Reduction of Hull-Radiated Noise Using Vibroacoustic Optimization of the Propulsion System

2011 ◽  
Vol 55 (03) ◽  
pp. 149-192 ◽  
Author(s):  
Mauro Caresta ◽  
Nicole J. Kessissoglou
Keyword(s):  
Sound Pressure ◽  
Search Algorithm ◽  
Great Influence ◽  
Low Frequency ◽  
Pattern Search ◽  
Propulsion System ◽  
Stiffened Cylindrical Shell ◽  
Radiated Noise ◽  
End Plate ◽  
Radiated Sound

Vibration modes of a submarine are excited by fluctuating forces generated at the propeller and transmitted to the hull via the propeller-shafting system. The low frequency vibrational modes of the hull can result in significant sound radiation. This work investigates reduction of the far-field radiated sound pressure from a submarine using a resonance changer implemented in the propulsion system as well as design modifications to the propeller-shafting system attachment to the hull. The submarine hull is modeled as a fluid-loaded ring-stiffened cylindrical shell with truncated conical end caps. The propeller-shafting system is modeled in a modular approach using a combination of mass-spring-damper elements, beams, and shells. The stern end plate of the hull, to which the foundation of the propeller-shafting system is attached, is modeled as a circular plate coupled to an annular plate. The connection radius of the foundation to the stern end plate is shown to have a great influence on the structural and acoustic responses and is optimized in a given frequency range to reduce the radiated noise. Optimum connection radii for a range of cost functions based on the maximum radiated sound pressure are obtained for both simple support and clamped attachments of the foundation to the hull stern end plate. A hydraulic vibration attenuation device known as a resonance changer is implemented in the dynamic model of the propeller-shafting system. A combined genetic and pattern search algorithm was used to find the optimum virtual mass, stiffness, and damping parameters of the resonance changer. The use of a resonance changer in conjunction with an optimized connection radius is shown to give a significant reduction in the low frequency structure-borne radiated sound.

DEVELOPMENT OF COUPLED FE/BE MODELS TO INVESTIGATE THE STRUCTURAL AND ACOUSTIC RESPONSES OF A SUBMERGED VESSEL

2007 ◽  
Vol 15 (01) ◽  
pp. 23-47 ◽  
Author(s):  
SASCHA MERZ ◽  
SEBASTIAN OBERST ◽  
PAUL G. DYLEJKO ◽  
NICOLE J. KESSISSOGLOU ◽  
YAN K. TSO ◽  
...  
Keyword(s):  
Computational Models ◽  
Sound Pressure ◽  
Low Frequency ◽  
Element Model ◽  
Radial Motion ◽  
Neutral Buoyancy ◽  
Stiffened Cylindrical Shell ◽  
Breathing Motion ◽  
Radiated Sound ◽  
High Level

An analytical model and a fully coupled finite element/boundary element model are developed for a simplified physical model of a submarine. The submerged body is modeled as a ring-stiffened cylindrical shell with finite rigid end closures, separated by bulkheads into a number of compartments and under axial excitation from the propeller-shafting system. Lumped masses are located at each end to maintain a condition of neutral buoyancy. Excitation of the hull axial modes from the propeller-shafting system causes both axial motion of the end closures and radial motion of the shell, resulting in a high level of radiated noise. In the low frequency range, only the axial modes in breathing motion are examined, which gives rise to an axisymmetric case, since these modes are efficient radiators. An expression for the structurally radiated sound pressure contributed by axial movement of the end plates and radial motion of the shell was obtained using the Helmholtz integral equation. In the computational model, the effects of the various influencing factors (ring stiffeners, bulkheads, realistic end closures, and fluid loading) on the free vibrational characteristics of the thin walled cylinder are examined. For both the analytical and computational models, the frequency responses, axial and radial responses of the cylinder, and the radiated sound pressure are compared.

Reduction of the Sound Pressure Radiated by a Submarine by Isolation of the End Caps

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Mauro Caresta ◽  
Nicole J. Kessissoglou
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
Axial Direction ◽  
Radial Component ◽  
Axial Motion ◽  
Low Frequencies ◽  
End Caps ◽  
Passive Isolation ◽  
Radiated Sound ◽  
Finite Cylindrical Shell

A passive isolation approach to reduce the sound pressure radiated by a submarine is presented. The submerged vessel is modeled as a stiffened cylindrical hull partitioned by bulkheads and with two end caps of conical shape. Fluctuating forces from the propeller are transmitted to the hull through the shaft and a rigid foundation, resulting in axisymmetric excitation of the hull. The hull surface motion is mainly in the axial direction with a small radial component due to the coupling between the two orthogonal shell displacements. The sound pressure resulting from the axial motion is radiated from the end caps of the submarine. This work investigates reduction of the far field sound pressure by passive isolation of the end caps from the main hull. Isolation of the axial motion of the end caps from the cylindrical hull results in significant reduction of the radiated sound at low frequencies. The fluid loading approximation for a finite cylindrical shell in the low frequency range is also discussed.

