Reconstruction of Three-Dimensional Sound Field from Two-Dimensional Sound Field Using Optical Computerized Tomography and Near-Field Acoustical Holography

2009 ◽  
Vol 48 (7) ◽  
pp. 07GC03 ◽  
Author(s):  
Takeshi Ohbuchi ◽  
Koichi Mizutani ◽  
Naoto Wakatsuki ◽  
Kojiro Nishimiya ◽  
Hiroyuki Masuyama
Keyword(s):  
Computerized Tomography ◽  
Near Field ◽  
Three Dimensional ◽  
Sound Field ◽  
Two Dimensional ◽  
Acoustical Holography

Corrugated SNOM probe with enhanced energy throughput

2008 ◽  
Vol 16 (4) ◽  
Author(s):  
T. Antosiewicz ◽  
T. Szoplik
Keyword(s):  
Near Field ◽  
Three Dimensional ◽  
Energy Output ◽  
Dipolar Field ◽  
Two Dimensional ◽  
The Core ◽  
Dimensional Approximation ◽  
New Type ◽  
Difference Time ◽  
Main Factor

AbstractIn a previous paper we proposed a modification of metal-coated tapered-fibre aperture probes for scanning near-field optical microscopes (SNOMs). The modification consists in radial corrugations of the metal-dielectric interface oriented inward the core. Their purpose is to facilitate the excitation of surface plasmons, which increase the transport of energy beyond the cut-off diameter and radiate a quasi-dipolar field from the probe output rim. An increase in energy output allows for reduction of the apex diameter, which is the main factor determining the resolution of the microscope. In two-dimensional finite-difference time-domain (FDTD) simulations we analyse the performance of the new type of SNOM probe. We admit, however, that the two-dimensional approximation gives better results than expected from exact three-dimensional ones. Nevertheless, optimisation of enhanced energy throughput in corrugated probes should lead to at least twice better resolution with the same sensitivity of detectors available nowadays.

Simulation and experimental investigations for the patch near-field acoustical holography

2008 ◽  
Vol 222 (6) ◽  
pp. 945-953 ◽  
Author(s):  
C Yang ◽  
J Chen ◽  
J Q Li ◽  
W F Xue
Keyword(s):  
Fourier Transform ◽  
Sound Pressure ◽  
Near Field ◽  
Sound Field ◽  
Experimental Investigations ◽  
Regularization Methods ◽  
Aperture Size ◽  
Measurement Surface ◽  
Physical Necessity ◽  
Acoustical Holography

In order to reconstruct the sound field, the fast Fourier transform (FFT)-based near-field acoustical holography (NAH) demands that the measurement surface must extend to a region where the sound pressure decreases to a low level. This method is unfit for reconstructing the partial sound field in which the measurement aperture size is limited either by physical necessity or as a way of reducing the measurement cost. Statistically optimal NAH (SONAH) performs plane-to-plane calculations directly in the spatial domain, avoids all errors occurred in the FFT-based NAH and significantly increases the accuracy of the reconstruction of the partial sound field. In the present work, combined with the different regularization methods, SONAH is performed for reconstructing the partial sound field. The errors over the central and the peripheral sections of the reconstruction area are researched separately. Simulations and experiments show that SONAH is successful in reconstructing the partial sound field and the errors over the central sections are smaller than that over the peripheral sections. Experiments demonstrate that Tikhonov regularization in conjunction with Engl's criterion is suitable for the reconstruction of the practical sound field.

scholarly journals The principle of statistically optimal planar near-field acoustical holography and the sound field separation technique

2005 ◽  
Vol 54 (3) ◽  
pp. 1253 ◽  
Author(s):  
Li Wei-Bing ◽  
Chen Jian ◽  
Yu Fei ◽  
Bi Chuan-Xing ◽  
Chen Xin-Zhao
Keyword(s):  
Near Field ◽  
Sound Field ◽  
Separation Technique ◽  
Acoustical Holography ◽  
Field Separation

Near-field acoustical holography incorporating compressive sampling: Effect of measurement distance and array density

