Vibroacoustic Characterization of a New Hybrid Wing-Body Fuselage Concept

2012 ◽  
Author(s):  
Albert Allen ◽  
Adam Przekop
Keyword(s):  
Energy Analysis ◽  
Acoustic Radiation ◽  
Analysis Model ◽  
Energy Correlation ◽  
Model Predictions ◽  
Out Of Plane ◽  
Thin Skin ◽  
Radiated Sound ◽  
Radiated Sound Power

A lighter, more robust airframe design is required to withstand the loading inherent to next generation non–cylindrical commercial airliners. The Pultruded Rod Stitched Efficient Unitized Structure concept, a highly integrated composite design involving a stitched and co-cured substructure, has been developed to meet such requirements. While this structure has been shown to meet the demanding out-of-plane loading requirements of the flat-sided pressurized cabin design, there are concerns that the stiff co-cured details will result in relatively high acoustic radiation efficiencies at frequencies well below the thin skin acoustic coincidence frequency. To address this concern and establish a set of baseline vibroacoustic characteristics, a representative test panel was fabricated and a suite of tests were conducted that involved measurements of panel vibration and radiated sound power during point force and diffuse acoustic field excitations. Experimental results are shown and compared with Finite Element and Statistical Energy Analysis model predictions through the use of modal and energy correlation techniques among others. The behavior of the structure subject to turbulent boundary layer excitation is also numerically examined.

Acoustic Radiation Simulation of Marine Sliding-Thrust Bearing Shell Based on SYSNOISE

2011 ◽  
Vol 291-294 ◽  
pp. 1961-1964
Author(s):  
Guang Liang Zhao
Keyword(s):  
Dynamic Analysis ◽  
Boundary Element ◽  
Thrust Bearing ◽  
Acoustic Radiation ◽  
Element Model ◽  
Sound Power ◽  
Supporting Structure ◽  
Radiated Sound ◽  
The Impact ◽  
Radiated Sound Power

This paper takes marine Kingsbury sliding thrust bearing as the research object and conducts the finite element dynamic analysis with the aid of ANSYS software. On this basis, the acoustic boundary element model of a sliding thrust bearing shell is established with the ANSYS dynamic analysis results as the boundary excitation conditions. Besides, the radiated sound power of the shell is calculated by indirect boundary element method in SYNOSISE software. The influence of different condition parameters on the radiated sound power of the shell is perceived through the analysis of several rotation-thrust conditions. As for the special structure of this kind of sliding-thrust bearing, this paper states the impact of the supporting structure performance parameters, the pad number and damp of shell on the shell radiated sound power. The optimized measure for the supporting structure and the plan concerning the pad number’s selection lays the theoretical basis for damping and noise-reducing research on marine sliding-thrust bearing and its rotor system.

A compact active structural acoustic control method for minimizing radiated sound power

2021 ◽  
Vol 263 (3) ◽  
pp. 3396-3406
Author(s):  
Scott Sommerfeldt
Keyword(s):  
Control Method ◽  
Acoustic Radiation ◽  
Structural Vibration ◽  
Sound Power ◽  
Flat Plates ◽  
Spatial Gradients ◽  
Acoustic Control ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Structural Acoustic Control

Active structural acoustic control is an active control method that controls a vibrating structure in a manner that reduces the sound power radiated from the structure. Such methods focus on attenuating some metric that results in attenuated sound power, while not necessarily minimizing the structural vibration. The work reported here outlines the weighted sum of spatial gradients (WSSG) control metric as a method to attenuate structural radiation. The WSSG method utilizes a compact error sensor that is able to measure the acceleration and the acceleration gradients at the sensor location. These vibration signals are combined into the WSSG metric in a manner that is closely related to the radiated sound power, such that minimizing the WSSG also results in a minimization of the sound power. The connection between WSSG and acoustic radiation modes will be highlighted. Computational and experimental results for both flat plates and cylindrical shells will be presented, indicating that the WSSG method can achieve near optimal attenuation of the radiated sound power with a minimum number of sensors.

