Real time sound field visualization in the near field, far field and at absorbing surfaces

2008 ◽  
Vol 123 (5) ◽  
pp. 3439-3439
Author(s):  
Hans‐Elias De Bree ◽  
Emiel Tijs ◽  
Tom Basten
Keyword(s):  
Real Time ◽  
Near Field ◽  
Sound Field ◽  
Far Field

scholarly journals Investigation on Wireless Link for Medical Telemetry Including Impedance Matching of Implanted Antennas

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1431
Author(s):  
Ilkyu Kim ◽  
Sun-Gyu Lee ◽  
Yong-Hyun Nam ◽  
Jeong-Hae Lee
Keyword(s):  
Real Time ◽  
Human Body ◽  
Near Field ◽  
Impedance Matching ◽  
The Body ◽  
Field Pattern ◽  
Communication Link ◽  
Far Field ◽  
Antenna Coupling ◽  
Medical Telemetry

The development of biomedical devices benefits patients by offering real-time healthcare. In particular, pacemakers have gained a great deal of attention because they offer opportunities for monitoring the patient’s vitals and biological statics in real time. One of the important factors in realizing real-time body-centric sensing is to establish a robust wireless communication link among the medical devices. In this paper, radio transmission and the optimal characteristics for impedance matching the medical telemetry of an implant are investigated. For radio transmission, an integral coupling formula based on 3D vector far-field patterns was firstly applied to compute the antenna coupling between two antennas placed inside and outside of the body. The formula provides the capability for computing the antenna coupling in the near-field and far-field region. In order to include the effects of human implantation, the far-field pattern was characterized taking into account a sphere enclosing an antenna made of human tissue. Furthermore, the characteristics of impedance matching inside the human body were studied by means of inherent wave impedances of electrical and magnetic dipoles. Here, we demonstrate that the implantation of a magnetic dipole is advantageous because it provides similar impedance characteristics to those of the human body.

Realtime Wellbore Digitalization for Stimulations Using Multi-Well Fiber Optics

2021 ◽  
Author(s):  
Xinyang Li ◽  
Andres J. Chavarria ◽  
Yassine Oukaci
Keyword(s):  
Real Time ◽  
Fiber Optics ◽  
Near Field ◽  
Fracture Propagation ◽  
Field Strain ◽  
Far Field ◽  
Time Data ◽  
Strain Measurements ◽  
Well Stimulation ◽  
Time Operation

Abstract Distributed Fiber-optic Sensing (DFOS) provides real-time data acquisition, monitoring and diagnostics for well stimulation and well spacing assessment. These include measurements of Distributed Acoustic Sensing (DAS) with high frequency acoustics in treatment wells, and low frequency strain/temperature sensing in offset monitor ones. The goal of this integrated study is to show the value of multi-well fiber sensing for real time fracturing diagnostics and stimulation optimization. By integrating near field injection to far field strain responses we assess overall reservoir development. The availability of fibers on both the treatment well and a nearby observation well allows us to investigate the near-wellbore injection profile and the far-field strain fracture propagation. Quantitative strain levels clearly respond to the effects of well distance, location and treatment well stimulation design. Monitoring well strain measurements of fracture density and triggered stimulated span were logged and compared to acoustic signals in the nearfield stage by stage. DAS interpretation was conducted during the treatment of each stage indicating the effectiveness and efficiency of the completion design. Results show that this is a very effective tool to better understand the performance of the fracturing treatment by digital transformation using DAS data. In addition, acoustic and strain measurements also validated its diagnostic capability for real-time operation monitoring. In this presentation we show how the near-field acoustic and far-field strain measurements allow for better understanding of the completion efficiency. This is by assessing the far field response to quantified DAS injected signals in the treatment. This analysis takes advantage of fiber installation on both the treatment and nearby monitor well. The fluid and proppant allocations in the near field were performed on the treatment well using relative acoustic intensities. Meanwhile, the fracture propagation induced strain change is recorded by the offset fiber well. Using this fiber data reveals dominant clusters and stage bias from near-field injection profile. Simultaneously the far-field identified fracture counts from strain further enable a geomechanical assessment of the stimulated reservoir and assess the effectiveness of the completion design. Multiple DAS fiber equipped wells not only provide single diagnostic tool for each of the fiber well, but also demonstrate significant integrated assessment of the stimulation effectiveness, completion efficiency, well interaction, and reservoir description. Availability of near and far field measurements constitutes an important tool to assess properties of the reservoir. Here we show how different vantage points can help illuminate a fracturing program in unconventional reservoirs.

