An exhaust muffler optimization method

Abstract

The application provides an exhaust muffler optimization method, which comprises the following steps: when the transmission loss of the exhaust muffler at a certain frequency is less than a design requirement value, if the exhaust muffler is a resistive muffler, checking the thickness or the sound absorption coefficient of the resistive material on the inlet or outlet inner pipe of the exhaust muffler, the length of each cavity of the exhaust muffler, the inlet or outlet inner pipe or the diameter or the number of perforations on the partition plate, the cross-sectional shape of the exhaust muffler, and the influence of the above factors on the transmission loss at the frequency; if the exhaust muffler is not a resistive muffler, the thickness or the sound absorption coefficient of the resistive material on the inlet or outlet inner pipe is not checked, and after the influencing factors are found, the influencing factors are adjusted in the exhaust muffler model, so that the transmission loss at the frequency reaches the design requirement value; the exhaust muffler entity is correspondingly modified according to the adjustment content, and then the vehicle test verification is carried out. The application can realize the optimization of the exhaust muffler and improve the sound absorption capacity of the exhaust muffler.

Description

Technical Field

[0001] This invention belongs to the field of vehicle exhaust muffler technology, specifically relating to an optimization method for exhaust mufflers. Background Technology

[0002] With the development of today's automotive market, the NVH (Noise, Vibration, Harshness) performance of a vehicle has gradually become an important factor for consumers when purchasing a car. The NVH performance of the exhaust system is one of the key indicators affecting the overall NVH performance of a vehicle. An important indicator for evaluating the NVH performance of an exhaust muffler is its noise reduction capacity, which is usually evaluated using transmission loss. Transmission loss refers to the difference in sound power level between the inlet and outlet of the muffler, indicating the attenuation of sound energy after passing through the muffler element. Generally, the design requirement for the transmission loss of automotive exhaust mufflers is a transmission loss of no less than 20dB. If the transmission loss of the exhaust muffler does not meet this design requirement (i.e., the transmission loss is less than 20dB) at a certain frequency, a booming sound will typically be heard inside the vehicle during acceleration at that frequency.

[0003] Existing solutions primarily rely on the experience of NVH engineers to analyze and optimize exhaust mufflers. This approach is highly subjective, and the effectiveness of the improvement depends on the individual experience of the NVH engineer, failing to address the problem of insufficient transmission loss in exhaust mufflers in a targeted, rapid, and effective manner. Therefore, designing an optimization method to effectively identify the causes of insufficient transmission loss in exhaust mufflers and improve their noise reduction performance has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide an exhaust muffler optimization method to solve the above-mentioned technical problems in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An exhaust muffler optimization method includes the following steps:

[0007] Step S1: When the transmission loss of the exhaust muffler at a certain frequency is less than the design requirement, determine whether the exhaust muffler is a resistive muffler. If yes, proceed to step S2; if no, proceed to step S3.

[0008] Step S2: In the exhaust muffler model, adjust the thickness or noise reduction coefficient of the resistive material on the intake inner pipe and the exhaust inner pipe of the exhaust muffler. After adjustment, simulate and analyze whether the transmission loss at this frequency is greater than the design requirement. If yes, proceed to step S7; otherwise, proceed to step S3.

[0009] Step S3: Remove the resistive material from the intake and exhaust pipes, then disassemble each chamber of the exhaust muffler and calculate the transmission loss of each chamber. If the transmission loss of a certain chamber at a certain frequency is less than the design requirement, adjust the length and volume of the chamber and then proceed to step S7; otherwise, proceed to step S4.

[0010] Step S4: Adjust the length of the intake or exhaust pipe. After adjustment, perform simulation analysis to confirm whether the transmission loss at that frequency is greater than the design requirement. If yes, proceed to step S7; otherwise, proceed to step S5.

[0011] Step S5: Adjust the diameter and number of holes in the intake or exhaust pipe or partition. After adjustment, perform simulation analysis to confirm whether the transmission loss at this frequency is greater than the design requirement. If yes, proceed to step S7; otherwise, proceed to step S6.

[0012] Step S6: Adjust the cross-sectional shape of the exhaust muffler, and perform simulation analysis after adjustment to confirm whether the transmission loss at this frequency is greater than the design requirement. If so, proceed to step S7.

[0013] Step S7: Based on the adjustments, make corresponding modifications to the exhaust muffler, and then install it on the vehicle for testing and verification.