Finite Element Simulation of an Automotive Brake Rotor With Metallic Damping Inserts

2010 ◽  
Author(s):  
Shung H. Sung ◽  
M. David Hanna ◽  
James G. Schroth
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Sound Pressure ◽  
Radiated Noise ◽  
Press Fit ◽  
Modal Damping ◽  
Brake Rotor ◽  
Radiated Sound ◽  
Automotive Brake ◽  
Element Method

A finite element method is developed for simulating the performance of an automotive brake rotor with metallic inserts that are used to dampen the vibration and radiated noise response. The metallic inserts are located in slots that are cast at the edge of the rotor circumference between the two rotor surfaces. Three different rotor configurations are evaluated: (a) an undamped solid rotor, (b) a damped rotor with an unconstrained press-fit metallic insert, and (c) a damped rotor with a constrained cast-in coated metallic insert. Comparisons of the predicted versus measured rotor surface vibration and radiated sound pressure are made to evaluate the effect of the insert and the accuracy of the finite element method. The comparisons show that significant modal damping of the rotor vibration and radiated noise can be achieved through the use of the coated metallic insert. A methodology is developed and applied to evaluate the damping of different metallic inserts and coatings from only the radiated sound pressure response.

CAE Technology Applied to Range Hood’s Noise Control and Optimization Design

2011 ◽  
Vol 338 ◽  
pp. 543-546
Author(s):  
Hu Yu ◽  
Hong Hou ◽  
Liang Sun
Keyword(s):  
Sound Pressure Level ◽  
Optimization Design ◽  
Sound Pressure ◽  
Element Model ◽  
Pressure Level ◽  
Sound Power ◽  
Radiated Noise ◽  
Radiated Sound ◽  
Cae Technology ◽  
Radiated Sound Power

In this study we use the CAE technology to compute and reduce the radiated noise of range hood. First, a finite element model of a typical range hood is created using Hypermesh. Then, the surface particle velocity is carried out in Nastran, and the radiated noise is calculated by Sysnoise. Finally, the DOE-based structural optimization is preformed using iSIGHT-FD, in which the sound pressure level at four sensitive points and the radiated sound power are selected as the objective function and the thickness of four panels are adopted as design variable. In addition, the weight of the range hood as a constraint is kept no more than its original weight. As a result, a maximum radiated sound power reduction of 3.66W and a maximum sound pressure level reduction of 4.7 dB are successfully achieved. It shows the CAE technology is a very efficient and effective method for reducing radiated noise.

Comparative Study on Radiated Noise Estimation Error with Sound Pressure and the Pressure Variation

2011 ◽  
Vol 322 ◽  
pp. 243-247
Author(s):  
Lin Ke Zhang ◽  
Lin He ◽  
Ding Ding Lu ◽  
Jian Cheng Tao
Keyword(s):  
Sound Pressure ◽  
Estimation Error ◽  
Estimation Method ◽  
Pressure Variation ◽  
Estimation Errors ◽  
The Real ◽  
Radiated Noise ◽  
Comparison Results ◽  
Radiated Sound ◽  
Pressure Estimation

A new method, which combines the measurement and the estimation of the radiated noise variation, is proposed in this paper to predict the real-time radiated sound pressure. The estimation errors of the pressure variation are calculated and compared with the pressure estimation errors, using the Boundary Element Method(BEM). The comparison results show that the errors of the pressure variation estimation method are smaller than direct sound pressure estimation at the eigenfrequencies and most frequencies. The method can be used to decrease the real-teime radiated sound pressure estimation error.

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

Aerodynamic noise from an asymmetric airfoil with perforated extension plates at the trailing edge

2020 ◽  
pp. 1475472X2097838
Author(s):  
CK Sumesh ◽  
TJS Jothi
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Pore Diameter ◽  
Low Frequency ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Trailing Edge ◽  
High Frequency Noise ◽  
Displacement Thickness

This paper investigates the noise emissions from NACA 6412 asymmetric airfoil with different perforated extension plates at the trailing edge. The length of the extension plate is 10 mm, and the pore diameters ( D) considered for the study are in the range of 0.689 to 1.665 mm. The experiments are carried out in the flow velocity ( U∞) range of 20 to 45 m/s, and geometric angles of attack ( αg) values of −10° to +10°. Perforated extensions have an overwhelming response in reducing the low frequency noise (<1.5 kHz), and a reduction of up to 6 dB is observed with an increase in the pore diameter. Contrastingly, the higher frequency noise (>4 kHz) is observed to increase with an increase in the pore diameter. The dominant reduction in the low frequency noise for perforated model airfoils is within the Strouhal number (based on the displacement thickness) of 0.11. The overall sound pressure levels of perforated model airfoils are observed to reduce by a maximum of 2 dB compared to the base airfoil. Finally, by varying the geometric angle of attack from −10° to +10°, the lower frequency noise is seen to increase, while the high frequency noise is observed to decrease.

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