Integrated “CFD - Acoustic” Computational Approach to the Simulation of Aircraft Fan Noise

2014 ◽  
Author(s):  
Piergiorgio Ferrante ◽  
Paolo di Francescantonio ◽  
Pierre-Alain Hoffer ◽  
Stéphane Vilmin ◽  
Charles Hirsch
Keyword(s):  
Unsteady Flow ◽  
Sound Propagation ◽  
Noise Source ◽  
Acoustic Radiation ◽  
Near Field ◽  
Sound Field ◽  
Computational Approach ◽  
Far Field ◽  
Fan Noise ◽  
Field Noise

An innovative computational approach, integrating mesh generation, CFD simultaneous analysis of noise source and propagation, with acoustic radiation, is presented and applied to the simulation of the Advanced Noise Control Fan (ANCF) developed by NASA Glenn Research Center. The tonal noise source and the sound propagation in the nacelle duct and in the nacelle near field are simultaneously predicted, starting from the engine geometry and parameters, with a single CFD analysis based on an efficient Nonlinear Harmonic (NLH) method. The sound radiation to the far field is computed with the Green’s function approach implemented in a BEM frequency domain solver of the convective Helmholtz equation. The present method provides to a gain of close to two orders of magnitude compared to standard approaches, based on full unsteady flow simulations, followed by a near-field FEM based approach and a BEM method for the far-field noise propagation. The final comparison between the numerical results and the measurements highlights the capability of the methodology to efficiently predict the unsteady flow field and the radiated sound field.

The structure of rotating sound fields

1993 ◽  
Vol 440 (1909) ◽  
pp. 257-271 ◽  
Keyword(s):  
Near Field ◽  
Azimuthal Angle ◽  
Sound Field ◽  
Evanescent Waves ◽  
Source Distribution ◽  
Dimensional Structure ◽  
Main Beam ◽  
Far Field ◽  
Contour Plots ◽  
Radiation Zone

An account is given of the three-dimensional structure of the sound field produced by a spinning sinusoidal distribution of thickness or loading sources. Particular attention is paid to the creeping evanescent waves in the near field and their physical interpretation as trapped edge waves; an exponentially small amount of energy leaks or tunnels through them to emerge as far-field acoustic radiation (as it does through the inhomogeneous waves carried by a waveguide in a cylindrically layered medium). The dependence of the structure on three parameters is investigated in detail: the Mach number M at the outermost radius of the source; the harmonic number n , defined so that the source strength is a function of nθ , where θ denotes azimuthal angle; and the type of source, i. e. thickness or loading. Parameter values considered include those for subsonic, sonic and supersonic motion, and for high and low harmonics. The field is calculated by reducing a special case of Rayleigh’s double integral to a single integral containing a function related to the Chebyshev polynomials, then integrating numerically to give contour plots of pressure as a function of position on various plane and cylindrical sections. These show that the evanescent waves occupy a spherical or ellipsoidal region, and consist of crescents of alternating high and low pressure, shaped and arranged like the segments of an orange; its ‘peel’ marks the transition to the propagating spiral waves of the far field, i. e. the radiation zone. Contour plots on meridional sections are similar to those for the oscillating hertzian electric dipole, suggesting that the field is approximately that produced by a suitably phased arrangement of its acoustic counterpart. When M > 1, the source distribution straddles both the evanescent and the radiation zone; at high supersonic M , the meridional contour plots display an intense beaming pattern, with side-lobes between the main beam and source plane. The results of the paper agree with previous work on propeller acoustics, especially the asymptotic theory.

Reconstruction of Sound Field Based on Mono-Poles Array Modes

2012 ◽  
Vol 226-228 ◽  
pp. 316-319
Author(s):  
Yong Fa Nie ◽  
Hai Chao Zhu ◽  
Rong Fu Mao
Keyword(s):  
Acoustic Field ◽  
Near Field ◽  
Single Point ◽  
Sound Field ◽  
Far Field ◽  
Acoustic Source ◽  
Radiation Mode ◽  
Field Reconstruction ◽  
Radiation Noise ◽  
Phase Angles

To effectively reduce radiation noise of the structures, the information detailed of the acoustic field is required. An approach of acoustic field reconstruction based mono-poles array modes is developed. The acoustic source is expressed as the form of some mono-poles array superposition which is defined as mono-poles array radiation mode. The amplitudes of these mono-poles are equal and their phase angles are in phase or out of phase in each array form. The amplitudes of mono-poles array modes are obtained by means of the complex pressures measured in near field, and then the whole acoustic field can be reconstructed. Feasibility of this approach is verified through a numerical example of a single-point harmonic excited and simple supported plate and the error analysis shows that the near field reconstruction result is accurate and the far field reconstruction result is more accurate.

Magnetic Tag Antenna for UHF Near-field and Far-Field RFID Applications

2015 ◽  
Vol 5 (2) ◽  
pp. 119
Author(s):  
Mondher Dhaouadi ◽  
M. Mabrouk ◽  
T. Vuong ◽  
A. Ghazel
Keyword(s):  
Near Field ◽  
Far Field ◽  
Rfid Applications
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