36,135 research outputs found
High-order, Dispersionless "Fast-Hybrid" Wave Equation Solver. Part I: Sampling Cost via Incident-Field Windowing and Recentering
This paper proposes a frequency/time hybrid integral-equation method for the
time dependent wave equation in two and three-dimensional spatial domains.
Relying on Fourier Transformation in time, the method utilizes a fixed
(time-independent) number of frequency-domain integral-equation solutions to
evaluate, with superalgebraically-small errors, time domain solutions for
arbitrarily long times. The approach relies on two main elements, namely, 1) A
smooth time-windowing methodology that enables accurate band-limited
representations for arbitrarily-long time signals, and 2) A novel Fourier
transform approach which, in a time-parallel manner and without causing
spurious periodicity effects, delivers numerically dispersionless
spectrally-accurate solutions. A similar hybrid technique can be obtained on
the basis of Laplace transforms instead of Fourier transforms, but we do not
consider the Laplace-based method in the present contribution. The algorithm
can handle dispersive media, it can tackle complex physical structures, it
enables parallelization in time in a straightforward manner, and it allows for
time leaping---that is, solution sampling at any given time at
-bounded sampling cost, for arbitrarily large values of ,
and without requirement of evaluation of the solution at intermediate times.
The proposed frequency-time hybridization strategy, which generalizes to any
linear partial differential equation in the time domain for which
frequency-domain solutions can be obtained (including e.g. the time-domain
Maxwell equations), and which is applicable in a wide range of scientific and
engineering contexts, provides significant advantages over other available
alternatives such as volumetric discretization, time-domain integral equations,
and convolution-quadrature approaches.Comment: 33 pages, 8 figures, revised and extended manuscript (and now
including direct comparisons to existing CQ and TDIE solver implementations)
(Part I of II
Acoustic modeling using the digital waveguide mesh
The digital waveguide mesh has been an active area of music acoustics research for over ten years. Although founded in 1-D digital waveguide modeling, the principles on which it is based are not new to researchers grounded in numerical simulation, FDTD methods, electromagnetic simulation, etc. This article has attempted to provide a considerable review of how the DWM has been applied to acoustic modeling and sound synthesis problems, including new 2-D object synthesis and an overview of recent research activities in articulatory vocal tract modeling, RIR synthesis, and reverberation simulation. The extensive, although not by any means exhaustive, list of references indicates that though the DWM may have parallels in other disciplines, it still offers something new in the field of acoustic simulation and sound synth
Systems control theory applied to natural and synthetic musical sounds
Systems control theory is a far developped field which helps to study stability, estimation and control of dynamical systems. The physical behaviour of musical instruments, once described by dynamical systems, can then be controlled and numerically simulated for many purposes.
The aim of this paper is twofold: first, to provide the theoretical background on linear system theory, both in continuous and discrete time, mainly in the case of a finite number of degrees of freedom ; second, to give illustrative examples on wind instruments, such as the vocal tract represented as a waveguide, and a sliding flute
Fast and Accurate Simulation Technique for Large Irregular Arrays
A fast full-wave simulation technique is presented for the analysis of large
irregular planar arrays of identical 3-D metallic antennas. The solution method
relies on the Macro Basis Functions (MBF) approach and an interpolatory
technique to compute the interactions between MBFs. The Harmonic-polynomial
(HARP) model is established for the near-field interactions in a modified
system of coordinates. For extremely large arrays made of complex antennas, two
approaches assuming a limited radius of influence for mutual coupling are
considered: one is based on a sparse-matrix LU decomposition and the other one
on a tessellation of the array in the form of overlapping sub-arrays. The
computation of all embedded element patterns is sped up with the help of the
non-uniform FFT algorithm. Extensive validations are shown for arrays of
log-periodic antennas envisaged for the low-frequency SKA (Square Kilometer
Array) radio-telescope. The analysis of SKA stations with such a large number
of elements has not been treated yet in the literature. Validations include
comparison with results obtained with commercial software and with experiments.