Quieting Plate Modes With Optimally Sized Point Masses: A Volume Velocity Approach

1995 ◽  
Author(s):  
Hans-Walter Wodtke ◽  
Gary H. Koopmann
Keyword(s):  
Acoustic Radiation ◽  
Sound Intensity ◽  
Structural Vibration ◽  
Acoustic Response ◽  
Radiation Problem ◽  
Volume Velocity ◽  
Intensity Measurements ◽  
Radiated Sound ◽  
The Masses ◽  
Radiated Sound Power

Abstract The radiated sound power of the second symmetric mode of a clamped square plate is minimized by attaching optimally sized point masses to the plate. The plate is driven by a point force at its center and the positions of the masses are prescribed. The structural vibration problem is solved using a simple Rayleigh-Ritz approach. Solving the acoustic radiation problem is simplified by making a low-ka-assumption, i.e., the point masses are determined so as to minimize the surface volume velocity of the plate. The predicted results are verified experimentally by means of sound intensity measurements. It is shown that a structural resonance can be deleted from the acoustic response by exploiting volume velocity cancellation. The effects involved are illustrated in detail.

ENFORCING RECIPROCITY IN NUMERICAL ANALYSIS OF ACOUSTIC RADIATION MODES AND SOUND POWER EVALUATION

2012 ◽  
Vol 20 (03) ◽  
pp. 1250005 ◽  
Author(s):  
HERWIG PETERS ◽  
NICOLE KESSISSOGLOU ◽  
STEFFEN MARBURG
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Acoustic Radiation ◽  
Sound Power ◽  
Impedance Matrix ◽  
Radiated Sound ◽  
The Asymmetry ◽  
Power Evaluation ◽  
Radiated Sound Power ◽  
Element Method

By identifying the efficiently radiating acoustic radiation modes of a fluid loaded vibrating structure, the storage requirements of the acoustic impedance matrix for calculation of the sound power using the boundary element method can be greatly reduced. In order to compute the acoustic radiation modes, the impedance matrix needs to be symmetric. However, when using the boundary element method, it is often found that the impedance matrix is not symmetric. This paper describes the origin of the asymmetry of the impedance matrix and presents a simple way to generate symmetry. The introduction of additional errors when symmetrizing the impedance matrix must be avoided. An example is used to demonstrate the behavior of the asymmetry and the effect of symmetrization of the impedance matrix on the sound power. The application of the technique presented in this work to compute the radiated sound power of a submerged marine vessel is discussed.

A method to compute the radiated sound power based on mapped acoustic radiation modes

2014 ◽  
Vol 135 (2) ◽  
pp. 679-692 ◽  
Author(s):  
Haijun Wu ◽  
Weikang Jiang ◽  
Yilin Zhang ◽  
Wenbo Lu
Keyword(s):  
Acoustic Radiation ◽  
Sound Power ◽  
Radiated Sound ◽  
Radiated Sound Power

Experimental Characterization of a Car Window Excited by Turbulent Flow Using Scanning Sound Intensity Techniques

2012 ◽  
Author(s):  
Daniel Fernandez Comesaña ◽  
Eduardo Latorre Iglesias ◽  
Malcolm Smith ◽  
Hans-Elias de Bree
Keyword(s):  
Turbulent Flow ◽  
Particle Velocity ◽  
Automotive Industry ◽  
Sound Intensity ◽  
Aerodynamic Noise ◽  
Experimental Characterization ◽  
Velocity Measurements ◽  
Radiated Sound ◽  
Radiated Sound Power

Reducing the aerodynamic noise produced by turbulent flow exciting a car window is one of the current noise control challenges in the automotive industry. Flow separation and later reattachment into a turbulent boundary layer and turbulent wake occur because of flow over the A-pillar and the wing mirror. Experiments have been carried out to represent an idealised wing mirror noise problem using flow over a half cylinder exciting a flat plate. A scanning P-U (pressure-particle velocity) probe was used to measure various aspects of the window response and sound radiation, including the energy distribution of the vibrating surface, the total radiated sound power and hence the radiation efficiency. In addition, experimental results showed that the operational deflection shapes of the car window can be visualized by using scanning particle velocity measurements, obtaining similar results as with step-by-step measurements using a roving accelerometer. The scanning sound intensity maps also proved to be helpful for detecting weaknesses of the initial experimental setup as part of the experimental optimization.

