scholarly journals Inverse Patch Transfer Functions Method as a Tool for Source Field Identification

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Dorian Vigoureux ◽  
Nicolas Totaro ◽  
Jonathan Lagneaux ◽  
Jean-Louis Guyader
Keyword(s):  
Background Noise ◽  
Experimental Validation ◽  
Transfer Functions ◽  
Near Field ◽  
Theoretical Background ◽  
Wall Pressure ◽  
Additional Measurement ◽  
Field Identification ◽  
Open Issue ◽  
Source Velocity

Many methods to detect, quantify, or reconstruct acoustic sources exist in the literature and are widely used in industry (near-field acoustic holography, inverse boundary element method, etc.). However, the source identification in a reverberant or nonanechoic environment on an irregularly shaped structure is still an open issue. In this context, the inverse patch transfer functions (iPTF) method first introduced by Aucejo et al. (2010, “Identification of Source Velocities on 3D Structures in Non-Anechoic Environments: Theoretical Background and Experimental Validation of the Inverse Patch Transfer Functions Method,” J. Sound Vib., 329(18), pp. 3691–3708) can be a suitable method. Indeed, the iPTF method has been developed to identify source velocity on complex geometries and in a nonanechoic environment. However, to obtain good results, the application of the method must follow rigorous criteria that were not fully investigated yet. In addition, as it was first defined, the iPTF method only provides source velocity while wall pressure or intensity should also give useful information to engineers. In the present article, a procedure to identify wall pressure and intensity of the source without any additional measurement is proposed. This procedure only needs simple numerical postprocessing. Using this new intensity identification, the influence of background noise, evanescent waves, and mesh discretization are illustrated on numerical examples. Finally, an experiment on a vibrating plate is shown to illustrate the iPTF procedure.

scholarly journals A Lab-Scale Experiment Approach to the Measurement of Wall Pressure from Near-Field under Water Explosions by a Hopkinson Bar

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xiongwei Cui ◽  
Xiongliang Yao ◽  
Yingyu Chen
Keyword(s):  
Shock Wave ◽  
Near Field ◽  
Underwater Explosion ◽  
Experimental System ◽  
Hopkinson Bar ◽  
Wall Pressure ◽  
Pressure Loading ◽  
Target Plate ◽  
Wave Pressure ◽  
Shock Wave Pressure

Direct measurement of the wall pressure loading subjected to the near-field underwater explosion is of great difficulty. In this article, an improved methodology and a lab-scale experimental system are proposed and manufactured to assess the wall pressure loading. In the methodology, a Hopkinson bar (HPB), used as the sensing element, is inserted through the hole drilled on the target plate and the bar’s end face lies flush with the loaded face of the target plate to detect and record the pressure loading. Furthermore, two improvements have been made on this methodology to measure the wall pressure loading from a near-field underwater explosion. The first one is some waterproof units added to make it suitable for the underwater environment. The second one is a hard rubber cylinder placed at the distal end, and a pair of ropes taped on the HPB is used to pull the HPB against the cylinder hard to ensure the HPB’s end face flushes with loaded face of the target plate during the bubble collapse. To validate the pressure measurement technique based on the HPB, an underwater explosion between two parallelly mounted circular target plates is used as the validating system. Based on the assumption that the shock wave pressure profiles at the two points on the two plates which are symmetrical to each other about the middle plane of symmetry are the same, it was found that the pressure obtained by the HPB was in excellent agreement with pressure transducer measurements, thus validating the proposed technique. To verify the capability of this improved methodology and experimental system, a series of minicharge underwater explosion experiments are conducted. From the recorded pressure-time profiles coupled with the underwater explosion evolution images captured by the HSV camera, the shock wave pressure loading and bubble-jet pressure loadings are captured in detail at 5  mm, 10  mm, …, 30  mm stand-off distances. Part of the pressure loading of the experiment at 35  mm stand-off distance is recorded, which is still of great help and significance for engineers. Especially, the peak pressure of the shock wave is captured.

