

Simulation of the coupling between vocal-fold vibration and time-varying vocal tract

Acoustic coupling between the voiced sound source and the time-varying acoustic load during phonation was simulated by combining the vocal-fold model of [S. Adachi etal., J. Acoust. Soc. Am 117(5) (2005)] with the vocal-tract model of [P. Mokhtari etal., Speech Commun. 50, 179–190 (2008)]. The combined simulation model enables to analyze the dynamic behavior of the vocal folds due to the time-varying shape of the vocal tract. An example of vocal-fold behavior is shown for sustained phonation of the Japanese vowel sequence “aiueo.” [This research was partly supported by Kakenhi (Grant Nos. 21500184, 21300071).]