Study on Performance of Automobiles Muffler Based on Sound Transfer Matrix Theory

2012 ◽  
Vol 197 ◽  
pp. 134-138 ◽  
Author(s):  
Qi Guo Hu
Keyword(s):  
Transfer Matrix ◽  
Matrix Theory ◽  
Transmission Loss ◽  
Low Frequency ◽  
Expansion Chamber ◽  
Fluid Analysis ◽  
Average Transmission ◽  
Tube Expansion ◽  
Insertion Tube ◽  
Single Insertion

According to the characteristics of automobiles exhaust noise of high pressure level and middle-low frequency, combining sound transfer matrix theory and FEM-Fluid analysis method, simulations of the transmission loss with non-insertion tube expansion chamber muffler, single insertion tube expansion chamber muffler and dual insertion tube expansion chamber muffler are carried out, which obtain the transmission loss curves of mufflers in different structures and different perforation rates. The results show that the max transmission loss and the average transmission loss of the muffler with perforation rate of 5% are greater than that of 3% and 10% below the low frequency of 200Hz; dual insertion tube expansion chamber muffler not only can increase the transmission loss below the frequency of 4000Hz, but also can effectively improve the performance of the mufflers in which have non-perforation tube and single insertion tube at some frequency points. The results of research can provide technical reference for exhaust muffler design of automotive.

A Simple Method for Measuring Muffler Transmission Loss With PU Probes

2013 ◽  
Author(s):  
Li Yan ◽  
Weikang Jiang
Keyword(s):  
Transfer Matrix ◽  
Particle Velocity ◽  
Transmission Loss ◽  
Low Frequency ◽  
Frequency Measurement ◽  
Decomposition Methods ◽  
Simple Method ◽  
Straightforward Method ◽  
Alternative Approach ◽  
Set Up

The conventional approaches for measuring muffler transmission loss based on measurement in impedance tube are mainly decomposition methods and transfer matrix method. The decomposition method needs an anechoic termination, but it is not easy in some cases particularly for low frequency measurement. Two-load method and two-source method based on transfer matrix techniques are considered to be an alternative approach which does not require an anechoic termination. PU probe can measure both sound pressure and particle velocity, which is applied to some acoustic measurement such as absorption coefficient in recent years. A straightforward method for measuring muffler transmission loss by two PU probes measuring particle velocity at the inlet and outlet of muffler is presented. The four-pole parameters of the muffler can be calculated directly. The transmission loss measured by the PU method agrees well with the result measured by conventional four-pole method and FEM result. To instruct the approach, the influence of measurement distance between PU probe and the inlet or outlet of muffler and ambient noise are analyzed, which gives comprehensive suggestions for measurement set up.

scholarly journals Analysis of Composite Scrubber with Built-In Silencer for Marine Engines

2021 ◽  
Vol 9 (9) ◽  
pp. 962
Author(s):  
Myeong-rok Ryu ◽  
Kweonha Park
Keyword(s):  
Noise Reduction ◽  
Transmission Loss ◽  
Flow Characteristics ◽  
Low Frequency ◽  
Frequency Region ◽  
Reverse Direction ◽  
Sulfur Oxide ◽  
Noise Characteristics ◽  
Average Transmission ◽  
Reduction Effect

The International Maritime Organization (IMO) is strengthening regulations on reducing sulfur oxide emissions, and the demand for reducing exhaust noise affecting the environment of ships is also increasing. Various technologies have been developed to satisfy these needs. In this paper, a composite scrubber for ships that can simultaneously reduce sulfur oxide and noise was proposed, and the flow characteristics and noise characteristics were analyzed. For the silencer, vane type and resonate type were applied. In the case of the vane type, the effects of the direction, size, and location of the vane were analyzed, and in the case of the resonate type, the effects of the hole location and the number of holes were analyzed. The result shows that the length increase of the vane increased the average transmission loss and had a great effect, especially in the low frequency region. The transmission loss increased when the vane was installed outside, and the noise reduction effect was excellent when the vane was in the reverse direction. In the resonate type, increasing the number of holes is advantageous for noise reduction. The condition for maximally reducing noise in the range not exceeding 840 Pa, which is 70% of the allowable back pressure, is a vane length of 225 mm in the outer vane reverse type. The pressure drop under this condition was 777 Pa, and the average transmission losses in the low frequency region and the entire frequency region were 43.5 and 54.5 dB, respectively.