[0014] Preferably, in step S4, after adjusting the length of the intake or exhaust inner tube, if the minimum value of the transmission loss on the transmission loss curve obtained from the simulation analysis is to the left of the maximum value of the transmission loss, then the length of the inner tube is extended; otherwise, the length of the inner tube is shortened. Then, the length of the inner tube is adjusted again, and simulation analysis is performed. If the maximum value of the transmission loss is closer to the minimum value of the transmission loss compared to before the adjustment, then it is determined that the length of the inner tube affects the noise reduction capability and needs to be improved; otherwise, proceed to step S5.

[0015] Preferably, when adjusting the length of the intake or exhaust inner tube, the interval between each length adjustment is 150mm to 250mm.

[0016] Preferably, the length adjustment interval is 200mm.

[0017] Preferably, when adjusting the length of the intake or exhaust inner tube, the length of the exhaust inner tube should be adjusted first, and then the length of the intake inner tube should be adjusted.

[0018] Preferably, in step S5, after adjusting the diameter and number of perforations in the intake inner pipe, exhaust inner pipe, or partition, if the simulation analysis results show that the minimum transmission loss of the exhaust muffler is not at that frequency compared to before the adjustment, then the influencing factor of the muffler capacity is determined to be the diameter and number of perforations in the inner pipe or partition, and the diameter and number of perforations in the inner pipe or partition are adjusted; otherwise, proceed to step S6.

[0019] Preferably, in step S5, during adjustment, the diameter of the perforation is increased or decreased by 30% or 50% each time.

[0020] Preferably, in step S5, during adjustment, the number of perforations is increased or decreased by 30% or 50% each time.

[0021] The beneficial effects of this invention are as follows:

[0022] The exhaust muffler optimization method of the present invention can quickly and effectively find the cause of insufficient transmission loss of the exhaust muffler through simulation analysis of the adjusted exhaust muffler, and make targeted improvements to optimize the exhaust muffler. This can improve the noise reduction capacity of the exhaust muffler, thereby effectively improving the NVH performance of the whole vehicle and enhancing the driving comfort of the vehicle. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly described below, and the specific embodiments of the present invention will be further described in detail with reference to the drawings, wherein...

[0024] Figure 1 A flowchart of the exhaust muffler optimization method provided in this embodiment of the invention:

[0025] Figure 2 A schematic diagram of an exhaust muffler provided in an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of a partition provided in an embodiment of the present invention;

[0027] Figure 4 Transmission loss curve of the exhaust muffler provided in the embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of each cavity in the exhaust muffler provided in an embodiment of the present invention;

[0029] Figure 6 This is a transmission loss curve diagram of the extended outlet cannula provided in an embodiment of the present invention;

[0030] Figure 7The transmission loss curve after adjusting the cross-sectional shape of the exhaust muffler provided in the embodiment of the present invention.

[0031] Marked in the attached diagram:

[0032] 11. Intake inner tube; 12. Exhaust inner tube; 13. Partition; 14. Perforation.

[0033] 15. Transverse internal cannula; 21. First cavity; 22. Second cavity; 23. Third cavity

[0034] 24. Fourth cavity. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the present solution will be further described in detail below with reference to specific embodiments.

[0036] like Figure 1 As shown, this embodiment of the invention provides a method for optimizing an exhaust muffler, which includes the following steps:

[0037] Step S1: When the transmission loss of the exhaust muffler at a certain frequency is less than the design requirement, determine whether the exhaust muffler is a resistive muffler. If yes, proceed to step S2; if no, proceed to step S3.

[0038] Step S2: In the exhaust muffler model, adjust the thickness or noise reduction coefficient of the resistive material on the intake inner pipe and the exhaust inner pipe of the exhaust muffler. After adjustment, simulate and analyze whether the transmission loss at this frequency is greater than the design requirement. If yes, proceed to step S7; otherwise, proceed to step S3.

[0039] Step S3: Remove the resistive material from the intake and exhaust pipes, then disassemble each chamber of the exhaust muffler and calculate the transmission loss of each chamber. If the transmission loss of a certain chamber at a certain frequency is less than the design requirement, adjust the length and volume of the chamber and then proceed to step S7; otherwise, proceed to step S4.

[0040] Step S4: Adjust the length of the intake or exhaust pipe. After adjustment, perform simulation analysis to confirm whether the transmission loss at that frequency is greater than the design requirement. If yes, proceed to step S7; otherwise, proceed to step S5.

[0041] Step S5: Adjust the diameter and number of holes in the intake or exhaust pipe or partition. After adjustment, perform simulation analysis to confirm whether the transmission loss at this frequency is greater than the design requirement. If yes, proceed to step S7; otherwise, proceed to step S6.

[0042] Step S6: Adjust the cross-sectional shape of the exhaust muffler, and perform simulation analysis after adjustment to confirm whether the transmission loss at this frequency is greater than the design requirement. If so, proceed to step S7.