Improved Analytical Models for Single- and Multi-layer Silver Superlenses

2009 ◽  
Vol 1182 ◽  
Author(s):  
Ciaran P Moore ◽  
Richard John Blaikie ◽  
Matthew D Arnold
Keyword(s):  
Transfer Functions ◽  
Near Field ◽  
Single Layer ◽  
Analytical Models ◽  
Full Field ◽  
Accurate Performance ◽  
Imaging Performance ◽  
Performance Estimates ◽  
Continuous Metal ◽  
Good Agreement

AbstractSpatial-frequency transfer functions are regularly used to model the imaging performance of near-field �superlens� systems. However, these do not account for interactions between the object that is being imaged and the superlens itself. As the imaging in these systems is in the near field, such interactions are important to consider if accurate performance estimates are to be obtained. We present here a simple analytical modification that can be made to the transfer function to account for near-field interactions for objects consisting of small apertures in otherwise-continuous metal screens. The modified transfer functions are evaluated by comparison with full-field finite-element simulations for representative single-layer and multi-layer silver superlenses, and good agreement is found.

scholarly journals Numerical simulations of near-field head-related transfer functions: Magnitude verification and validation with laser spark sources

2020 ◽  
Vol 148 (1) ◽  
pp. 153-166
Author(s):  
Sebastian T. Prepeliţă ◽  
Javier Gómez Bolaños ◽  
Ville Pulkki ◽  
Lauri Savioja ◽  
Ravish Mehra
Keyword(s):  
Numerical Simulations ◽  
Transfer Functions ◽  
Near Field ◽  
Verification And Validation ◽  
Laser Spark

Calculation and Analysis of Near-Field Head-Related Transfer Functions from a Simplified Head-Neck-Torso Model

2012 ◽  
Vol 29 (3) ◽  
pp. 034302 ◽  
Author(s):  
Ze-Wei Chen ◽  
Guang-Zheng Yu ◽  
Bo-Sun Xie ◽  
Shan-Qun Guan
Keyword(s):  
Transfer Functions ◽  
Near Field ◽  
Torso Model ◽  
Head Neck

scholarly journals Near-Field to Far-Field Transformation Techniques with Spiral Scannings: A Comprehensive Review

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Renato Cicchetti ◽  
Francesco D’Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
...  
Keyword(s):  
Communication Systems ◽  
Near Field ◽  
Theoretical Background ◽  
Wireless Communication Systems ◽  
Far Field ◽  
Unified Theory ◽  
Transformation Techniques ◽  
Positioning Systems ◽  
Rotational Surface ◽  
Spiral Scanning

An overview of the near-field-far-field (NF-FF) transformation techniques with innovative spiral scannings, useful to derive the radiation patterns of the antennas commonly employed in the modern wireless communication systems, is provided in this paper. The theoretical background and the development of a unified theory of the spiral scannings for quasi-spherical and nonspherical antennas are described, and an optimal sampling interpolation expansion to evaluate the probe response on a quite arbitrary rotational surface from a nonredundant number of its samples, collected along a proper spiral wrapping it, is presented. This unified theory can be applied to spirals wrapping the conventional scanning surfaces and makes it possible to accurately reconstruct the NF data required by the NF-FF transformation employing the corresponding classical scanning. A remarkable reduction of the measurement time is so achieved, due to the use of continuous and synchronized movements of the positioning systems and to the reduced number of needed NF measurements. Some numerical and experimental results relevant to the spherical spiral scanning case when dealing with quasi-planar and electrically long antennas are shown.

Near-Field Virtual Audio Displays

2002 ◽  
Vol 11 (1) ◽  
pp. 93-106 ◽  
Author(s):  
Douglas S. Brungart
Keyword(s):  
Transfer Functions ◽  
Near Field ◽  
Multimodal Interfaces ◽  
Sound Sources ◽  
Auditory Cues ◽  
Current State ◽  
Potential Applications ◽  
Technical Challenges ◽  
State Of Research ◽  
Virtual Audio

Although virtual audio displays are capable of realistically simulating relatively distant sound sources, they are not yet able to accurately reproduce the spatial auditory cues that occur when sound sources are located near the listener's head. Researchers have long recognized that the binaural difference cues that dominate auditory localization are independent of distance beyond 1 m but change systematically with distance when the source approaches with in 1 m of the listener's head. Recent research has shown that listeners are able to use these binaural cues to determine the distances of nearby sound sources. However, technical challenges in the collection and processing of near-field head-related transfer functions (HRTFs) have thus far prevented the construction of a fully functional near-field audio display. This paper summarizes the current state of research in the localization of nearby sound sources and outlines the technical challenges involved in the creation of a near-field virtual audio display. The potential applications of near-field displays in immersive virtual environments and multimodal interfaces are also discussed.

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