scholarly journals Numerical investigation of effects of incisor angle on production of sibilant /s/

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
HsuehJui Lu ◽  
Tsukasa Yoshinaga ◽  
ChungGang Li ◽  
Kazunori Nozaki ◽  
Akiyoshi Iida ◽  
...  
Keyword(s):  
Vocal Tract ◽  
Frequency Range ◽  
Flow Solver ◽  
Time Stepping ◽  
Dental Prostheses ◽  
The Hierarchical Structure ◽  
High Turbulence ◽  
The Fourier Transform ◽  
Intensity Region ◽  
Field Sound

AbstractThe effects of the inclination angle of the incisor on the speech production of the fricative consonant /s/ was investigated using an implicit compressible flow solver. The hierarchical structure grid was applied to reduce the grid generation time for the vocal tract geometry. The airflow and sound during the pronunciation of /s/ were simulated using the adaptively switched time stepping scheme, and the angle of the incisor in the vocal tract was changed from normal position up to 30°. The results showed that increasing the incisor angle affected the flow configuration and moved the location of the high turbulence intensity region thereby decreased the amplitudes of the sound in the frequency range from 8 to 12 kHz. Performing the Fourier transform on the velocity fluctuation, we found that the position of large magnitudes of the velocity at 10 kHz shifted toward the lip outlet when the incisor angle was increased. In addition, separate acoustic simulations showed that the shift in the potential sound source position decreased the far-field sound amplitudes above 8 kHz. These results provide the underlying insights necessary to design dental prostheses for the production of sibilant fricatives.

scholarly journals Estimation of S-parameters and dielectric permittivity of quartz ceramics samples in millimeter waveband

Doklady BGUIR ◽  
2021 ◽  
Vol 19 (7) ◽  
pp. 65-71
Author(s):  
N. A. Pevneva ◽  
D. A. Kondrashov ◽  
A. L. Gurskii ◽  
A. V. Gusinsky
Keyword(s):  
Dielectric Constant ◽  
Dielectric Permittivity ◽  
Ceramic Materials ◽  
Reflection And Transmission Coefficients ◽  
Frequency Range ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Higher Order Modes ◽  
S Parameters ◽  
The Fourier Transform

A modified Nicholson – Ross – Weir method was used to determine complex parameters and dielectric permittivity of ceramic materials in the range 78.33–118.1 GHz. The measuring equipment is a meter of complex reflection and transmission coefficients, a waveguide measuring canal with a special measuring cell, consisting of two irregular waveguides and a waveguide chamber between them, which provides insignificant influence of higher-order modes. The dependences of the amplitude and phase of the reflection and transmission coefficients on frequency were obtained experimentally for fluoroplastic and three ceramic samples in the frequency range 78.33–118.1 GHz. The obtained S-parameters are processed according to an algorithm that includes their averaging based on the Fourier transform in order to obtain the values of the dielectric permittivity. Fluoroplastic was used as a reference material with a known dielectric constant. The dielectric constant of fluoroplastic has a stable value of 2.1 in the above mentioned frequency range. The dielectric constant of sample No. 1 varies from 3.6 to 2.5 at the boundaries of the range, sample No. 2 – from 3.7 to 2.1, sample No. 3 – from 2.9 to 1.5. The experimental data are in satisfactory agreement with the literature data for other frequencies taking into account the limits set by the measurement uncertainty.

Numerical Solution of Incompressible Unsteady Flows in Turbomachinery

2000 ◽  
Vol 123 (3) ◽  
pp. 680-685 ◽  
Author(s):  
L. He ◽  
K. Sato
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Unsteady Flows ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Flow Solver ◽  
Time Stepping ◽  
Incompressible Viscous Flow ◽  
Dual Time Stepping

A three-dimensional incompressible viscous flow solver of the thin-layer Navier-Stokes equations was developed for the unsteady turbomachinery flow computations. The solution algorithm for the unsteady flows combines the dual time stepping technique with the artificial compressibility approach for solving the incompressible unsteady flow governing equations. For time accurate calculations, subiterations are introduced by marching the equations in the pseudo-time to fully recover the incompressible continuity equation at each real time step, accelerated with a multi-grid technique. Computations of test cases show satisfactory agreements with corresponding theoretical and experimental results, demonstrating the validity and applicability of the present method to unsteady incompressible turbomachinery flows.

scholarly journals Overtone focusing in biphonic tuvan throat singing

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Christopher Bergevin ◽  
Chandan Narayan ◽  
Joy Williams ◽  
Natasha Mhatre ◽  
Jennifer KE Steeves ◽  
...  
Keyword(s):  
Sound Production ◽  
Vocal Tract ◽  
Low Frequency ◽  
Resonance Imaging ◽  
Frequency Range ◽  
Vocal Cords ◽  
Singing Style ◽  
Narrow Frequency Range ◽  
The Republic ◽  
Throat Singing