[0043] Step S7: Based on the adjustments, make corresponding modifications to the exhaust muffler, and then install it on the vehicle for testing and verification.

[0044] The exhaust muffler optimization method provided in this invention can quickly and effectively identify the causes of insufficient transmission loss in the exhaust muffler through simulation analysis of the adjusted exhaust muffler, and make targeted improvements to optimize the exhaust muffler. This can effectively improve the noise reduction capability of the exhaust muffler, thereby effectively improving the NVH performance of the whole vehicle and enhancing the driving comfort of the vehicle.

[0045] Further, in step S4, after adjusting the length of the intake or exhaust inner tube, if the minimum value of the transmission loss on the transmission loss curve obtained from the simulation analysis is to the left of the maximum value of the transmission loss, then the length of the inner tube is extended; otherwise, the length of the inner tube is shortened. Then, the length of the inner tube is adjusted again, and simulation analysis is performed. If the maximum value of the transmission loss is closer to the minimum value of the transmission loss compared to before the adjustment, then it is determined that the length of the inner tube affects the noise reduction capability and needs to be improved (i.e., when the length of the inner tube is adjusted to an appropriate value, the transmission loss at that frequency will be greater than the design requirement value). Otherwise, proceed to step S5.

[0046] Specifically, when adjusting the length of the intake or exhaust inner tube, the interval for each length adjustment is 150mm to 250mm.

[0047] Preferably, the length adjustment interval is 200mm.

[0048] Specifically, when adjusting the length of the intake or exhaust inner tube, adjust the length of the exhaust inner tube first, and then adjust the length of the intake inner tube.

[0049] Furthermore, in step S5, after adjusting the diameter and number of perforations in the intake or exhaust pipe or partition, if the simulation analysis results show that the minimum transmission loss of the exhaust muffler is not at that frequency (i.e., frequency shift has occurred) compared to before the adjustment, then the influencing factor of the muffler capability is determined to be the diameter and number of perforations in the pipe or partition. When the diameter and number of perforations in the pipe or partition are adjusted to an appropriate value, the transmission loss at that frequency can meet the design requirements, i.e., be greater than the design requirement value. Otherwise, proceed to step S6.

[0050] Preferably, in step S5, during adjustment, the diameter of the perforation is increased or decreased by 30% or 50% each time.

[0051] Specifically, in step S5, during adjustment, the number of perforations is increased or decreased by 30% or 50% each time. A preferred design requirement value is 20 dB, which is commonly used in the prior art.

[0052] It is understandable that when adjusting the exhaust muffler model in the software, a single variable for each adjustment item can be adjusted each time, and then a simulation analysis can be performed to accurately find the influencing factors of the muffler capability at that frequency. After the investigation in steps S1 to S6 above, the cause of insufficient transmission loss at that frequency can usually be found. Therefore, the method is not set to no in step S6.

[0053] A silencer is a device that allows airflow to pass through and attenuates noise. Based on the principle of noise reduction, it can be divided into resistive silencers and reactive silencers.

[0054] Among them, resistive silencers can also be described as a type of absorption silencer. Their structure involves filling the pipe with sound-absorbing material, allowing the airflow to come into contact with the sound-absorbing material. In this way, sound waves propagate in the sound-absorbing material, causing the air in the pores of the sound-absorbing material and the fine fibers in the sound-absorbing material to vibrate, converting sound energy into heat energy, thereby achieving the purpose of noise reduction.

[0055] The transmission loss of a resistive muffler can be approximated using the following formula from the prior art:

[0056]

[0057] In the formula, ΔL is the transmission loss in dB; P is the perimeter of the channel cross-section in meters; and S is the area of ​​the channel cross-section in square meters. 2 l represents the effective length of the muffler, in meters. The noise reduction coefficient is related to the sound absorption coefficient of the resistive material.

[0058] It is evident that the transmission loss of a resistive muffler is related to the muffler's structural form, length, channel cross-sectional area, sound absorption coefficient, and thickness of the sound-absorbing material.

[0059] Reactive silencers utilize abrupt changes in the cross-section of a pipe or a bypass resonant cavity to cause sound waves propagating along the pipe to be reflected and interfered at the abrupt cross-section, thereby achieving noise reduction. Reactive silencers have excellent mid- and low-frequency noise reduction characteristics. Commonly used reactive silencers include expansion chamber silencers and resonant cavity silencers.

[0060] The transmission loss of a resonant cavity reactive silencer can be calculated using the following formula from the prior art:

[0061]

[0062] In the formula, ΔL is the transmission loss in dB; d is the diameter of the perforation; and S is the cross-sectional area of ​​the channel in m². 2 f represents the sound wave frequency, measured in Hz.