Application of the Helmholtz Integral in Acoustics

1986 ◽  
Vol 108 (4) ◽  
pp. 447-453 ◽  
Author(s):  
M. A. Latcha ◽  
A. Akay
Keyword(s):  
Acoustic Radiation ◽  
Surface Element ◽  
Sound Power ◽  
Acoustic Response ◽  
Element Size ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Helmholtz Integral

The solution of an isoparametric, overdetermined formulation of the Helmholtz Integral is presented and demonstrated in three examples of acoustic radiation from spherical sources. The placement of the interior, overdetermining points is discussed and guidelines concerning surface element size are developed and tested. The total radiated sound power and transient acoustic response of a dilating sphere are computed.

Shaping acoustic radiation induced by vibrotactile rendering on a touch surface

2021 ◽  
Vol 263 (2) ◽  
pp. 4322-4328
Author(s):  
Sangwon Park ◽  
Wheejae Kim ◽  
Dongjoon Kim ◽  
No-Cheol Park
Keyword(s):  
Acoustic Radiation ◽  
Sound Radiation ◽  
Vibrotactile Feedback ◽  
Acrylic Plate ◽  
Vibration Responses ◽  
Radiation Induced ◽  
Measured Frequency Response ◽  
Radiated Sound ◽  
The Relationship ◽  
Radiated Sound Power

Many electronic devices with touch-sensitive surfaces aim to provide vibrotactile feedback, along with visual or auditory feedback, to facilitate the interaction between the user and the interface. In parallel to these efforts, recent studies developed various vibration rendering techniques, enabling more complex vibration patterns to be generated on the touch surface. However, few have addressed sound radiation induced by vibrotactile rendering on a touch surface, which could significantly impact the haptic interaction's overall perception. This study presents a method to shape the acoustic radiation due to rendering high-fidelity vibrotactile feedback on a touch surface. The proposed method utilizes measured frequency response functions and a vibroacoustic representation of the touch surface to define the relationship between actuator driving signals, vibration responses on the touch surface, and radiated sound power. Proper actuator driving signals are derived from the optimization problem formulated using the relationship. The proposed method was demonstrated through vibration rendering experiments on a touch surface comprising an acrylic plate and voice coil actuators. The results showed that the proposed method could shape the acoustic radiation while rendering target vibration patterns at desired positions on the touch surface. This study's proposed method could allow haptic engineers to design vibrotactile feedback and sound radiation simultaneously for a more compelling haptic experience.

EXELFS Studies of Carbon Fibers

1990 ◽  
Vol 48 (2) ◽  
pp. 72-73
Author(s):  
V. Serin ◽  
K. Hssein ◽  
G. Zanchi ◽  
J. Sévely
Keyword(s):  
Carbon Fibers ◽  
Energy Analysis ◽  
Electron Excitation ◽  
Complex Structures ◽  
High Modulus ◽  
Promising Technique ◽  
X Ray ◽  
Fine Structures ◽  
X Ray Absorption

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

Electrical Characterization of InAs/(GaIn)Sb Infrared Superlattice Photodiodes for the 8 to 12νm Range

1999 ◽  
Vol 607 ◽  
Author(s):  
L. Bürkle ◽  
F. Fuchs ◽  
R. Kiefer ◽  
W. Pletschen ◽  
R. E. Sah ◽  
...  
Keyword(s):  
Electrical Characterization ◽  
Cutoff Wavelength ◽  
Saturation Current ◽  
Diffusion Limited ◽  
Saturation Current Density ◽  
Out Of Plane ◽  
Reverse Saturation Current ◽  
The Magnetic Field ◽  
Diode Current

AbstractInAs/(GaIn)Sb superlattice photodiodes with a cutoff wavelength of 8.711μm show adynamic impedance of R0A= 1.5 kωcm2at 77 K and a responsivity of 2 A/W, corresponding to a detectivity of D*= 1 x 1012 cmv√Hz/W. Diffusion limited performance is observed above 100 K. At lower temperatures the diodesare limited by generation-recombination currents. An analysis of the influence of different diode sidewall passivations on the surface contribution to the diode leakage current is presented. The out-of-plane electron mobility as well as the relative contributions of the electron and hole diffusion currents to the diode current were determined by a measurement of the magnetic field dependence of the reverse saturation current density of the diodes

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