scholarly journals Sound Radiation from an Elastically Restrained Plate Covered by an Acoustic Decoupling Layer

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Gang Wang ◽  
Wan-You Li ◽  
Wen Long Li ◽  
Jingtao Du
Keyword(s):  
Sound Radiation ◽  
Sound Field ◽  
Sound Intensity ◽  
Parametric Modeling ◽  
Model Studies ◽  
Coupling System ◽  
Ritz Procedure ◽  
Reduction Effect ◽  
Elastically Restrained ◽  
Sound Reduction

The sound radiation from elastically restrained plates covered by a decoupling layer is studied using the Spectrogeometric Method (SGM), which is a meshless and parametric modeling technique. By adopting the Rayleigh-Ritz procedure and the Rayleigh integral, a vibroacoustic coupling system is established. This model studies the situation when the plate is immersed in heavy fluid, such as water, in which the strong coupling between the structure and sound field should be fully considered. The influence of the boundary conditions on the radiated sound power and sound reduction provided by the decoupling layer based on the locally reacting model is studied. The nonuniform distributed decoupling layer is also studied to analyze the sound reduction effect. The sound intensity on the outer surface of the decoupling layer is investigated and tends to be uniform along the plate scale with increasing thickness of the decoupling layer.

Analysis of Sound Reduction and Strong Drag Composite Concrete Fibers Gedebok Banana Results Delignification with Sodium Hydroxide Solvent (Naoh)

2018 ◽  
Vol 6 (02) ◽  
pp. 105-120
Author(s):  
Muhammad Rouf Suprayogi ◽  
Annisa Mufida ◽  
Edwin Azwar
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Lignin Content ◽  
Sound Intensity ◽  
Cellulose Fiber ◽  
Cellulose Content ◽  
Cellulose Powder ◽  
Drying Method ◽  
Normal Concrete ◽  
Sound Reduction

In composite science, desirable materials that are lighter but have the power and quality that can match or even exceed the material that has been there before. The purpose of this study was to investigate the effect of cellulose fiber addition from banana gedebok to tensile strength, compressive strength and damping of concrete composite sound. To achieve this objective, mixing of cellulose fibers with K-275 quality concrete mix with variation of 0% and 5% substitution in which the cellulose is varied in powder and wicker form. Delignification of lignin content from banana gedebok was done by soaking and drying method without any variation and yielding powder having cellulose content of 13,0388%, hemicellulose 18,2796% and lignin 0,6684%. This study produces concrete composites that have a tensile strength and a compressive strength lower than that of normal concrete. Normally reinforced concrete tensile strength value 94.5 kg / cm2, 71.4 kg / cm2 cellulose powder concrete and 90.3 kg / cm2 cellulose woven concrete. Normal concrete compressive strength value 334,22 kg / cm2, cellulose powder concrete 215,7 kg / cm2, and cellulose webbing concrete 157,98 kg / cm2. As for the power damping sound of cellulose webbing concrete has the highest damping power compared to other concrete with the absorbed sound intensity that is 52-68 dB

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.

Investigation of wind and sound field characteristics of multi-rotor unmanned aerial vehicle

2020 ◽  
Vol 51 (7-9) ◽  
pp. 158-163
Author(s):  
Huiru Cao ◽  
Haixiu Cheng ◽  
Wenjian Zhu
Keyword(s):  
Linear Relationship ◽  
Unmanned Aerial Vehicle ◽  
Wind Field ◽  
Sound Field ◽  
Sound Intensity ◽  
Experimental Platform ◽  
Distance Range ◽  
Aerial Vehicle ◽  
Set Up ◽  
Wind Intensity

Wind field and sound field characteristics are the key indexes for unmanned aerial vehicle. Therefore, in this study, the wind field and sound field characteristics of a quad-rotor unmanned aerial vehicle are investigated. First, the experimental platform was set up based on quad-rotor unmanned aerial vehicle. Second, the experiments were performed on the wind field and the sound field characteristics of the unmanned aerial vehicle at different working currents. Then, the experiment results were analysed. Meanwhile, the experimental results showed that the working current has a large impact on the wind field and the wind intensity increases as working current increases; as the working current increases, the sound field is enhanced and a linear relationship exists; within a certain distance range of the unmanned aerial vehicle, as distance increases, sound intensity dramatically decreases. The presented methods and results can not only be used to evaluate the performance of the electric multi-rotor unmanned aerial vehicle but also provide references for the further improvement of the performance of the unmanned aerial vehicle.

Sound Radiation Characteristics of Lightweight Roof Constructions Excited by Rain

1994 ◽  
Vol 1 (4) ◽  
pp. 249-270 ◽  
Author(s):  
Hiromi Suga ◽  
Hideki Tachibana
Keyword(s):  
Transmission Loss ◽  
Power Level ◽  
Sound Radiation ◽  
Sound Intensity ◽  
Sound Power ◽  
Radiation Characteristics ◽  
Natural Rainfall ◽  
Artificial Rainfall ◽  
Sound Power Level ◽  
Measurement Results

In order to investigate the sound radiation characteristics of lightweight roof constructions when excited by rainfall, an artificial rainfall apparatus was constructed to simulate natural rainfall conditions. From the measurement results, it can be seen that the facility developed is practically applicable for the examination of the sound radiation characteristics of rain noise. It was therefore used in the measurement of sound power of 20 lightweight roofs. In addition, the relationship between sound power level and sound transmission loss measured by the sound intensity method was investigated statistically. As a result, it has been shown that a linear relationship exists between them and there is a possibility of estimating the sound power level from the transmission loss.