[0063] f0 is the natural frequency of the resonant cavity silencer, in Hz, and can be calculated using the following formula in the prior art:

[0064]

[0065] In the formula, C is the speed of sound, in m / s; S0 is the cross-sectional area of ​​the perforation, in m². 2 V represents the volume of the resonant cavity, in meters (m³). 3 L K The effective length of the neck, in meters (m), L K =l+l k Where l is the neck length of the hole, and if it is a perforated plate, l is the plate thickness. k It is a correction factor; for a circular hole with a neck diameter of d, l k =0.8d.

[0066] It is evident that the transmission loss of a resistive muffler is related to the muffler's structural form, length, channel cross-sectional area, as well as the thickness, pore diameter, and perforation rate of the perforated plate.

[0067] In a specific embodiment, a schematic diagram of a certain vehicle's exhaust muffler is shown below. Figure 2 and Figure 3 As shown.

[0068] like Figure 4 The figure shows the transmission loss curve of the exhaust muffler of this model. It can be seen that the transmission loss is the smallest near 220Hz, which is only 18dB. This does not meet the design requirement of more than 20dB, resulting in a noise peak near 220Hz at the left ear of the right rear seat in the vehicle when idling.

[0069] To solve the above problems, the exhaust muffler needs to be optimized. Hypermesh and Virtual Lab (or GT Power) software should be used to conduct CAE analysis and troubleshoot the reasons for insufficient transmission loss at this frequency, followed by rectification and verification on a real vehicle. Details are as follows:

[0070] Step 1: Model the exhaust muffler using software. If the muffler is a resistive muffler, first adjust the thickness or silencing coefficient of the resistive material on the intake or exhaust inner pipe. The silencing effect of a resistive muffler is related to its silencing coefficient; the larger the silencing coefficient, the greater the silencing effect. At a certain frequency, increasing the thickness of the resistive material can improve the sound absorption effect of mid-to-low frequency sound waves, but has no effect on high frequency sound waves. In engineering applications, thinner sound-absorbing materials are used to absorb high-frequency sound waves, typically 3-5 cm thick; thicker sound-absorbing materials are used for low-frequency sound waves, typically 5-10 cm thick. After adjustment, perform CAE analysis to obtain the transmission loss curve. Observe whether the transmission loss increases near 220 Hz. If it does, the reason for insufficient transmission loss at this frequency is the thickness of the resistive material. Adjusting the thickness of the resistive material to a suitable value will make the transmission loss at 220 Hz meet the requirements. If not, i.e., there is no improvement, proceed to Step 2. If the muffler is a reactive muffler, proceed directly to step 2 for cavity disassembly and analysis.

[0071] Step 2: Remove the resistive material from the inlet and outlet pipes, then disassemble each chamber of the exhaust muffler and calculate the transmission loss for each chamber to find the cause of the transmission loss not meeting the requirements at 220Hz. Figure 5 As shown, it is divided into four chambers: chamber 21, chamber 22, chamber 23, and chamber 24. If the transmission loss of a certain chamber at 220Hz matches the lowest transmission loss of the exhaust muffler near 220Hz, then the factors affecting the insufficient transmission loss of the exhaust muffler (i.e., insufficient noise reduction capacity) are the length and volume of that chamber. Simply adjusting the length and volume of that chamber to appropriate values ​​will ensure that the transmission loss at 220Hz meets the requirements. If the transmission loss of each chamber at 220Hz does not fail to meet the requirements, proceed to step 3 for analysis and troubleshooting.

[0072] Step 3: For the exhaust muffler, the frequency corresponding to the maximum transmission loss decreases as the length of the inner tube increases. Adjust the lengths of the intake inner tube 11, the exhaust inner tube 12, and the transverse inner tube 15. If the minimum transmission loss is to the left of the peak (i.e., maximum) transmission loss, extend the length of the inner tube; otherwise, shorten it. The adjustment interval is generally 200mm. Then perform CAE analysis. After adjustment, if the peak (i.e., maximum) transmission loss moves towards (i.e., closer to) the original minimum transmission loss point of the exhaust muffler, the influencing factor is the length of the inner tube. Adjusting the length of the inner tube to a suitable value will ensure that the transmission loss at 220Hz meets the requirements. If not, proceed to Step 4 for analysis and troubleshooting. Figure 6As shown, after CAE analysis, the peak value near 220Hz on the transmission loss curve after the length of the exhaust inner tube was extended did not shift to the position close to 220Hz. In other words, the transmission loss near 220Hz is still low and there is no improvement. The dashed line in the figure shows the transmission loss curve after the exhaust inner tube was extended, and the solid line shows the original transmission loss curve of the exhaust muffler.