2020 ◽  
Vol 68 (6) ◽  
pp. 470-489
Author(s):  
Tongyang Shi ◽  
Weimin Thor ◽  
J. Stuart Bolton
Keyword(s):  
Sound Source ◽  
Near Field ◽  
Source Region ◽  
Sampling Rate ◽  
Sound Field ◽  
Compressive Sampling ◽  
Sound Power ◽  
L1 Norm ◽  
Measured Intensity ◽  
Acoustical Holography

To identify sound source locations and strength by using near-field acoustical holography (NAH), many microphones are generally required in order to span the source region and to ensure a sufficiently high spatial sampling rate. It is often the case that hundreds of microphones are needed, so such measurements are costly, which has limited the application of NAH in industrial settings. Recently, however, it has been shown that it is possible to accurately identify concentrated sound sources with a limited number of microphones based on compressive sampling theory. Here, the theory of the four NAH methods that were studied in the present work, that is, statistically optimized near-field acoustical holography (SONAH), wideband acoustical holography (WBH), l1-norm minimization, and a hybrid compressive sampling method, is briefly reviewed. Note that the latter three procedures incorporate elements of compressive sampling. Then, a simulation with one monopole as the sound source was conducted to illustrate some basic characteristics of these algorithms. In the experimental portion of the work, a multi-element loudspeaker was used as the sound source. A near-field intensity scan was conducted to measure both the true intensity spatial distribution and the sound power generated by the loudspeaker to provide a basis against which the values obtained from the holography reconstructions could be compared. The sound field was reconstructed by using both near- and far-field measurements, and the number of microphone measurements used to reconstruct the sound field was systematically decreased by increasing the spacing between microphones. Both in the simulation and experiment, the sound field was reconstructed by using the four NAH methods mentioned above. Then, the reconstruction results were comparedwith the measured intensity results in terms of spatial localization and sound power, and the benefits of the compressive sampling approach are illustrated.

Prediction of Rail and Bridge Noise in Near- and Far-Field: A Combined 2.5-Dimensional and Two-Dimensional Method

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
X. D. Song ◽  
Q. Li ◽  
D. J. Wu
Keyword(s):  
Interaction Analysis ◽  
Near Field ◽  
Three Dimensional ◽  
Shielding Effect ◽  
Far Field ◽  
Acoustic Model ◽  
Two Dimensional ◽  
Box Girder ◽  
Total Noise ◽  
Field Noise

Bridge noise and rail noise induced by passing trains should be included while estimating low- and medium-frequency (20–1000 Hz) noise in railway viaducts. However, the prediction of bridge noise and rail noise using a three-dimensional (3D) acoustic model is not efficient, especially for far-field points. In this study, a combined 2.5-dimensional (2.5D) and two-dimensional (2D) method is proposed to predict bridge noise and rail noise in both the near- and far-field. First, the near-field noise is obtained by combining the 2.5D acoustic model and a 3D vehicle–track–bridge interaction analysis. Then, the 2D method is used to estimate the attenuation of bridge noise and rail noise in the far-field, and the accuracy is validated through comparison with the 2.5D method. Third, the near-field points are treated as reference sources, and the noise at far-field points is predicted by combining the 2.5D and 2D methods. Finally, the proposed method is used to predict the bridge noise and rail noise for a box girder and a U-shaped girder. The spatial distribution of the bridge noise and rail noise is investigated. Generally, the rail noise is dominant above the bridge, and the bridge noise has a larger contribution to the total noise beneath the bridge. The rail noise from the U-shaped girder is much smaller than that from the box girder due to the shielding effect of the webs.