Changes in Floor Impact Sound Insulation Performance with Time

2015 ◽  
Vol 752-753 ◽  
pp. 698-701
Author(s):  
Kyoung Woo Kim ◽  
Jun Oh Yeon ◽  
Kwan Seop Yang
Keyword(s):  
Physical Characteristic ◽  
Dynamic Stiffness ◽  
Vibration Reduction ◽  
Sound Insulation ◽  
Degree Of Reduction ◽  
Floor Structure ◽  
Reduction Effect ◽  
Sound Reduction ◽  
Insulation Performance

Floating floor structures installed with resilient materials are commonly used to reduce sound from floor impacts. Resilient materials minimize the transmission of vibrations by absorbing shock vibrations occurring on the upper part. The floor impact sound reduction performance of resilient materials is related to the dynamic stiffness, which is a physical characteristic of materials. However, the dynamic stiffness varies according to the increase in the loading time of the load that is installed on the upper part of resilient materials. The dynamic stiffness values increase with an increase in the loading time; an increased dynamic stiffness value decreases the vibration reduction effect. The present study focuses on a floor structure installed with resilient materials, and identifies the degree of reduction in floor impact sound insulation performance with the elapse of time. The insulation of sound from lightweight impact sound decreased with the elapse of time, whereas the heavyweight impact sound did not show significant changes.

Characteristics of Modal Sound Radiation of Finite Cylindrical Shells

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Tian Ran Lin ◽  
Chris Mechefske ◽  
Peter O’Shea
Keyword(s):  
Cylindrical Shells ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Field ◽  
Radiation Efficiency ◽  
Boundary Element Methods ◽  
Frequency Range ◽  
Nodal Lines ◽  
Infinite Cylindrical Shell ◽  
Modal Index

Characteristics of modal sound radiation of finite cylindrical shells are studied using finite element and boundary element methods in this paper. In the low frequency range, modal radiation efficiencies of finite cylindrical shells are found to asymptotically approach those of the corresponding infinite cylindrical shell when structural trace wavelengths of the cylindrical shells are greater than the acoustic wavelength. Modal radiation efficiencies for each group of modes having the same circumferential modal index decrease as the axial modal index increases. They converge to each other when the axial trace wavelength is much greater than the circumferential trace wavelength. The mechanism leading to lower radiation efficiency of modes with higher circumferential modal index of short cylinders is explained. Similar to those of flat plate panels, change in slope or waviness is observed in modal radiation efficiency curves of modes with higher order axial modal index at medium frequencies. This is attributed to the interference of sound radiated by neighboring vibrating cells when the distance between nodal lines of a vibrating mode is in the same order or smaller than the acoustic wavelength. The effects of the internal sound field on modal radiation efficiencies of a finite open-end cylinder are discussed.

Active Control of Low-Frequency Sound Radiation From Vibrating Panel Using Planar Sound Sources

2001 ◽  
Vol 124 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Kean Chen ◽  
Gary H. Koopmann
Keyword(s):  
Active Control ◽  
Near Field ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Field ◽  
Sound Power ◽  
Frequency Range ◽  
Sound Sources ◽  
Frequency Sound ◽  
Secondary Sources

Active control of low frequency sound radiation using planar secondary sources is theoretically investigated in this paper. The primary sound field originates from a vibrating panel and the planar sources are modeled as simply supported rectangular panels in an infinite baffle. The sound power of the primary and secondary panels are calculated using a near field approach, and then a series of formulas are derived to obtain the optimum reduction in sound power based on minimization of the total radiate sound power. Finally, active reduction for a number of secondary panel arrangements is examined and it is concluded that when the modal distribution of the secondary panel does not coincide with that of the primary panel, one secondary panel is sufficient. Otherwise four secondary panels can guarantee considerable reduction in sound power over entire frequency range of interest.

Acoustic Radiation of a Cylindrical Piezoelectric Power Transformer

2013 ◽  
Vol 80 (6) ◽  
Author(s):  
He Zhang ◽  
Guiru Ye ◽  
Zhicheng Zhang
Keyword(s):  
Acoustic Radiation ◽  
Power Transformer ◽  
Power Level ◽  
Sound Radiation ◽  
Sound Field ◽  
Piezoelectric Transducers ◽  
Radial Polarization ◽  
Metal Core ◽  
Sound Power Level ◽  
Surrounding Fluid

Theoretical analysis is performed for the sound radiation of a cylindrical power transformer composed of piezoelectric transducers with radial polarization. The transformer is driven in thickness-stretch mode, and an exact solution is obtained for the sound pressure and sound power level in the surrounding fluid. Representative examples are used to illustrate the sound field induced by the operation of the transformer. Numerical results indicate that the electrical impedance and the thickness ratio of actuator/sensor to metal core have considerable effects on sound radiation of the cylindrical power transformer.

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