Khoomei is a unique singing style originating from the republic of Tuva in central Asia. Singers produce two pitches simultaneously: a booming low-frequency rumble alongside a hovering high-pitched whistle-like tone. The biomechanics of this biphonation are not well-understood. Here, we use sound analysis, dynamic magnetic resonance imaging, and vocal tract modeling to demonstrate how biphonation is achieved by modulating vocal tract morphology. Tuvan singers show remarkable control in shaping their vocal tract to narrowly focus the harmonics (or overtones) emanating from their vocal cords. The biphonic sound is a combination of the fundamental pitch and a focused filter state, which is at the higher pitch (1–2 kHz) and formed by merging two formants, thereby greatly enhancing sound-production in a very narrow frequency range. Most importantly, we demonstrate that this biphonation is a phenomenon arising from linear filtering rather than from a nonlinear source.

scholarly journals Extracting Features of Transient Electric Fields With Fourier And Wavelet Transform–A Case Study Of Lightning Positive Return Stroke

2021 ◽  
Vol 14 (14) ◽  
pp. 44-50
Author(s):  
Shriram Sharma
Keyword(s):  
Fourier Transform ◽  
Wavelet Transform ◽  
Spectral Density ◽  
Frequency Spectrum ◽  
Electric Fields ◽  
Frequency Range ◽  
Return Stroke ◽  
The Fourier Transform ◽  
Positive Return ◽  
Domain Information

Frequency domain information were extracted from the time domain electric fields pertinent to the lightning positive return strokes applying Fourier transform and Wavelet transform. The electric field radiated by positive ground flashes striking the sea were recorded at 10 ns resolution at a coastal station to minimize the propagation effects. The frequency spectrum of the electric field of positive return strokes were computed applying the Fourier transform technique in the range of 10 kHz to 20 MHz owing to the fact that this range of frequency is of very much interest to the researchers and design engineers. The amplitude of the energy spectral density decreases nearly as ƒ-1 from 10 kHz to about 0.1 MHz and drops nearly as ƒ-2 up to 8 MHz.  Applying the wavelet transform technique, the same positive return strokes are found to radiate in the frequency range of 5.5 to 81 kHz with the average spread distribution of 13.6 kHz to about 30 kHz. From frequency spectrum obtained from the Fourier transform it is difficult to identify as which phase of the return stroke radiates in the higher frequency range and that in the lower frequency range, whereas, one can easily identify from the frequency spectrum obtained with the wavelet transform that ramp portion of the positive return stroke radiates in the larger spectral range as compared to that of initial peak of the return stroke.  Also, from the spectral density map obtained from wavelet transform one can easily observe the contribution of each phase in a range of frequency, which is not possible from the Fourier transform technique. Clearly, the wavelet transform is much more powerful tool to extract the frequency domain information of a non-stationary signal as compared to that of Fourier transform.

scholarly journals Magnetic storm free ULF analysis in relation with earthquakes in Taiwan

2012 ◽  
Vol 12 (5) ◽  
pp. 1747-1754 ◽  
Author(s):  
S. Wen ◽  
C.-H. Chen ◽  
H.-Y. Yen ◽  
T.-K. Yeh ◽  
J.-Y. Liu ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Cross Correlation ◽  
Low Frequency ◽  
Magnetic Anomalies ◽  
Magnetic Storms ◽  
Frequency Range ◽  
Geomagnetic Data ◽  
Before And After ◽  
The Cross ◽  
The Fourier Transform

Abstract. Despite early optimism, pre-earthquake anomalous phenomena can be determined by using enhanced amplitude at the ultra-low-frequency range from geomagnetic data via the Fourier transform. In reality, accuracy of the enhanced amplitude in relation to earthquakes (deduced from time-varied geomagnetic data) would be damaged by magnetic storms and/or other unwanted influences resulting from solar activity and/or variations in the ionosphere, respectively. We substitute values of the cross correlation between amplitudes, summarized from the earthquake-related (0.1–0.01 Hz) and the comparable (0.01–0.001 Hz) frequency bands, for isolated amplitude enhancements as indexes of determination associated with seismo-magnetic anomalies to mitigate disturbance caused by magnetic storms. A station located about 300 km away from the others is also taken into account to further examine whether changes of the cross correlation values are caused by seismo-magnetic anomalies limited within local regions or not. Analytical results show that the values suddenly decrease near epicenters a few days before and after 67% (= 6/9) of earthquakes (M > = 5) in Taiwan between September 2010 and March 2011. Seismo-magnetic signals determined by using the values of cross correlation methods partially improve results yielded from the Fourier transform alone and provide advantageous information of earthquake locations.

scholarly journals Variation of Formant Frequency with Nepalese Vowels

2020 ◽  
pp. 16-21
Author(s):  
S.K. Adhikari
Keyword(s):  
Vocal Tract ◽  
Free Field ◽  
Predictive Coding ◽  
Initial Position ◽  
Frequency Range ◽  
Linear Predictive Coding ◽  
Formant Frequency ◽  
Formant Frequencies ◽  
Speech Spectrum ◽  
Shape And Size

The regions of speech spectrum in which the frequency corresponds to relatively large amplitude are known as formants. For any vocalic sounds, number of formants may occur in the frequency range 0 to 4000 Hz. The formant frequencies of speech sounds are directly depending up on the shape and size of vocal tract. The aim of study was to study the variation of formant frequency with Nepalese vowels. Ten Nepalese vowels word in initial position /VC/ as spoken three times by 10 male and 10 female Nepali speakers were recorded in system in the free field of partially acoustically treated room. PRRAT software is used to digitize and analyze the data. Linear predictive coding (LPC) spectra were obtained for each of vowels and formant frequencies were measured. By plotting curve between formant frequencies and vowels, explain their variation.  

