Reconstructing acoustic field based on the normal surface velocity input data

2015 ◽  
Vol 137 (4) ◽  
pp. 2234-2234
Author(s):  
wu zhu ◽  
Sean F. Wu
Keyword(s):  
Acoustic Field ◽  
Input Data ◽  
Surface Velocity ◽  
Normal Surface ◽  
Velocity Input

Modeling Vibration-Induced Tire-Pavement Interaction Noise in the Mid-frequency Range

2020 ◽  
Author(s):  
Sterling McBride ◽  
Ricardo Burdisso ◽  
Corina Sandu
Keyword(s):  
Sound Intensity ◽  
Element Model ◽  
Dominant Frequency ◽  
Contact Forces ◽  
Surface Velocity ◽  
New Wave ◽  
Normal Surface ◽  
Radiated Noise ◽  
Physical Effects ◽  
Effects Of Rotation

ABSTRACT Tire-pavement interaction noise (TPIN) is one of the main sources of exterior noise produced by vehicles traveling at greater than 50 kph. The dominant frequency content is typically within 500–1500 Hz. Structural tire vibrations are among the principal TPIN mechanisms. In this work, the structure of the tire is modeled and a new wave propagation solution to find its response is proposed. Multiple physical effects are accounted for in the formulation. In an effort to analyze the effects of curvature, a flat plate and a cylindrical shell model are presented. Orthotropic and nonuniform structural properties along the tire's transversal direction are included to account for differences between its sidewalls and belt. Finally, the effects of rotation and inflation pressure are also included in the formulation. Modeled frequency response functions are analyzed and validated. In addition, a new frequency-domain formulation is presented for the computation of input tread pattern contact forces. Finally, the rolling tire's normal surface velocity response is coupled with a boundary element model to demonstrate the radiated noise at the leading and trailing edge locations. These results are then compared with experimental data measured with an on-board sound intensity system.

An investigation into the relationship between sound intensity and normal surface velocity

2007 ◽  
Vol 121 (5) ◽  
pp. 3155-3155
Author(s):  
Mark Boyle ◽  
Matthew Cassidy ◽  
Richard Cooper ◽  
Richard Gault ◽  
Jian Wang
Keyword(s):  
Sound Intensity ◽  
Surface Velocity ◽  
Normal Surface ◽  
The Relationship

Topology Optimization of Passive Constrained Layer Damping on Plates with Respect to Noise Control

2013 ◽  
Vol 774-776 ◽  
pp. 3-6
Author(s):  
Ying Feng Lei ◽  
Wei Guang Zheng ◽  
Qi Bai Huang ◽  
Chuan Bing Li
Keyword(s):  
Topology Optimization ◽  
Numerical Study ◽  
Harmonic Excitation ◽  
Surface Velocity ◽  
Viscoelastic Layer ◽  
Constrained Layer Damping ◽  
Objective Functions ◽  
Normal Surface ◽  
Simple Interface ◽  
Passive Constrained Layer Damping

The square of normal surface velocity of a thin plate with a harmonic excitation is minimized by optimizing the topologies of attached passive constrained layer damping (PCLD) treatments. An extended solid isotropic material with penalization model for topology optimization is introduced based on a simple interface finite element modeling for viscoelastic layer of PCLD patch. For the purpose of illustrating the proposed method, a clamped square plate is used in the numerical study. Significant reductions of the objective functions are achieved by the optimal distributions.

COMPUTATION OF ACOUSTIC FIELD RADIATED BY A SPHERICAL SOURCE NEAR A THERMOVISCOUS FLUID SPHERE

2007 ◽  
Vol 15 (02) ◽  
pp. 159-180
Author(s):  
S. M. HASHEMINEJAD ◽  
A. H. PASDAR
Keyword(s):  
Acoustic Field ◽  
Acoustic Radiation ◽  
Conducting Fluid ◽  
Surface Velocity ◽  
Fluid Sphere ◽  
Spherical Source ◽  
Fluid Medium ◽  
Multiple Precision ◽  
Thermally Conducting ◽  
Thermoviscous Fluid

