Noise Reduction of Elastic Structure Paste Viscoelastic Material Based on Complex Radius Vector of Virtual Source

2012 ◽  
Vol 164 ◽  
pp. 227-230
Author(s):  
Yu Ming Wang ◽  
Yuan An He ◽  
De Jiang Shang
Keyword(s):  
Noise Reduction ◽  
Viscoelastic Material ◽  
Cylindrical Shells ◽  
Complex Structure ◽  
Sound Field ◽  
Radius Vector ◽  
Superposition Method ◽  
Virtual Source ◽  
Radiated Sound ◽  
Reduction Characteristics

It is hard to theoretically calculate the noise reduction characteristics for underwater complex structure of paste viscoelastic material. This paper introduces complex radius vector inside radiator based on the advantages of singular integral provided by traditional virtual source superposition method to calculate the radiated sound field from finite cylindrical shells. This method adapts truncation regularization filter to overcome the effect of background noise to enhance the calculation accuracy and then use impedance transmission theory to calculate the noise reduction characteristics of the cylindrical shells paste viscoelastic material. Numerical simulations show the calculation accuracy is greatly dependent on the size and position of the distributed virtual sources. There exists an optimal complex radius to minimize the error.

401 Noise Reduction Characteristics of Noise Canceling in a Sound Field Environment

2014 ◽  
Vol 2014.63 (0) ◽  
pp. _401-1_-_401-2_
Author(s):  
Kazutaka ASAMOTO ◽  
Isao ITO ◽  
Takumi HATAOKA ◽  
Katumi MORIWAKI
Keyword(s):  
Noise Reduction ◽  
Sound Field ◽  
Field Environment ◽  
Reduction Characteristics ◽  
Noise Canceling

scholarly journals Noise Reduction Effect of Superhydrophobic Surfaces with Streamwise Strip of Channel Flow

2021 ◽  
Vol 11 (9) ◽  
pp. 3869
Author(s):  
Chen Niu ◽  
Yongwei Liu ◽  
Dejiang Shang ◽  
Chao Zhang
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Noise Reduction ◽  
Channel Flow ◽  
Superhydrophobic Surface ◽  
Sound Field ◽  
Flow Noise ◽  
Slip Boundary ◽  
Eddy Simulation ◽  
Reduction Effect

Superhydrophobic surface is a promising technology, but the effect of superhydrophobic surface on flow noise is still unclear. Therefore, we used alternating free-slip and no-slip boundary conditions to study the flow noise of superhydrophobic channel flows with streamwise strips. The numerical calculations of the flow and the sound field have been carried out by the methods of large eddy simulation (LES) and Lighthill analogy, respectively. Under a constant pressure gradient (CPG) condition, the average Reynolds number and the friction Reynolds number are approximately set to 4200 and 180, respectively. The influence on noise of different gas fractions (GF) and strip number in a spanwise period on channel flow have been studied. Our results show that the superhydrophobic surface has noise reduction effect in some cases. Under CPG conditions, the increase in GF increases the bulk velocity and weakens the noise reduction effect. Otherwise, the increase in strip number enhances the lateral energy exchange of the superhydrophobic surface, and results in more transverse vortices and attenuates the noise reduction effect. In our results, the best noise reduction effect is obtained as 10.7 dB under the scenario of the strip number is 4 and GF is 0.5. The best drag reduction effect is 32%, and the result is obtained under the scenario of GF is 0.8 and strip number is 1. In summary, the choice of GF and the number of strips is comprehensively considered to guarantee the performance of drag reduction and noise reduction in this work.

scholarly journals Analysis of the Influence of Different Bionic Structures on the Noise Reduction Performance of the Centrifugal Pump

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 886
Author(s):  
Cui Dai ◽  
Chao Guo ◽  
Yiping Chen ◽  
Liang Dong ◽  
Houlin Liu
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Centrifugal Pump ◽  
Great Influence ◽  
Frequency Doubling ◽  
Sound Field ◽  
Internal Flow ◽  
Test System ◽  
Centrifugal Pumps ◽  
External Characteristics