Numerical Simulation of Underwater Propulsor Using an Unstructured Overset Mesh Technique

2011 ◽  
Author(s):  
Sang Jun An ◽  
Oh Joon Kwon
Keyword(s):  
Time Integration ◽  
Equation Model ◽  
Hydrodynamic Characteristics ◽  
Flow Solver ◽  
Time Stepping ◽  
Dual Time Stepping ◽  
Underwater Propulsor ◽  
Volume Method ◽  
Thrust And Torque ◽  
Mesh Technique

In the present study, the hydrodynamic characteristics of underwater propulsors have been numerically investigated using a RANS flow solver based on pseudo-compressibility. A vertex-centered finite-volume method was utilized in conjunction with 2nd-order Roe’s FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing. The Spalart-Allmaras one equation model was employed for the closure of turbulence. A dual-time stepping method and the Gauss-Seidel iteration were used for unsteady time integration. An unstructured overset mesh technique was adopted to treat the relative motion between multiple bodies. Calculations were made for the DTRC4119 marine propeller at several advancing ratios. Additional calculations were also made for multiple-blade-row underwater propulsors. Reasonable agreements were obtained between the present results and the experiment for the pressure coefficients on the blade surface and the integrated blade loadings. The interaction between multiple blade rows and the thrust and torque distributions were also analyzed to investigate the performance of underwater propulsors.

Sound Radiation From Shear Deformable Stiffened Laminated Plates With Multiple Compliant Layers

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Xiongtao Cao ◽  
Hongxing Hua
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Plate Theory ◽  
Sound Radiation ◽  
Laminated Plates ◽  
Far Field ◽  
Frequency Range ◽  
First Order ◽  
Shear Deformable ◽  
Field Sound

Sound radiation from shear deformable stiffened laminated plates with multiple compliant layers is theoretically studied. Equations of motion for the composite laminated plates are on the basis of the first-order shear deformation plate theory, and the transfer matrix method is used to describe sound transmission through compliant layers. The first and second sets of stiffeners interact with the plate through normal line forces. By using the Fourier transform and stationary phase method, the far-field sound pressure is obtained in terms of analytical expressions. Comparisons are made between the first-order shear deformation plate theory and the classical thin plate theory. Three principal conclusions are drawn in the study. (1) The transverse point force acting on the stiffeners yields lower far-field sound pressure in the middle and high frequency range. Specifically, the transverse point force exerting on the large stiffeners produces the lowest far-field sound pressure among three different reactive points at the plate, small stiffener and large stiffener. (2) The far-field sound pressure spectra are confined by an acoustic circle and remain unchanged. Lots of flexural waves in the structure cannot radiate sound into the far field. (3) The sound attenuation of stiffened plates with compliant layers is mainly caused by the sound isolation of compliant layers rather than vibrational reduction. Compliant layers can effectively reduce the radiated sound pressure in the medium and high frequency range.

scholarly journals Development of a Balanced Adaptive Time-Stepping Strategy Based on an Implicit JFNK-DG Compressible Flow Solver

2021 ◽  
Author(s):  
Yu Pan ◽  
Zhen-Guo Yan ◽  
Joaquim Peiró ◽  
Spencer J. Sherwin
Keyword(s):  
High Efficiency ◽  
Total Error ◽  
Steady State Flow ◽  
Time Step ◽  
Spatial Error ◽  
Flow Solver ◽  
Time Stepping ◽  
Adaptive Time ◽  
Temporal And Spatial ◽  
Adaptive Time Stepping

AbstractA balanced adaptive time-stepping strategy is implemented in an implicit discontinuous Galerkin solver to guarantee the temporal accuracy of unsteady simulations. A proper relation between the spatial, temporal and iterative errors generated within one time step is constructed. With an estimate of temporal and spatial error using an embedded Runge-Kutta scheme and a higher order spatial discretization, an adaptive time-stepping strategy is proposed based on the idea that the time step should be the maximum without obviously influencing the total error of the discretization. The designed adaptive time-stepping strategy is then tested in various types of problems including isentropic vortex convection, steady-state flow past a flat plate, Taylor-Green vortex and turbulent flow over a circular cylinder at $${Re}=3\,900$$ Re = 3 900 . The results indicate that the adaptive time-stepping strategy can maintain that the discretization error is dominated by the spatial error and relatively high efficiency is obtained for unsteady and steady, well-resolved and under-resolved simulations.

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