Acoustic radiation from a spherical source, vibrating with an arbitrary, axisymmetric, time-harmonic surface velocity distribution, while immersed near a thermoviscous fluid sphere suspended in an unbounded viscous thermally conducting fluid medium is computed. The formulation utilizes the appropriate wave field expansions and boundary conditions along with the translational addition theorem for spherical wave functions to develop a closed-form solution in form of infinite series. The prime objective is to investigate the thermoviscous loss effects on acoustic radiation and its associated field quantities. The analytical results are illustrated with a numerical example in which the spherical source, that may vibrate either in a monopole-like or a dipole-like mode, is suspended in a thermoviscous fluid medium near an equal-sized viscous thermally conducting fluid sphere. To avoid numerical difficulties normally arising in process of solving thermoviscous radiation/scattering problems in the frequency range of interest, a basic multiple precision FORTRAN computation package was utilized in developing specialized codes for computing special mathematical functions including spherical Bessel functions of complex argument and performing large complex matrix manipulations on floating point numbers of arbitrarily high precision. The essential acoustic field quantities such as the modal acoustic radiation impedance load on the source, the radiated far-field pressure directivity pattern and the radiated on-axis pressure are evaluated and discussed for representative values of the parameters characterizing the system. Limiting cases are examined and excellent agreements with well known solutions are attained.

A Modified Helmholtz Equation Least Squares Method for Reconstructing Vibroacoustic Quantities on an Arbitrarily Shaped Vibrating Structure

2021 ◽  
pp. 2150006
Author(s):  
Lingguang Chen ◽  
Sean F. Wu
Keyword(s):  
Helmholtz Equation ◽  
Numerical Simulations ◽  
Least Square ◽  
Surface Velocity ◽  
Source Surface ◽  
Target Structure ◽  
Normal Surface ◽  
Reconstruction Process ◽  
Modified Helmholtz Equation ◽  
Accurate Reconstruction

A modified Helmholtz equation least-square (HELS) method is developed to reconstruct vibroacoustic quantities on an arbitrarily shaped vibrating structure. Unlike the traditional nearfield acoustical holography that relies on the acoustic pressures collected on a hologram surface at a short stand-off distance to a target structure, this modified HELS method takes the partial normal surface velocities and partial acoustic pressures as the input data. The advantages of this approach include but not limited to: (1) The normal surface velocities that represent the nearfield effects are collected directly, which lead to a more accurate reconstruction of the normal surface velocity distribution; (2) The field acoustic pressures are also measured, which leads to a more accurate reconstruction of the acoustic pressure on the source surface as well as in the field; and (3) There is no need to measure the normal surface velocities over the entire surface, which makes this approach quite appealing in practice because most vibrating structures do not allow for measuring the normal surface velocities over the entire source surface as there are always obstacles or constrains around a target structure. Needless to say, regularization is necessary in reconstruction process since all inverse problems are mathematically ill-posed. To validate this approach, both numerical simulations and experimental results are presented. An optimal reconstruction scheme is developed via numerical simulations to achieve the most cost-effective reconstruction results for practical applications.

Laser Tools for Diesel Engine Diagnosis

1985 ◽  
Vol 199 (4) ◽  
pp. 295-300 ◽  
Author(s):  
P G Eastwood ◽  
N A Halliwell ◽  
P Gilbert
Keyword(s):  
Standard Technique ◽  
Target Surface ◽  
Arbitrary Cross Section ◽  
Surface Velocity ◽  
Vibration Velocity ◽  
Normal Surface ◽  
Time Resolved ◽  
Fuel Injectors ◽  
Contact Measurement ◽  
New Instrument

Two portable laser instruments are described which allow the engineer to simply ‘stand and point’ laser beams at a target surface in order to obtain a measurement of time-resolved vibration velocity. The first supplements the accelerometer and measures normal surface velocity but offers the advantage of non-contact measurement. Its use is demonstrated in detecting reduced nozzle pressures in fuel injectors. The second instrument is a laser torsional vibrometer which measures torsional oscillations of rotating machinery parts and in particular crankshaft oscillation. Comparisons are made with the more standard technique which utilizes a slotted disc. The new instrument provides advantages of non-contact measurement, insensitivity to shaft radial motion and the ability to measure oscillations of shafts of arbitrary cross-section.

