The effect of conical adapters and choice of reference microphone when using the two-load method for measuring muffler transmission loss

Hua, Xin; Zhang, Y.; Herrin, D. W.

doi:10.1016/j.apacoust.2015.01.014

Cited by 22 publications

(8 citation statements)

References 13 publications

(24 reference statements)

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“…Based on the plane wave assumption in the inlet and outlet pipes, the two-load method is usually employed to measure the TL of the muffler. 13 Figure 1 shows the experimental principle diagram of the two-load method for the test muffler. A and B represent the incident and reflective acoustic waves in the inlet pipe, respectively.…”

Section: Basic Theorymentioning

confidence: 99%

Numerical analysis of the transmission loss of water muffler according to the two-load method

Gong

Jiang

Xuan

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part C:

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A numerical method for the transmission loss prediction of the water muffler has been provided according to the measuring process of the two-load method. The commonly used acoustic loads can be applied in the proposed method. The accuracy of the proposed method has been proved by comparing the calculated transmission loss with that from the traditional direct predicting method. And then the proposed method is used to discuss effects of test bench on transmission loss measurement. The predicted transmission loss curves are consistent reasonably based on different test models. The location of monitors relative to the muffler inlet and outlet has little influence on the result. But the distance between the two monitors upstream or downstream should be controlled within a certain range based on the concerning frequency band and the main pipe diameter. It is found that modes of the coupled system consisting of the test pipes and the water cause extra peaks on the transmission loss curve. The influence can be reduced by arranging appropriate fixed points. The proposed method can be used to to explain the reasonability and validity of the test bench design.

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Section: Basic Theorymentioning

confidence: 99%

Numerical analysis of the transmission loss of water muffler according to the two-load method

Gong

Jiang

Xuan

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…The program was based on the plane wave theory and uses the Visual Basic 6.0 to build and modify the duct muffling systems quickly with proper the geometrical and physical parameters, to examine the effects of design changes on the acoustic attenuation characteristics and finally to get an acceptable solution. Authors [21] was contributed to determine acoustic performance of muffler and can be reviewed for design and development of muffler. In his research paper two-load method was conducted for measuring muffler transmission loss also algorithm for computing the transmission loss was involved.…”

Section: Flow Distributionmentioning

confidence: 99%

A Review of Flow Acoustic Effects on a Commercial Automotive Exhaust System

Mohamad¹

2019

MVM

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Acoustic simulation methods are being increasingly used for practical exhaust system design of automotive. In many practical applications, the sound source emits, partly, a low frequency sound spectrum comprised of superposed discrete tones and partly, a higher frequency broadband spectrum. The turbulent vortices that develop in the boundary layer between the duct wall and the flowing medium are said to generate a selfexcited noise, that noise is broadband character. The self-excitation is enhanced when the flow is disturbed by irregularities in the duct wall. Unsteady compressible fluid flow through a duct is often encountered in many engineering applications and has been investigated by many researchers. When a pressure wave generated inside a duct is discharged from an open end of the duct, an impulsive wave that is usually characterized by high sound pressure level of short duration forms at the vicinity of the exit of the duct. Acoustic simulations solve the equations for motion, mass, momentum, and energy and can be divided into two methods, linear and non-linear. Through that literature review, we can analyse the methods and the latest development done on exhaust systems with regard to acoustic performance. The basic theory behind both approaches is explained as well as a source characterization technique that can be used to link the two methods. Some acoustic software tool has been applied to a variety of exhaust systems.

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“…Let us write the resultant matrix of equation (18) as, (19) As the end of the resonator is solidly terminated, there will be no flow at the end of the cavity (19), the acoustic pressure and volume velocity at the opening of the neck becomes…”

Section: Transfer Matrix Of Helmholtz Resonatormentioning

confidence: 99%

“…The transmission loss of the muffler is calculated by transfer matrix method and the result is compared to the result that obtained by an experiment. The experiment was done by two-load method using four microphones impedance tube [15][16][17][18][19][20]. The comparison is shown in Figure-6.…”

Section: Mathematical Modelmentioning

confidence: 99%

Effects of Parameters of Helmholtz Resonator on Transmission Loss of Hybrid Muffler

Zaw¹,

Abu²,

Fawazi³

et al. 2018

IJET

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Expansion chamber and Helmholtz resonators are widely used in noise control. In this paper, they are combined to use as a hybrid muffler. The analysis is done to investigate the influence of the parameters of Helmholtz resonator on transmission loss. The transfer matrix method is used in the analysis. The result of transmission loss from the transfer matrix method is validated with the result from experimental two-load method using four microphones impedance tube. After had the transmission loss of the hybrid muffler been validated, the study was proceeded to investigate the effects of parameters of Helmholtz resonator on the transmission loss. The root mean square value of transmission loss were also calculated to compare the transmission losses clearly. In this paper, we investigated the effect of length of the neck of Helmholtz resonator, the effect of diameter of the neck of Helmholtz resonator, the effect of the length of the Helmholtz resonator cavity and the effect of the diameter of the Helmholtz resonator cavity for stationary medium. It is found that the transmission loss is increased when the diameter of the neck of Helmholtz resonator is increased. When the length of the neck is reduced, the transmission loss is increased. The transmission loss can also be increased by reducing the diameter of resonator cavity. It is better to increase the transmission loss at low frequencies by increasing the length of the resonator cavity.

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The effect of conical adapters and choice of reference microphone when using the two-load method for measuring muffler transmission loss

Cited by 22 publications

References 13 publications

Numerical analysis of the transmission loss of water muffler according to the two-load method

Numerical analysis of the transmission loss of water muffler according to the two-load method

A Review of Flow Acoustic Effects on a Commercial Automotive Exhaust System

Effects of Parameters of Helmholtz Resonator on Transmission Loss of Hybrid Muffler

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