Experimental validation of a method for the prediction of the acoustic field produced by an acoustic source and the reflected field produced by a solid interface

2012 ◽  
Author(s):  
Sandra Diaz ◽  
Rajiv Chopra ◽  
Samuel Pichardo
Keyword(s):  
Acoustic Field ◽  
Experimental Validation ◽  
Acoustic Source ◽  
Solid Interface

A semianalytical approach to calculate the reflected wave of an eccentric source in a borehole

Geophysics ◽  
2019 ◽  
Vol 84 (1) ◽  
pp. D1-D9
Author(s):  
Feilong Xu ◽  
Hengshan Hu
Keyword(s):  
Acoustic Field ◽  
Fourier Transforms ◽  
Acoustic Source ◽  
Reflection And Transmission ◽  
Reflected Wave ◽  
Reflection And Transmission Coefficient ◽  
Simulation Error ◽  
Pass Through ◽  
Coefficient Method ◽  
Cased Borehole

The acoustic field in a borehole is usually simulated under axisymmetric conditions. When the acoustic source deviates from the borehole axis, the field loses the axial symmetry property. We have developed a semianalytical approach to calculate the acoustic field excited by an eccentric source of limited size. The eccentric source is first decomposed into infinitely long multipole cylinder sources whose center axes pass through the eccentric point. Then, by applying the continuity of displacement and stress on the interfaces, we derive reflection coefficients by the generalized reflection and transmission coefficient method. Finally, the reflected wave is obtained after dual inverse Fourier transforms with respect to time and wavenumber. Numerical tests based on the reciprocity theorem are performed to validate this approach. The results indicate that the simulation error in every reciprocal model is negligible even if the eccentric distance of the acoustic source reaches two thirds of the radius of the borehole wall. We apply this semianalytical approach to simulate the reflected wave of an eccentric directional beam in a cased borehole.

scholarly journals A Numerical Study on the Distribution and Evolution Characteristics of an Acoustic Field in the Time Domain of a Centrifugal Pump Based on Powell Vortex Sound Theory

2019 ◽  
Vol 9 (23) ◽  
pp. 5018 ◽  
Author(s):  
Chang Guo ◽  
Jingying Wang ◽  
Ming Gao
Keyword(s):  
Centrifugal Pump ◽  
Acoustic Field ◽  
Time Domain ◽  
Acoustic Pressure ◽  
Numerical Study ◽  
Source Region ◽  
Centrifugal Pumps ◽  
Acoustic Source ◽  
Evolution Characteristics ◽  
Source Component

The acoustic field distribution and evolution characteristics in a time domain inside a centrifugal pump are studied. During the fluid motion process, the acoustic source and acoustic pressure are basically less than 0, and the minimum value of the two parameters is distributed near the tongue. Additionally, the concentration, break, extend, migration and reaggregation phenomena of the minimum acoustic source region exist. Specifically, as the blade passes through the tongue, the minimum acoustic source region concentrates on the tongue firstly, then extends and migrates downstream slightly with the blade motion, and aggregates again around the tongue, which results in the similar evolution characteristics of acoustic pressure. Moreover, the standard deviation (STD) of acoustic source mainly focuses near the pressure side of blade tail and volute tongue, and the maximum STD is located at the tongue. Compared with the source component induced by stretching of the vortex, the source component induced by non-uniformity of fluid kinetic energy is closer to the overall acoustic source. Take the tongue as an example, at various rotational speeds, the STD proportions of the two components are about 5% and 95%, respectively. This study discusses the generation, distribution and evolution characteristics of acoustic field, which lays a foundation to analyze the acoustic field propagation mechanism of centrifugal pumps.

Reconstruction and Separation in a Semi-Free Field by Using the Distributed Source Boundary Point Method-Based Nearfield Acoustic Holography

2007 ◽  
Vol 129 (3) ◽  
pp. 323-329 ◽  
Author(s):  
C. X. Bi ◽  
X. Z. Chen ◽  
R. Zhou ◽  
J. Chen
Keyword(s):  
Acoustic Field ◽  
Boundary Point ◽  
Free Field ◽  
Treatment Method ◽  
Point Method ◽  
Acoustic Source ◽  
Acoustic Holography ◽  
Distributed Source ◽  
Boundary Point Method ◽  
Nearfield Acoustic Holography

