Noise Transmission Control Studies on a Chamber Core Composite Cylinder

2002 ◽  
Author(s):  
Deyu Li ◽  
Jeffrey S. Vipperman
Keyword(s):  
Critical Frequency ◽  
Passive Control ◽  
Sound Transmission ◽  
Cavity Resonance ◽  
Beam Model ◽  
Structural Stiffness ◽  
Composite Cylinder ◽  
Transmission Control ◽  
Box Beam ◽  
Acoustic Control

The vibroacoustic behavior and sound transmission properties of a mock-scale chamber core composite cylinder were studied, and the feasibility of the active structural acoustic control and passive control was also investigated. A box-beam model of the chamber core cylindrical shell was used for calculating the critical frequency and the ring frequency. The coupling problems between structural and acoustic modes were investigated, and the structural and acoustic modal parameters were identified from measured data. The sound transmission into the chamber core cylindrical structure was measured with and without fill materials in its wall chambers. The structural stiffness-, cavity resonance-, coincidence-, and mass-controlled zones were identified and verified.

scholarly journals Confinement of Vibrations in Variable-Geometry Nonlinear Flexible Beam

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
W. Gafsi ◽  
F. Najar ◽  
S. Choura ◽  
S. El-Borgi
Keyword(s):  
Passive Control ◽  
Inverse Eigenvalue Problem ◽  
Beam Dynamics ◽  
Mode Shapes ◽  
Physical Parameters ◽  
Geometrical Parameters ◽  
Flexible Beam ◽  
Beam Model ◽  
Nonlinear Frequency ◽  
Nonlinear Beam

In this paper, we propose a novel strategy for controlling a flexible nonlinear beam with the confinement of vibrations. We focus principally on design issues related to the passive control of the beam by proper selection of its geometrical and physical parameters. Due to large deflections within the regions where the vibrations are to be confined, we admit a nonlinear model that describes with precision the beam dynamics. In order to design a set of physical and geometrical parameters of the beam, we first formulate an inverse eigenvalue problem. To this end, we linearize the beam model and determine the linearly assumed modes that guarantee vibration confinement in selected spatial zones and satisfy the boundary conditions of the beam to be controlled. The approximation of the physical and geometrical parameters is based on the orthogonality of the assumed linear mode shapes. To validate the strategy, we input the resulting parameters into the nonlinear integral-partial differential equation that describes the beam dynamics. The nonlinear frequency response curves of the beam are approximated using the differential quadrature method and the finite difference method. We confirm that using the linear model, the strategy of vibration confinement remains valid for the nonlinear beam.

Passive control of deep cavity shear layer flow at subsonic speed

2017 ◽  
Vol 95 (10) ◽  
pp. 894-899
Author(s):  
Mouhammad El Hassan ◽  
Laurent Keirsbulck
Keyword(s):  
Shear Layer ◽  
Passive Control ◽  
Control Method ◽  
Leading Edge ◽  
Layer Growth ◽  
Cavity Resonance ◽  
Passive Flow Control ◽  
Acoustic Coupling ◽  
Deep Cavity ◽  
Layer Flow

Passive control of the flow over a deep cavity at low subsonic velocity is considered in the present paper. The cavity length-to-depth aspect ratio is L/H = 0.2. particle image velocimetry (PIV) measurements characterized the flow over the cavity and show the influence of the control method on the cavity shear layer development. It is found that both the “cylinder” and the “shaped cylinder”, placed upstream from the cavity leading edge, result in the suppression of the aero-acoustic coupling and highly reduce the cavity noise. It should be noted that the vortical structures impinge at almost the same location near the cavity downstream corner with and without passive control. The present study allows to identify an innovative passive flow control method of cavity resonance. Indeed, the use of a “shaped cylinder” presents similar suppression of the cavity resonance as with the “cylinder” but with less impact on the cavity flow. The “shaped cylinder” results in a smaller shear layer growth than the cylinder. Velocity deficiency and turbulence levels are less pronounced using the “shaped cylinder”. The “cylinder” tends to diffuse the vorticity in the cavity shear layer and thus the location of the maximum vorticity is more affected as compared to the “shaped cylinder” control. The fact that the “shaped cylinder” is capable of suppressing the cavity resonance, despite the vortex shedding and the high frequency forcing being suppressed, is of high interest from fundamental and applied points of view.

The System for Active Control of Sound Transmission through a Window Panel – The Concept and Simulation Results

2016 ◽  
Vol 248 ◽  
pp. 35-40
Author(s):  
Leszek Morzyński ◽  
Wiktor Marek Zawieska ◽  
Tomasz Krukowicz
Keyword(s):  
Feedforward Control ◽  
Reference Signal ◽  
Sound Transmission ◽  
Wide Band ◽  
High Amplitude ◽  
Convergence Time ◽  
Signal Spectrum ◽  
Sound Insulation ◽  
Common Mean ◽  
Acoustic Control

High acoustic insulation windows are common mean to decrease sound transmission to closed spaces. Hence, the improvement of sound insulation of windows is very important research issue. In this paper partial results of research project aimed at synthesis of the window panel with actively controlled sound transmission are presented. Recent stage of the project is focused on the development of multichannel Active Structural Acoustic Control algorithm. High amplitude excitation produces nonlinear vibration effects. Using feedforward control strategy it is convenient to control not only the reference signal spectrum, but also additional frequencies generated as the cause of nonlinearity. Therefore neural network based algorithm is considered. To lower the computational burden of the algorithm, round robin based error backpropagation learning is employed. The results of numerical simulations are presented. Major conclusion of presented part of the research is that the algorithm is capable of controlling a wide-band noise efficiently. Reduction of the computational complexity leads to increased convergence time, not influencing the final value of mean square error.

701 Acoustic enclosure with active sound transmission control

2010 ◽  
Vol 2010 (0) ◽  
pp. _701-1_-_701-5_
Author(s):  
Akira SANADA ◽  
Kouji HIGASHIYAMA ◽  
Nobuo TANAKA
Keyword(s):  
Sound Transmission ◽  
Transmission Control

Active structural acoustic control of broadband sound transmission through a panel

1996 ◽  
Author(s):  
D. Peterson ◽  
G. Toth ◽  
B. Tran ◽  
G. Mathur ◽  
M. Simpson
Keyword(s):  
Sound Transmission ◽  
Acoustic Control ◽  
Broadband Sound ◽  
Structural Acoustic Control
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