The strong noise generated during the operation of the centrifugal pump harms the pump group and people. In order to decrease the noise of the centrifugal pump, a specific speed of 117.3 of the centrifugal pump is chosen as a research object. The bionic modification of centrifugal pump blades is carried out to explore the influence of different bionic structures on the noise reduction performance of centrifugal pumps. The internal flow field and internal sound field of bionic blades are studied by numerical calculation and test methods. The test is carried out on a closed pump test platform which includes external characteristics and a flow noise test system. The effects of two different bionic structures on the external characteristics, acoustic amplitude–frequency characteristics and flow field structure of a centrifugal pump, are analyzed. The results show that the pit structure has little influence on the external characteristic parameters, while the sawtooth structure has a relatively great influence. The noise reduction effect of the pit structure is aimed at the wide-band noise, while the sawtooth structure is aimed at the discrete noise of the blade-passing frequency (BPF) and its frequency doubling. The noise reduction ability of the sawtooth structure is not suitable for high-frequency bands.

scholarly journals The Influence of PZT Actuators Positioning in Active Structural Acoustic Control

10.14311/968 ◽  
2007 ◽  
Vol 47 (4-5) ◽  
Author(s):  
P. Švec ◽  
V. Jandák
Keyword(s):  
Sound Field ◽  
Structural Vibration ◽  
Structural Acoustics ◽  
The Finite Element Method ◽  
Ansys Software ◽  
Structural Vibrations ◽  
Radiated Power ◽  
Acoustic Control ◽  
Radiated Sound ◽  
The Mathematical Model

This paper deals with the effect of secondary actuator positioning in an active structural acoustics control (ASAC) experiment. The ASAC approach is based on minimizing the sound radiation from structures to the far field by controlling the structural vibrations. In this article a rectangular steel plate structure was assumed with one secondary actuator attached to it. As a secondary actuator, a specially designed piezoelectric stripe actuator was used. We studied the effect of the position of the actuator on the pattern and on the radiated sound field of the structural vibration, with and without active control. The total radiated power was also measured. The experimental data was confronted with the results obtained by a numerical solution of the mathematical model used. For the solution, the finite element method in the ANSYS software package was used. 

scholarly journals A Prediction Method for Acoustic Intensity Vector Field of Elastic Structure in Shallow Water Waveguide

2020 ◽  
Vol 2020 ◽  
pp. 1-23
Author(s):  
Wenbo Wang ◽  
Desen Yang ◽  
Jie Shi
Keyword(s):  
Spatial Structure ◽  
Shallow Water ◽  
Transfer Functions ◽  
Source Parameters ◽  
Prediction Method ◽  
Sound Field ◽  
Elastic Structure ◽  
Superposition Method ◽  
Acoustic Intensity ◽  
Sound Energy

Compared with scalar sound field, vector sound field explained the spatial structure of sound field better since it not only presents the sound energy distribution but also describes the sound energy flow characteristics. Particularly, with more complicated interaction among different wavefronts, the vector sound field characteristics of an elastic structure in a shallow water waveguide are worthy of studying. However, there is no reliable prediction method for the vector sound field of an elastic structure with a high efficiency in a shallow water waveguide. To solve the problem, transfer functions in the waveguide have been modified with some approximations to apply for the vector sound field prediction of elastic structures in shallow water waveguides. The method is based on the combined wave superposition method (CWSM), which has been proved to be efficient for predicting scalar sound field. The rationality of the approximations is validated with simulations. Characteristics of the complex acoustic intensity, especially the vertical components are observed. The results show that, with constructive and destructive interferences in the depth direction, there could be quantities of crests and vortices in the spatial structure of time-dependent complex intensity, which manifest a unique dynamic characteristic of sound energy. With more complicated interactions among the wavefronts, a structure source could not be equivalent to a point source in most instances. The vector sound field characteristics of the two sources could be entirely different, even though the scalar sound field characteristics are similar. Meanwhile, source types, source parameters, ocean environment parameters, and geo parameters may have influence on the vector sound field characteristics, which could be explained with the normal mode theory.

