Volume 21, Issue 1 (2024)
ioh 2024, 21(1): 116-127 |
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Alimohamadi I, Nouraei M, AmirArsalan khan A, Yarahmadi R, Farokhi M. Modeling the effect of the number and angle of the baffle on the sound transmission loss in reactive muffler. ioh 2024; 21 (1) :116-127
URL: http://ioh.iums.ac.ir/article-1-3447-en.html
URL: http://ioh.iums.ac.ir/article-1-3447-en.html
Iran University of Medical Sciences , farokhi1.ma@gmail.com
Abstract: (378 Views)
Introduction: The sound coming from the exhaust of cars is the main cause of noise pollution in the urban environment. Mufflers are used as a passive noise control device to reduce the sound coming from the exhaust of cars. The effectiveness of mufflers in reducing the volume of sound depends on various factors. Achieving the right shape and dimensions for the internal components of mufflers can help design mufflers with high sound transmission loss and optimal fluid pressure loss. Therefore, the change in the muffler components and the effect of the placement angle and the number of baffles in the fluid flow path on the sound transmission loss in reactive mufflers have been investigated in this research through software simulation.
Materials and Methods: In the current study, software modeling using COMSOL has been used to investigate the effect of the studied geometrical variables on the sound transmission loss in the muffler. And by changing the geometric variables of the muffler, such as the number and opening angle of the muffler baffles, different designs were obtained and the results obtained were compared to the effect of each variable.
Results: The results of this study indicated that the change in each of the geometric variables has a different effect on the muffler sound transmission loss in different frequency ranges. So that despite the increase in the average sound transmission loss with the increase in the number and angle of the baffles, this factor is greatly reduced in certain frequency ranges.
Discussion: According to the findings of this research, the sound transmission loss of the different studied models is low at low frequencies and increases with increasing frequency. Also, reactive mufflers show the most acoustic efficiency in narrow frequency ranges, especially in high frequencies, and the reason for the reduction in transmission loss in some frequencies can be related to the fact that the resonance frequency of the muffler is higher than the frequency of the sound under investigation. In addition to this, by increasing the angle or opening of the baffle, the viscosity and density of the fluid inside the muffler increases, and the acoustic resistance increases and, as a result, the transmission loss increases.
Conclusion: COMSOL software can be used to predict the acoustic performance of mufflers and its results can be used to improve the design. This method helps to improve the design of mufflers easier and faster to increase the loss of sound transmission in them. Also, the number and angle of baffles inside the expansion chamber of reactive mufflers increases the sound transmission loss. Therefore, in the design of mufflers, it is possible to use angled baffles with the right number and angle to increase the sound transmission loss of the muffler at the target frequency.
Materials and Methods: In the current study, software modeling using COMSOL has been used to investigate the effect of the studied geometrical variables on the sound transmission loss in the muffler. And by changing the geometric variables of the muffler, such as the number and opening angle of the muffler baffles, different designs were obtained and the results obtained were compared to the effect of each variable.
Results: The results of this study indicated that the change in each of the geometric variables has a different effect on the muffler sound transmission loss in different frequency ranges. So that despite the increase in the average sound transmission loss with the increase in the number and angle of the baffles, this factor is greatly reduced in certain frequency ranges.
Discussion: According to the findings of this research, the sound transmission loss of the different studied models is low at low frequencies and increases with increasing frequency. Also, reactive mufflers show the most acoustic efficiency in narrow frequency ranges, especially in high frequencies, and the reason for the reduction in transmission loss in some frequencies can be related to the fact that the resonance frequency of the muffler is higher than the frequency of the sound under investigation. In addition to this, by increasing the angle or opening of the baffle, the viscosity and density of the fluid inside the muffler increases, and the acoustic resistance increases and, as a result, the transmission loss increases.
Conclusion: COMSOL software can be used to predict the acoustic performance of mufflers and its results can be used to improve the design. This method helps to improve the design of mufflers easier and faster to increase the loss of sound transmission in them. Also, the number and angle of baffles inside the expansion chamber of reactive mufflers increases the sound transmission loss. Therefore, in the design of mufflers, it is possible to use angled baffles with the right number and angle to increase the sound transmission loss of the muffler at the target frequency.
Type of Study: Research |
Subject:
Noise
Received: 2023/09/12 | Accepted: 2024/07/29 | Published: 2024/05/30
Received: 2023/09/12 | Accepted: 2024/07/29 | Published: 2024/05/30
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