scholarly journals Influence of perforation and sound-absorbing material filling on acoustic attenuation performance of three-pass perforated mufflers

2018 ◽  
Vol 10 (1) ◽  
pp. 168781401774801 ◽  
Author(s):  
Hongpu Huang ◽  
Zhenlin Ji ◽  
Zhuoliang Li
Keyword(s):  
Finite Element Method ◽  
Transmission Loss ◽  
The Finite Element Method ◽  
Frequency Range ◽  
Acoustic Attenuation ◽  
Pressure Drops ◽  
Outlet Tube ◽  
Middle Chamber ◽  
Absorbing Material ◽  
Perforated Tube

The finite element method is employed to calculate the transmission loss of three-pass perforated reactive and hybrid mufflers. The effects of perforated tubes and bulkheads on the transmission loss of three-pass reactive mufflers are investigated numerically. Two types of hybrid mufflers are considered, and the effects of sound-absorbing material filling and packed outlet tube on the acoustic attenuation performance of mufflers are analyzed. The perforations of the tubes and bulkheads and sound-absorbing material filling are demonstrated to have significant influence on the acoustic attenuation behaviors of the mufflers. The perforation of the tubes and bulkheads may shift the resonance from the low- to middle-frequency range. The sound-absorbing material filling in the middle chamber improves the acoustic attenuation performance at middle to higher frequencies and provides a relatively flat and broadband acoustic attenuation. It is found that the solid inlet or outlet tube replacing the perforated tube and sound-absorbing material filling in the middle chamber increases the pressure drops, while the rest configurations change the pressure drops slightly.

Computational Fluid Dynamics-Based Numerical Analysis of Acoustic Attenuation and Flow Resistance Characteristics of Perforated Tube Silencers

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Chen Liu ◽  
Zhenlin Ji
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Drop ◽  
Time Domain ◽  
Transmission Loss ◽  
Air Flow ◽  
Acoustic Attenuation ◽  
Pressure Drops ◽  
Wave Range ◽  
Perforated Tube

The 3D time-domain computational fluid dynamics (CFD) approach is used to calculate the acoustic attenuation performance of perforated tube silencers without and with flow. For the crossflow perforated tube silencer and straight-through perforated tube silencers, the transmission loss predictions agree well with the experimental measurements available in the literature. Then, the 3D time-domain CFD approach is employed to investigate the effects of flow velocity and temperature on the acoustic attenuation performance of perforated tube silencers. The numerical results demonstrated that the transmission loss is increased at most frequencies for the crossflow perforated tube silencer as the air flow increases, while the air flow has little influence on the acoustic attenuation in the plane wave range and increases the acoustic attenuation at higher frequencies for the straight-through perforated tube silencers. Increasing the air temperature shifts the transmission loss curve to higher frequency and lowers the resonance peaks somewhat. The pressure drops of perforated tube silencers are predicted by performing the 3D steady flow computation using CFD. The pressure drop of the crossflow perforated tube silencer is much higher than those of the straight-through perforated tube silencer at the same flow conditions, and the pressure drop of the straight-through perforated tube silencer increases gradually as the porosity increases.

Mode Interactions and Sound Power Transmission Loss of Expansion Chambers

2006 ◽  
Vol 129 (2) ◽  
pp. 141-147 ◽  
Author(s):  
C. K. Lau ◽  
S. K. Tang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Plane Wave ◽  
Industrial Application ◽  
Power Transmission ◽  
Transmission Loss ◽  
Wave Power ◽  
Sound Power ◽  
The Finite Element Method ◽  
Mode Interactions

The mode interactions and the sound transmission loss across the expansion chambers with and without tapered sections are studied by the finite element method in the present investigation. Results from chambers with symmetrical inlet and outlet suggest lower sound power transmission loss at frequencies below that of the first symmetrical transverse chamber mode when the tapered section angle is reduced. Weak sound power transmission loss is also observed for this chamber type at frequency higher than that of the first symmetrical duct mode. Numerous high and low sound power transmission loss regions are observed between these two eigenfrequencies. Higher plane wave power transmission loss can be found at smaller tapered section angle only if one of the chamber endings is not tapered. Such chamber bears important industrial application.

scholarly journals Selected aspects of numerical modelling in prediction of building vibrations due to traffic

2018 ◽  
Vol 196 ◽  
pp. 01055
Author(s):  
Sławomir Dudziak ◽  
Zofia Kozyra
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Modelling ◽  
The Finite Element Method ◽  
Frequency Range ◽  
Mass Estimation ◽  
Structure Response ◽  
Dynamic Analyses ◽  
Transportation Routes ◽  
The Impact

Dynamic analyses play an important role in the process of designing buildings in the vicinity of transportation routes. The Finite Element Method is the most popular modelling technique, because it allows to simulate the structure response in the higher frequency range properly. However, the results of such analyses depend on many factors and can differ a lot. This paper discusses the impact of the building mass estimation and neglecting or including damping in the analysis on the assessment of influence of vibrations due to traffic on people.