The Use of Rigidity Properties in Cylindrical Shells for Noise Reduction

2006 ◽  
pp. 259-264
Author(s):  
R. Butkus ◽  
J. Deikus ◽  
Danielius Gužas ◽  
A. Šarlauskas
Keyword(s):  
Noise Reduction ◽  
Cylindrical Shells

The Effect of Direct Field Component on a Statistical Energy Analysis (SEA) Model

2013 ◽  
Vol 471 ◽  
pp. 279-284 ◽  
Author(s):  
Azma Putra ◽  
Al Munawir ◽  
W.M.F.W. Mohamad ◽  
J.I. Mohammad
Keyword(s):  
Field Component ◽  
Energy Analysis ◽  
Complex Structure ◽  
Sound Field ◽  
Injection Technique ◽  
Statistical Energy Analysis ◽  
Coupling Loss ◽  
Model Assumption ◽  
Power Injection ◽  
Acoustic Space

Statistical Energy Analysis (SEA) is a well-known method to analyze the flow of acoustic and vibration energy in a complex structure. The structure is divided into subsystems where the energy in each of the subsystem is assumed to be reverberant. This study investigates the application of SEA model in a 'damped' acoustic space where the direct field component from the sound source dominates the total sound field rather than a diffuse field in a reverberant space which the SEA model assumption is based on. A measurement was conducted in a scaled room divided into two acoustic spaces separated by a partition with an opening. Absorbent materials were installed on the room walls and the power injection technique was implemented to obtain the coupling loss factor (CLF) of the system. It is found that correction of the direct field component from the subsystem energy improves the prediction of the CLF of the system.

On the reductions of aerofoil-turbulence interaction noise through multi-wavelength leading edge serrations

2020 ◽  
pp. 095441002096574
Author(s):  
S Narayanan ◽  
Sushil Kumar Singh
Keyword(s):  
Noise Reduction ◽  
Maximum Amplitude ◽  
Leading Edge ◽  
Emission Angle ◽  
Broadband Noise ◽  
Dual Wavelength ◽  
Flat Plates ◽  
Wide Range ◽  
Multi Wavelength ◽  
Reduction Characteristics

This paper provides an experimental study into the use of multi-wavelength sinusoidal leading edge ( LE) serrations for enhancing the aerofoil-broadband noise reductions. The noise reduction performances of multi-wavelength serration profiles introduced on a flat plate are compared against those generated by single-wavelength profiles when applied separately. The multi-wavelength leading edge serration is made in such a way that its maximum amplitude is kept same as that of each single-wavelength ones to be compared. The present study reveals that the dual-wavelength serrations provide higher noise reductions over a narrow band of frequencies as compared to single and triple wavelength ones. Further, it reveals that the noise reduction characteristics of dual-wavelength serrated airfoils are similar to the flat plates. It shows that the baseline plate generate higher noise radiations for all emission angles as compared to leading edge serrated plates, but the common feature among them is the downstream directivity. For the range of frequencies 0.9 to 5 kHz, the highest directivity is seen at an emission angle of 55° for the baseline, while it occurs at 75° for the serrated plates. The dual wavelength serrations generate lowest acoustic radiations as compared to single and triple ones for all the emission angles. Also, it is noticed that the radiation levels of the dual serrations decrease with increase in amplitude of the serration, which shows that the longer dual serrations generate lowest acoustic radiations. Thus, the present study illustrates that the dual wavelength leading edge serrations act as the best passively modified serration profiles for achieving the highest noise reductions over a wide range of frequencies as compared to single and triple wavelength ones.

Prediction for Sound Radiated Power from Submerged Double Cylindrical Shells Based on Measuring Vibration of Inner Shell

2013 ◽  
Vol 779-780 ◽  
pp. 602-606 ◽  
Author(s):  
Chao Zhang ◽  
De Jiang Shang ◽  
Qi Li
Keyword(s):  
Prediction Error ◽  
Cylindrical Shells ◽  
Prediction Method ◽  
Superposition Method ◽  
Power Curve ◽  
Mean Square ◽  
Average Prediction Error ◽  
Radiated Power ◽  
Modal Superposition Method ◽  
Good Agreement

A prediction method for the sound radiated power from submerged double cylindrical shells based on measuring vibration of inner shell is presented. The prediction model of submerged double cylindrical shells is established by using modal superposition method. Applied the ratio of the measuring value and theoretical value of the acceleration in one point or mean square velocity of inner shell, and combined with the theoretical value of the sound radiated power, the predicted value of the sound radiated power is derived. The corresponding experiment is carried out in lake. And then the measuring power curve is compared with the predicted power curve based on this method. The result shows that they have good agreement and the average prediction error is less than 2dB.

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