Development of Near-Field Acoustical Holograph and its Review

2014 ◽  
Vol 971-973 ◽  
pp. 1598-1601
Author(s):  
Xu Liu ◽  
Xiao Qin Liu ◽  
Chang Liu
Keyword(s):  
Near Field ◽  
Sound Field ◽  
Separation Technique ◽  
Acoustic Holography ◽  
Noise Sources ◽  
Engineering Applications ◽  
Powerful Technique ◽  
Experiment And Simulation ◽  
Acoustical Holography ◽  
Field Separation

Near-field acoustic holography (NAH) is a powerful technique for identifying noise sources and visualizing acoustic field.The theory and algorithm of NAH techniques are introduced , and it is proved by experiment and simulation. The researches on near field acoustical holography (NAH) are reviewed，including the sound field separation technique and Patch NAH technique arisen in recent years.The difficulties in NAH and research on current situations are discussed , Finally,some engineering applications are introduced by detailed examples.

scholarly journals Two-dimensional Talbot effect of the optical vortices and their spatial evolution

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Denis A. Ikonnikov ◽  
Sergey A. Myslivets ◽  
Mikhail N. Volochaev ◽  
Vasily G. Arkhipkin ◽  
Andrey M. Vyunishev
Keyword(s):  
Spatial Configuration ◽  
Near Field ◽  
Three Dimensional ◽  
Visible Range ◽  
Optical Vortices ◽  
Spatial Evolution ◽  
Self Healing ◽  
Two Dimensional ◽  
Talbot Effect ◽  
Wide Range

AbstractWe report on the experimental and theoretical study of the near-field diffraction of optical vortices (OVs) at a two-dimensional diffraction grating. The Talbot effect for the optical vortices in the visible range is experimentally observed and the respective Talbot carpets for the optical vortices are experimentally obtained for the first time. It is shown that the spatial configuration of the light field behind the grating represents a complex three-dimensional lattice of beamlet-like optical vortices. A unit cell of the OV lattice is reconstructed using the experimental data and the spatial evolution of the beamlet intensity and phase singularities of the optical vortices is demonstrated. In addition, the self-healing effect for the optical vortices, which consists in flattening of the central dip in the annular intensity distribution, i.e., restoring the image of the object plane predicted earlier is observed. The calculated results agree well with the experimental ones. The results obtained can be used to create and optimize the 3D OV lattices for a wide range of application areas.

An efficient design method for LED surface sources in three-dimensional rotational geometry using projected angle difference  An efficient design method for LED surface sources

2018 ◽  
Vol 51 (3) ◽  
pp. 457-464 ◽  
Author(s):  
X Li ◽  
P Ge ◽  
H Wang
Keyword(s):  
Design Method ◽  
Near Field ◽  
Three Dimensional ◽  
Optical Systems ◽  
Two Dimensional ◽  
Efficient Design ◽  
Angle Difference ◽  
Extended Sources ◽  
The Relationship ◽  
Better Than

An efficient method is proposed for the design of prescribed rotational illumination on the far or near field using the edge-ray principle. By this method, the prescribed illuminance on the prescribed location can be determined by projected angle difference in a two-dimensional design process for LED extended sources. Profiles of the lens with two initial curves on the centre can be calculated based on the relationship between the illuminance and the projected angle difference. The initial optical systems we calculated are close to the prescribed illumination despite the influence of skew rays. More importantly, a prescribed illumination on the near field can be achieved accurately and quickly by using this method, which is better than the usual luminous intensity distribution design methods for LED extended sources.

Three-Dimensional CT Imaging of the Wrist

1992 ◽  
Vol 17 (5) ◽  
pp. 504-506 ◽  
Author(s):  
S. E. JAMES ◽  
R. RICHARDS ◽  
D. A. McGROUTHER
Keyword(s):  
Computerized Tomography ◽  
Three Dimensional ◽  
Ct Images ◽  
Two Dimensional ◽  
Radiological Imaging ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Raw Data ◽  
Three Dimensional Imaging ◽  
New Approach

Three-dimensional computerized tomography provides a new approach to radiological imaging. Raw data from sequential two-dimensional scans have been reconstructed as a three-dimensional model of the carpal area using the Medical Graphics and Imaging Workstation. This study demonstrates the anatomical accuracy and potential diagnostic qualities of a reconstruction of the carpus using this system. The advantages, pitfalls and suggested applications of this technique of carpal imaging are discussed. Three-dimensional imaging is shown to provide a great deal of information which cannot be viewed on conventional radiographs or CT images.

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