Determination of Vibrating Structure Patterns Using Acoustic Waves

2008 ◽  
Author(s):  
P. A. Lewin ◽  
W. A. Berger ◽  
C. J. Vecchio ◽  
M. E. Schafer
Keyword(s):  
Acoustic Field ◽  
Acoustic Waves ◽  
Angular Spectrum ◽  
Field Analysis ◽  
Surface Velocity ◽  
Design And Optimization ◽  
Reconstructed Surface ◽  
Ultrasound Applications ◽  
Structure Patterns

The objective of this work was to develop an acoustic field based technique that would be capable of remote sensing and reproduction of vibrating structure patterns. Knowledge of vibrating pattern characteristics is of interest in many applications, including minimization of noise generation in different media and design and optimization of piezoelectric transducers used in diagnostic ultrasound imaging. The technique is based on the angular spectrum method of wave-field analysis, and is applicable to both continuous and wideband pulsed waves. It also allows the effects of acoustic parameters such as absorption, dispersion, refraction, and phase distortion to be accounted for. Examples of remotely reconstructed surface velocity distributions of complex acoustic radiators operating in the low MHz (1–3MHz) range of frequencies will be presented. The examined geometries include single focused and plane axi-symmetric sources and arrays similar to those employed in both diagnostic and therapeutic ultrasound applications. The initial results obtained demonstrate the applicability of the angular spectrum approach and its extension to the analysis of acoustic field propagation through nonlinear liquid media. The method holds particular promise for use as a tool in the design and optimization of acoustic radiators. The ultimate goal of this research is to develop the model useful in optimization of ultrasound transducer performance and providing information on the degradation of transducer performance due to propagation through complex nonlinear media such as biological tissue.

Transmission Electron Diffraction Analysis by Computer

1970 ◽  
Vol 28 ◽  
pp. 40-41
Author(s):  
R.A. Ploc ◽  
G.H. Keech
Keyword(s):  
Electron Diffraction ◽  
Input Data ◽  
Reciprocal Lattice ◽  
Computer Programme ◽  
Transmission Electron Diffraction ◽  
Usual Procedure ◽  
Transmission Electron ◽  
Complex Shapes ◽  
Computer Input ◽  
Diffraction Effects

An unambiguous analysis of transmission electron diffraction effects requires two samplings of the reciprocal lattice (RL). However, extracting definitive information from the patterns is difficult even for a general orthorhombic case. The usual procedure has been to deduce the approximate variables controlling the formation of the patterns from qualitative observations. Our present purpose is to illustrate two applications of a computer programme written for the analysis of transmission, selected area diffraction (SAD) patterns; the studies of RL spot shapes and epitaxy.When a specimen contains fine structure the RL spots become complex shapes with extensions in one or more directions. If the number and directions of these extensions can be estimated from an SAD pattern the exact spot shape can be determined by a series of refinements of the computer input data.

The Effect of Benzene on Bluegill Olfactory Lamellae

1985 ◽  
Vol 43 ◽  
pp. 574-575
Author(s):  
D.R. Mattie ◽  
J.W. Fisher
Keyword(s):  
Surface Morphology ◽  
Soluble Fraction ◽  
Lepomis Macrochirus ◽  
Sublethal Concentration ◽  
Water Soluble ◽  
Major Constituent ◽  
Jet Fuels ◽  
Aquatic Biota ◽  
Normal Surface ◽  
Cacodylate Buffer

Jet fuels such as JP-4 can be introduced into the environment and come in contact with aquatic biota in several ways. Studies in this laboratory have demonstrated JP-4 toxicity to fish. Benzene is the major constituent of the water soluble fraction of JP-4. The normal surface morphology of bluegill olfactory lamellae was examined in conjunction with electrophysiology experiments. There was no information regarding the ultrastructural and physiological responses of the olfactory epithelium of bluegills to acute benzene exposure.The purpose of this investigation was to determine the effects of benzene on the surface morphology of the nasal rosettes of the bluegill sunfish (Lepomis macrochirus). Bluegills were exposed to a sublethal concentration of 7.7±0.2ppm (+S.E.M.) benzene for five, ten or fourteen days. Nasal rosettes were fixed in 2.5% glutaraldehyde and 2.0% paraformaldehyde in 0.1M cacodylate buffer (pH 7.4) containing 1.25mM calcium chloride. Specimens were processed for scanning electron microscopy.

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