Auditory Evaluation of Sounds Radiated from a Vibrating Plate Inside a Damped Cavity (original) (raw)

Incorporating damping predictions in the vibroacoustic design process

2004

Controlling vibration amplification phenomena is a critical aspect of structural dynamics. Innovative devices, such as SPADD R are now available, that allow much better damping performance than classical free and constrained layer treatments. The current practice in vibration design does not however incorporate damping modeling so that a new range of tools is needed. The paper first presents functional models of SPADD R devices and discusses applicable placement strategies. In a second part, one analyzes optimization strategies that can be considered in the design of damping treatments. First one presents the necessary trade-off between rapid estimates, needed in a phase where the damping potential is to be evaluated, and more costly estimates, needed in design refinement. It shown that very appropriate trends can be obtained using fast approximations implemented in the ProSPADD software package. The need to define appropriate objective functions is then discussed. Illustrations are given using the simplified model of a body in white with two treatments targeting the first torsion and a panel mode respectively.

Prediction of Vibro-Acoustic Response of Enclosed Spaces by Using Structural Modification Techniques

Low frequency noise caused by vibrating panels can become a problem for vehicles from NVH standpoint. The vibro-acoustic analysis of a simplified vehicle model is presented in this study. Analysis of vibro-acoustic behavior includes frequency response analysis of structure by Finite Element Method (FEM) and sound pressure level (SPL) prediction of the cabin interior by Boundary Element Method (BEM). The structural design of the vibrating panels can be modified by adding stiffeners to improve the acoustic field inside the cabin. The dynamic analysis of the structural model must be repeated after every modification which will be a time consuming process in the design stage. In this study, a methodology that utilizes the frequency response functions (FRFs) of the original model for the reanalysis of the structure that is subjected to structural modification is adapted. Modal analysis of the original structure is performed only once to obtain the receptance values. Then, the structural modification method is used to calculate the receptances of the modified system. The structural modification method uses the receptances of the original system and the dynamic stiffness matrix of the modifying part of the structure. The response of the structure obtained from receptances of the modified structure is then used to supply vibration data as boundary condition for acoustic analysis of the cavity for SPL prediction at desired points.

Global sensitivity analysis of analytical vibroacoustic transmission models

Journal of Sound and Vibration, 2016

Noise reduction issues arise in many engineering problems. One typical vibroacoustic problem is the transmission loss (TL) optimisation and control. The TL depends mainly on the mechanical parameters of the considered media. At early stages of the design, such parameters are not well known. Decision making tools are therefore needed to tackle this issue. In this paper, we consider the use of the Fourier Amplitude Sensitivity Test (FAST) for the analysis of the impact of mechanical parameters on features of interest. FAST is implemented with several structural configurations. FAST method is used to estimate the relative influence of the model parameters while assuming some uncertainty or variability on their values. The method offers a way to synthesize the results of a multiparametric analysis with large variability. Results are presented for transmission loss of isotropic, orthotropic and sandwich plates excited by a diffuse field on one side. Qualitative trends found agree with the physical expectation. Design rules can then be set up

Use of genetic algorithms for the vibroacoustic optimization of plates

The Journal of the Acoustical Society of America, 1997

Optimal design of mechanical structures for vibration or noise reduction often requires finding the minima of highly nonlinear multi-dimensional functions. In this paper, genetic algorithms are introduced as a new promising tool for numerical optimization of such problems. The application presented is on the control of the vibroacoustic response of a plate carrying point-masses. Genetic algorithms have been used to determine the optimal positions of the masses on the plate. Several cases are presented, using various optimization criteria, showing the importance of selecting the most appropriate criterion.

Un Modele Vibroacoustique Pour Prevoir L'Effet De Niche Sur La Perte Par Transmission Sonore

2013

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Derivation of experimental vibro-acoustical models for ANC configuration design

3rd AIAA/CEAS Aeroacoustics Conference, 1997

In the context of the European cooperative research project ASANCA II, methods for active control of aircraft interior noise using acoustical as well as structural excitation are investigated. One of the main tasks of the project consists of researching methods for deriving a global vibro-acoustical model of the aircraft fuselage-cabin cavity system in the frequency range corresponding to the first blade pass frequencies. Hereto, an extensive experimental study was performed on an aircraft test section. A full frequency response function matrix was measured between a large number of structural and acoustical degrees of freedom. Based on these test data, both parametric (structural, acoustical and vibro-acoustical) modal models as well as non-parametric (vibroacoustical principal field shape) system models were identified to gain insight in the dominating physical phenomena in the concerned frequency range. Furthermore, the data set was used as the basis for designing and optimal control configuration. Combined with a typical primary field, the vibroacoustic system description allows to generate a prediction of the active noise and vibration control performance as a function of the number of actuators used.

Use of genetic algorithms for the vibroacoustic optimization of a plate carrying point-masses

Journal of the Acoustical Society of America, 1998

Optimal design of mechanical structures for vibration or noise reduction often requires finding the minima of highly nonlinear multi-dimensional functions. In this paper, genetic algorithms are introduced as a new promising tool for numerical optimization of such problems. The application presented is on the control of the vibroacoustic response of a plate carrying point-masses. Genetic algorithms have been used to determine the optimal positions of the masses on the plate. Several cases are presented, using various optimization criteria, showing the importance of selecting the most appropriate criterion.

Filter Banks Implementation of Numerical Models for Vibroacoustic Analysis in the Medium Frequency Range

Journal of Sound and Vibration, 1998

A numerical method is proposed for predicting the vibroacoustic response of a viscoelastic structure submitted to harmonic forces in the medium frequency range. The structure is described as a finite dimension dynamical system. The frequency domain of interest is divided into several different subdomains. The method consists of solving a set of time domain equations of motion where each of them is associated with a given frequency subdomain. This time-frequency study is formulated within the framework of non-uniform modulated filter banks. Conditions are given to ensure that the analysis and the synthesis banks allow reconstruction of the complete investigated displacement field from the time solutions. A low-pass filter with a compact time support is designed to ensure an efficient computation. To illustrate the discussion, two examples using different variational approaches are proposed. First, flexural vibrations of an in vacuo steel plate described by a finite element method is considered. Second, a semi-analytical method is used to describe a point loaded steel plate radiating in air.