Application of a Discrete Transfer Matrix Method in Analysis of Acoustic Attenuation Performance of Complex Perforated Pipe Mufflers

2013 ◽  
Vol 419 ◽  
pp. 140-144
Author(s):  
Huo Rui ◽  
Meng Bei ◽  
Zhang Lei
Keyword(s):  
Transfer Matrix ◽  
Transmission Loss ◽  
Influential Factors ◽  
Calculation Formula ◽  
Acoustic Attenuation ◽  
Noise Elimination ◽  
Discrete Method ◽  
Factors Analysis ◽  
Perforated Pipe ◽  
Perforated Tube

The article is about an application of a discrete method for analyzing acoustic attenuation performance of perforated tube mufflers. Acoustic transfer matrix of a tiny perforated tube section which contains one single hole is deduced based on basic hydromechanics equations. Then the work is developed into a general formula for resolving sound transmission loss of one perforated silencer unit consisting of multiple parallel perforated pipes. Result of the calculation formula is compared with that of acoustic finite element method. One more example is presented on influential factors analysis for noise elimination performance of a practical complex perforation muffler.

OPTIMAL DESIGN OF A 1-3 PIEZOCOMPOSITE TONPILZ TRANSDUCER BY MEANS OF THE FINITE ELEMENT METHOD

2008 ◽  
Vol 22 (11) ◽  
pp. 1087-1092 ◽  
Author(s):  
DA LIE PEI ◽  
YONGRAE ROH
Keyword(s):  
Finite Element Method ◽  
Sound Pressure ◽  
Optimization Technique ◽  
Pressure Level ◽  
Frequency Bandwidth ◽  
The Finite Element Method ◽  
Frequency Range ◽  
Design Variables ◽  
Structural Variables ◽  
Functional Forms

Underwater Tonpilz transducer is designed with 1-3 piezocomposite materials to overcome the problems with conventional piezoceramic transducers. With the FEM, the variation of the resonance frequency, bandwidth and sound pressure of the transducer are analyzed in relation to the structural variables of the transducer. Through statistical multiple regression analysis of the results, functional forms of the transducer performance are derived in terms of design variables. By applying the constrained optimization technique, SQP-PD, to the derived functions, the optimal structure of the transducer is determined that can provide the highest sound pressure level at a given resonant frequency over a pre-determined frequency range. The validity of the optimized results is confirmed through comparison of the optimal performance with that of the FEA.

ACOUSTIC ATTENUATION CHARACTERISTICS OF STRAIGHT-THROUGH PERFORATED TUBE SILENCERS AND RESONATORS

2008 ◽  
Vol 16 (03) ◽  
pp. 361-379 ◽  
Author(s):  
Z. L. JI
Keyword(s):  
Performance Prediction ◽  
Transmission Loss ◽  
Three Dimensional ◽  
Geometrical Parameters ◽  
Mean Flow ◽  
Acoustic Attenuation ◽  
One Dimensional ◽  
The One ◽  
Attenuation Characteristics ◽  
Perforated Tube

The one-dimensional analytical solutions are derived and three-dimensional substructure boundary element approaches are developed to predict and analyze the acoustic attenuation characteristics of straight-through perforated tube silencers and folded resonators without mean flow, as well as to examine the effect of nonplanar waves in the silencers and resonators on the acoustic attenuation performance. Comparisons of transmission loss predictions with the experimental results for prototype straight-through perforated tube silencers demonstrated that the three-dimensional approach is needed for accurate acoustic attenuation performance prediction at higher frequencies, while the simple one-dimensional theory is sufficient at lower frequencies. The BEM is then used to investigate the effects of geometrical parameters on the acoustic attenuation characteristics of straight-through perforated tube silencers and folded resonators in detail.

Acoustic performance analysis of Helmholtz resonators with conical necks and its application

2019 ◽  
Vol 67 (3) ◽  
pp. 155-167 ◽  
Author(s):  
Haitao Liu
Keyword(s):  
Finite Element ◽  
Prediction Model ◽  
Transmission Loss ◽  
Low Frequency ◽  
Wide Band ◽  
Acoustic Properties ◽  
Frequency Range ◽  
Acoustic Attenuation ◽  
Acoustic Performance ◽  
Helmholtz Resonators

The acoustic properties of the Helmholtz resonators with conical necks, which have broad acoustic attenuation band performance in the low frequency range, are investigated in this study. In order to investigate its wide-band acoustic attenuation mechanism, three-dimensional finite element models for the Helmholtz resonators with different necks are built respectively. The acoustic performance prediction model based on the one-dimensional analytical approach with acoustic length corrections is built to calculate the transmission loss results more efficiently, and the formula for calculating the resonance frequency is also derived. Then, the prediction model and the formula are verified by finite element method and experiment, which show good agreements. As a result, the prediction model is applied to analyze the sound attenuation properties of the Helmholtz resonators with conical necks, and the results show that the acoustic attenuation bandwidth in the low frequency range is improved by increasing the taper angle of the neck. At last, the approaches for the Helmholtz resonators with conical necks are applied to design an actual middle silencer of a passenger car. The results show that the designed middle silencer performs much better than the original one, which can effectively eliminate the exhaust order noise to meet the standard of exhaust noise control. The test results fully reveal that the Helmholtz resonators with conical necks in the muffler can play a better role in eliminating exhaust order noise, and the approaches proposed in this article can effectively guide the design of Helmholtz resonators with conical necks.

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