In a semi-free field, the acoustic field is composed of two components: the direct sound and the reflected sound. Because it is difficult to separate the direct sound from the acoustic field, conventional nearfield acoustic holography (NAH) methods cannot reconstruct an acoustic source and predict the acoustic field directly. Through utilization of the distributed source boundary point method (DSBPM)-based NAH, a treatment method for a semi-free field is proposed. In the method, the source in a semi-free field can be reconstructed correctly, and the acoustic field can be predicted and separated. An experiment on a speaker in a semi-anechoic chamber is carried out to verify the proposed method. By comparing the reconstructed and predicted results in DSBPM-based NAH with and without the proposed method, the proposed method is validated. The disadvantages of NAH without any treatment method in a semi-free field are demonstrated.

scholarly journals Plane-wave diffraction by a rational wedge

1987 ◽  
Vol 411 (1841) ◽  
pp. 265-283 ◽  
Keyword(s):  
Plane Wave ◽  
Half Plane ◽  
Acoustic Field ◽  
Angular Variable ◽  
Acoustic Source ◽  
Wave Source ◽  
Easy Calculation ◽  
Special Cases ◽  
Rational Multiple ◽  
Plane Wave Diffraction

In this paper, new expressions for the acoustic field produced when a plane-wave source of sound is diffracted by a soft, hard or mixed soft-hard wedge whose angle can be expressed as a rational multiple of π are given. The solution is expressed in terms of geometrical acoustic source terms and real integrals that represent the diffracted field. The expressions are in a form that allows easy calculation of the acoustic field. Uniformly valid expressions for the far field are also given for all values of the angular variable. The general result obtained includes, as special cases, Sommerfeld’s solution for diffraction by a half-plane, Reiche’s result for the diffraction by a right-angled wedge, and a new representation for the solution of the problem of diffraction by a mixed soft-hard half-plane.

scholarly journals Acoustic scattering by a finite rigid plate with a poroelastic extension

2016 ◽  
Vol 791 ◽  
pp. 414-438 ◽  
Author(s):  
Lorna J. Ayton
Keyword(s):  
Noise Reduction ◽  
Acoustic Field ◽  
Wind Turbines ◽  
Acoustic Scattering ◽  
Leading Edge ◽  
Chord Length ◽  
Far Field ◽  
Rigid Plate ◽  
Acoustic Source ◽  
Trailing Edge

The scattering of sound by a finite rigid plate with a finite poroelastic extension interacting with an unsteady acoustic source is investigated to determine the effects of porosity, elasticity and the length of the extension when compared to a purely rigid plate. The problem is solved using the Wiener–Hopf technique, and an approximate Wiener–Hopf factorisation process is implemented to yield reliable far-field results quickly. Importantly, finite chord-length effects are taken into account, principally the interaction of a rigid leading-edge acoustic field with a poroelastic trailing-edge acoustic field. The model presented discusses how the poroelastic trailing-edge property of owls’ wings could inspire quieter aeroacoustic designs in bladed systems such as wind turbines, and provides a framework for analysing the potential noise reduction of these designs.

scholarly journals Broadband Sound Intensity Interference Frequency Periodicity and Pulse Source Localization

2021 ◽  
Vol 9 (2) ◽  
pp. 200
Author(s):  
Shizhao Zhang ◽  
Shengchun Piao
Keyword(s):  
Acoustic Field ◽  
Sound Intensity ◽  
Pulse Signal ◽  
Doa Estimation ◽  
Estimation Accuracy ◽  
Far Field ◽  
Acoustic Source ◽  
Interference Frequency ◽  
Marine Engineering ◽  
Spatial Interference

In order to analyze the frequency periodicity characteristics of acoustic field interference and realize acoustic source ranging (ASR), the normal mode model is used to analyze the interference characteristics of the broadband acoustic field under the condition of horizontally layered medium; the broadband received signal field when the broadband pulse signal passes through the acoustic field is also simulated. The variation of interference patterns with frequency is analyzed, and their spatial interference characteristics and mechanisms are analyzed. Based on the interference theory, the relation between the acoustic source range and the frequency periodicity of the broadband acoustic intensity interference is derived. Simulation and experimental results show that this relation can accurately estimate the far-field acoustic source range, and the estimation accuracy and real-time performance are greatly improved compared with previous methods. Besides, simulation shows that the method combined with multiple-receiver ranging obtains high-precision direction of arrival (DOA) estimation as well as ASR. The relation between acoustic source position and broadband acoustic field interference frequency periodicity can be used to improve far-field ASR and DOA estimation, which is of great value for oceanography, marine engineering, and marine military. In addition, this relation can also be extended to that between the modal interference frequency periodicity and other related parameters in other physical fields for parameter inversion.

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