5,808 research outputs found
FDTD/K-DWM simulation of 3D room acoustics on general purpose graphics hardware using compute unified device architecture (CUDA)
The growing demand for reliable prediction of sound fields in rooms have resulted in adaptation of various approaches for physical modeling, including the Finite Difference Time Domain (FDTD) and the Digital Waveguide Mesh (DWM). Whilst considered versatile and attractive methods, they suffer from dispersion errors that increase with frequency and vary with direction of propagation, thus imposing a high frequency calculation limit. Attempts have been made to reduce such errors by considering different mesh topologies, by spatial interpolation, or by simply oversampling the grid. As the latter approach is computationally expensive, its application to three-dimensional problems has often been avoided. In this paper, we propose an implementation of the FDTD on general purpose graphics hardware, allowing for high sampling rates whilst maintaining reasonable calculation times. Dispersion errors are consequently reduced and the high frequency limit is increased. A range of graphics processors are evaluated and compared with traditional CPUs in terms of accuracy, calculation time and memory requirements
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
Optical resonators based on Bloch surface waves
A few recent works suggest the possibility of controlling light propagation
at the interface of periodic multilayers supporting Bloch surface waves (BSWs),
but optical resonators based on BSWs are yet to demonstrate. Here we discuss
the feasibility of exploiting guided BSWs in a ring resonator configuration. In
particular, we investigate the main issues related to the design of these
structures, and we discuss about their limitations in terms of quality factors
and dimensions. We believe these results might be useful for the development of
a complete BSW-based platform for application ranging from optical sensing to
the study of the light-matter interaction in micro and nano structures.Comment: 10 pages, 10 figures. To be published in JOSA
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
A novel boundary element method using surface conductive absorbers for full-wave analysis of 3-D nanophotonics
Fast surface integral equation (SIE) solvers seem to be ideal approaches for
simulating 3-D nanophotonic devices, as these devices generate fields both in
an interior channel and in the infinite exterior domain. However, many devices
of interest, such as optical couplers, have channels that can not be terminated
without generating reflections. Generating absorbers for these channels is a
new problem for SIE methods, as the methods were initially developed for
problems with finite surfaces. In this paper we show that the obvious approach
for eliminating reflections, making the channel mildly conductive outside the
domain of interest, is inaccurate. We describe a new method, in which the
absorber has a gradually increasing surface conductivity; such an absorber can
be easily incorporated in fast integral equation solvers. Numerical experiments
from a surface-conductivity modified FFT-accelerated PMCHW-based solver are
correlated with analytic results, demonstrating that this new method is orders
of magnitude more effective than a volume absorber, and that the smoothness of
the surface conductivity function determines the performance of the absorber.
In particular, we show that the magnitude of the transition reflection is
proportional to 1/L^(2d+2), where L is the absorber length and d is the order
of the differentiability of the surface conductivity function.Comment: 10 page
3D-FDTD Method for Analysis of Rectangular Waveguide Loaded with Anisotropic Dielectric Material
One of the most popular techniques to solve electromagneticproblems numerically is using finite-difference timedomain(FDTD) method. The method has been successfullyapplied to an extremely wide variety of electromagnetic problems.The essential reason resides in the fact that the FDTD methoditself is extremely simple even for analyzing in a three-dimensional(3D) system. In this paper, the analysis of resonant frequencyfor a rectangular waveguide which is loaded with anisotropicdielectric material is numerically investigated based on 3D-FDTDmethod. The wave equations and modes that appear in thewaveguide are analyzed theoretically in which the results areapplied to validate the numerical result obtained from 3D-FDTDmethod. For comparison, an empty rectangular waveguide anda rectangular waveguide fully loaded with isotropic dielectricmaterial are also analyzed both theoretically and numerically.From the result, it shows that a good agreement has been achievedbetween theoretical calculation and 3D-FDTD numerical resultswith their discrepancies of 0.26â2.32%
3D-FDTD Method for Analysis of Rectangular Waveguide Loaded with Anisotropic Dielectric Material
One of the most popular techniques to solve electromagneticproblems numerically is using finite-difference timedomain(FDTD) method. The method has been successfullyapplied to an extremely wide variety of electromagnetic problems.The essential reason resides in the fact that the FDTD methoditself is extremely simple even for analyzing in a three-dimensional(3D) system. In this paper, the analysis of resonant frequencyfor a rectangular waveguide which is loaded with anisotropicdielectric material is numerically investigated based on 3D-FDTDmethod. The wave equations and modes that appear in thewaveguide are analyzed theoretically in which the results areapplied to validate the numerical result obtained from 3D-FDTDmethod. For comparison, an empty rectangular waveguide anda rectangular waveguide fully loaded with isotropic dielectricmaterial are also analyzed both theoretically and numerically.From the result, it shows that a good agreement has been achievedbetween theoretical calculation and 3D-FDTD numerical resultswith their discrepancies of 0.26â2.32%
High-accuracy adaptive modeling of the energy distribution of a meniscus-shaped cell culture in a Petri dish
Cylindrical Petri dishes embedded in a rectangular waveguide and exposed to a polarized electromagnetic wave are often used to grow cell cultures. To guarantee the success of these cultures, it is necessary to enforce that the specific absorption rate distribution is sufficiently high and uniform over the Petri dish. Accurate numerical simulations are needed to design such systems. These simulations constitute a challenge due to the strong discontinuity of electromagnetic material properties involved, the relative low field value within the dish cultures compared with the rest of the domain, and the presence of the meniscus shape developed at the liquid boundary. The latter greatly increases the level of complexity of the model in terms of geometry and intensity of the gradients/singularities of the field solution. In here, we employ a three-dimensional (3D) hp-adaptive finite element method using isoparametric elements to obtain highly accurate simulations. We analyze the impact of the geometrical modeling of the meniscus shape cell culture in the hp-adaptivity. Numerical results showing the error convergence history indicate the numerical difficulties arisen due to the presence of a meniscus-shaped object. At the same time, the resulting energy distribution shows that to consider such meniscus shape is essential to guarantee the success of the cell culture from the biological point of view
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