The proposed method is particularly well suited to array synthesis, in which
several orders of magnitude can be saved in terms of computation time.Comment: The paper was submitted to IEEE Transaction on Antennas and
Propagation on 01 - Feb.- 2017. The paper is 12 pages with 18 figure
Reconstruction of shapes and refractive indices from backscattering experimental data using the adaptivity
We consider the inverse problem of the reconstruction of the spatially
distributed dielectric constant $\varepsilon_{r}\left(\mathbf{x}\right), \
\mathbf{x}\in \mathbb{R}^{3}n\left(\mathbf{x}\right) =\sqrt{\varepsilon_{r}\left(\mathbf{x}\right)}.\varepsilon_{r}\left(\mathbf{x}\right) $ is reconstructed using a
two-stage reconstruction procedure. In the first stage an approximately
globally convergent method proposed is applied to get a good first
approximation of the exact solution. In the second stage a locally convergent
adaptive finite element method is applied, taking the solution of the first
stage as the starting point of the minimization of the Tikhonov functional.
This functional is minimized on a sequence of locally refined meshes. It is
shown here that all three components of interest of targets can be
simultaneously accurately imaged: refractive indices, shapes and locations
An Efficient Framework For Fast Computer Aided Design of Microwave Circuits Based on the Higher-Order 3D Finite-Element Method
In this paper, an efficient computational framework for the full-wave design by optimization of complex microwave passive devices, such as antennas, filters, and multiplexers, is described. The framework consists of a computational engine, a 3D object modeler, and a graphical user interface. The computational engine, which is based on a finite element method with curvilinear higher-order tetrahedral elements, is coupled with built-in or external gradient-based optimization procedures. For speed, a model order reduction technique is used and the gradient computation is achieved by perturbation with geometry deformation, processed on the level of the individual mesh nodes. To maximize performance, the framework is targeted to multicore CPU architectures and its extended version can also use multiple GPUs. To illustrate the accuracy and high efficiency of the framework, we provide examples of simulations of a dielectric resonator antenna and full-wave design by optimization of two diplexers involving tens of unknowns, and show that the design can be completed within the duration of a few simulations using industry-standard FEM solvers. The accuracy of the design is confirmed by measurements
Efficient Synthesis of Room Acoustics via Scattering Delay Networks
An acoustic reverberator consisting of a network of delay lines connected via
scattering junctions is proposed. All parameters of the reverberator are
derived from physical properties of the enclosure it simulates. It allows for
simulation of unequal and frequency-dependent wall absorption, as well as
directional sources and microphones. The reverberator renders the first-order
reflections exactly, while making progressively coarser approximations of
higher-order reflections. The rate of energy decay is close to that obtained
with the image method (IM) and consistent with the predictions of Sabine and
Eyring equations. The time evolution of the normalized echo density, which was
previously shown to be correlated with the perceived texture of reverberation,
is also close to that of IM. However, its computational complexity is one to
two orders of magnitude lower, comparable to the computational complexity of a
feedback delay network (FDN), and its memory requirements are negligible
Simulation of Single Reed Instruments Oscillations Based on Modal Decomposition of Bore and Reed Dynamics
This paper investigates the sound production in a system made of a bore
coupled with a reed valve. Extending previous work (Debut, 2004), the input
impedance of the bore is projected on the modes of the air column. The acoustic
pressure is therefore calculated as the sum of modal components. The
airrrflow blown into the bore is modulated by reed motion, assuming
the reed to be a single degree of freedom oscillator. Calculation of
self-sustained oscillations controlled by time-varying mouth pressure and
player's embouchure parameter is performed using ODE solvers. Results emphasize
the par ticipation of the whole set of components in the mode locking process.
Another impor tant feature is the mutual innnfluence of reed and
bore resonance during growing blowing pressure transients, oscillation
threshold being altered by the reed natural frequency and the reed damping.
Steady-state oscillations are also investigated and compared with results given
by harmonic balance method and by digital sound synthesis
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