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

2018 ◽  
Vol 7 (3.17) ◽  
pp. 151
Author(s):  
Thiha Zaw ◽  
Aminudin Abu ◽  
Noor Fawazi ◽  
A M. Wahab
Keyword(s):  
Transfer Matrix ◽  
Transfer Matrix Method ◽  
Matrix Method ◽  
Transmission Loss ◽  
Helmholtz Resonator ◽  
Transmission Losses ◽  
Expansion Chamber ◽  
Low Frequencies ◽  
Helmholtz Resonators ◽  
Resonator Cavity

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.  

scholarly journals Tuning a Two-Chamber Muffler for Wide-Band Transmission Loss

2020 ◽  
Vol 25 (2) ◽  
pp. 248-253
Author(s):  
M.L. Munjal
Keyword(s):  
Transmission Loss ◽  
Velocity Ratio ◽  
Low Frequency ◽  
Wide Band ◽  
Firing Frequency ◽  
Automotive Exhaust ◽  
Expansion Chamber ◽  
Significant Term ◽  
Wide Band Transmission ◽  
Exhaust Noise

The design of a muffler with wide-band transmission loss (TL) is a basic requirement for automotive exhaust systems where the exhaust noise is spread over several harmonics of the engine firing frequency. This has led to the concept of a double-tuned expansion chamber. In the present paper, the concept of double-tuning is extended to the two-chamber mufflers. The author's classical Velocity Ratio Algorithm is used here to analyze and design such a muffler. The relevant two-row array is manipulated and simplified to arrive directly at the single most significant term out of the 81 non-dimensional terms constituting the relevant Velocity Ratio. Examination of this single term reveals acoustics of the raised wide-band domes of the TL spectrum of the double-tuned two-chamber (DT2C) muffler vis-a-vis that of an equivalent longer double-tuned single-chamber muffler. Except for a low-frequency trough, its TL curve covers the entire frequency range of interest for control of automotive exhaust noise. It is also shown that the corresponding side-inlet side-outlet (SISO) DT2C muffler configuration has an identically similar wide-band TL spectrum to that of the co-axial muffler configuration. Finally, some guidelines are laid out for designing a DT2C muffler.

Effect of leakage and blockage on the acoustic behavior of particle filters

2019 ◽  
Vol 67 (6) ◽  
pp. 483-492
Author(s):  
Seonghyeon Baek ◽  
Iljae Lee
Keyword(s):  
Transfer Matrix ◽  
Particle Filters ◽  
Acoustic Analysis ◽  
Transmission Loss ◽  
One Dimensional ◽  
Filter System ◽  
The Difference ◽  
The One ◽  
Analytical Approaches ◽  
Good Agreement

The effects of leakage and blockage on the acoustic performance of particle filters have been examined by using one-dimensional acoustic analysis and experimental methods. First, the transfer matrix of a filter system connected to inlet and outlet pipes with conical sections is measured using a two-load method. Then, the transfer matrix of a particle filter only is extracted from the experiments by applying inverse matrices of the conical sections. In the analytical approaches, the one-dimensional acoustic model for the leakage between the filter and the housing is developed. The predicted transmission loss shows a good agreement with the experimental results. Compared to the baseline, the leakage between the filter and housing increases transmission loss at a certain frequency and its harmonics. In addition, the transmission loss for the system with a partially blocked filter is measured. The blockage of the filter also increases the transmission loss at higher frequencies. For the simplicity of experiments to identify the leakage and blockage, the reflection coefficients at the inlet of the filter system have been measured using two different downstream conditions: open pipe and highly absorptive terminations. The experiments show that with highly absorptive terminations, it is easier to see the difference between the baseline and the defects.

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