[0073] Step 4: Since the transmission loss and frequency of the exhaust muffler are related to the diameter and number (or perforation rate) of the perforations 14 on the inlet and outlet pipes and the baffle 13, adjust the diameter and number of perforations on a certain pipe or baffle. After each adjustment, increase or decrease the diameter or number of perforations by 30% or 50%, perform CAE analysis. If, after adjustment, the point of lowest transmission loss shifts away from 220Hz, the influencing factor is the diameter or number of perforations on that pipe or baffle. In this case, adjusting the diameter or number of perforations on that pipe or baffle to a suitable value will ensure that the transmission loss at 220Hz meets the requirements. If not, proceed to Step 5 for analysis and troubleshooting.

[0074] Currently, the intake manifold has a perforation diameter of 8mm, 38 holes, and a perforation rate of approximately 38%. The number and arrangement of the perforations are adjusted to 20, resulting in a perforation rate of 25%. Simulation analysis reveals that the peak at 860Hz disappears, but the lower transmission loss at 220Hz does not shift. This indicates that adjusting the number of perforations does not improve the transmission loss at 220Hz.

[0075] Step 5: Adjust the cross-sectional shape of the entire exhaust muffler housing, for example, changing it from an elliptical shape to a circular shape. After adjustment, perform CAE analysis. If the transmission loss at 220Hz increases, then the cross-sectional shape of the exhaust muffler is the influencing factor on the muffler's noise reduction capability. Continue adjusting this cross-sectional shape until the transmission loss at 220Hz meets the requirements. Figure 7 As shown, after adjusting the cross-sectional shape of the exhaust muffler, the transmission loss near 220Hz is significantly increased, while the transmission loss at other frequencies does not change much. The dashed line in the figure shows the transmission loss curve after the cross-sectional shape of the exhaust muffler is adjusted, and the solid line shows the original transmission loss curve of the exhaust muffler. Figure 4 and Figure 6 as well as Figure 7 The horizontal axis represents frequency, and the vertical axis represents transmission loss. This confirms that the noise at 220Hz is caused by the cross-sectional shape of the exhaust muffler.

[0076] Step 6: Adjust the parameters on the exhaust muffler model (i.e., the adjustment items in the above steps), and then perform CAE simulation analysis to find the reason why the transmission loss at 220Hz does not meet the requirements. Then, optimize and improve the exhaust muffler entity accordingly and test it on the vehicle. After testing, after installing the optimized exhaust muffler, the noise at the left ear of the right rear seat in the car at idle speed N gear decreased by 1.2dB(A), and the noise peak at 250Hz decreased by 4.4dB(A).

[0077] The exhaust muffler optimization method of the present invention, through preliminary simulation analysis, can systematically, quickly and effectively find the cause of insufficient transmission loss of the exhaust muffler at a certain frequency and improve it, thereby improving the noise reduction capability of the exhaust muffler, enhancing the NVH performance of the whole vehicle, and improving the driving comfort of the vehicle.

[0078] The above are merely preferred embodiments of the present invention. It should be noted that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Moreover, after reading the contents of the present invention, those skilled in the art can make various modifications or alterations to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for optimizing an exhaust muffler, characterized in that, It includes the following steps: Step S1: When the transmission loss of the exhaust muffler at a certain frequency is less than the design requirement, determine whether the exhaust muffler is a resistive muffler. If yes, proceed to step S2; if no, proceed to step S3. Step S2: In the exhaust muffler model, adjust the thickness or noise reduction coefficient of the resistive material on the intake inner pipe and the exhaust inner pipe of the exhaust muffler. After adjustment, simulate and analyze whether the transmission loss at this frequency is greater than the design requirement. If yes, proceed to step S7; otherwise, proceed to step S3. Step S3: Remove the resistive material from the intake and exhaust pipes, then disassemble each chamber of the exhaust muffler and calculate the transmission loss of each chamber. If the transmission loss of a certain chamber at a certain frequency is less than the design requirement, adjust the length and volume of the chamber and then proceed to step S7; otherwise, proceed to step S4. Step S4: Adjust the length of the intake or exhaust pipe. After adjustment, perform simulation analysis to confirm whether the transmission loss at that frequency is greater than the design requirement. If yes, proceed to step S7; otherwise, proceed to step S5. Step S5: Adjust the diameter and number of holes in the intake or exhaust pipe or partition. After adjustment, perform simulation analysis to confirm whether the transmission loss at this frequency is greater than the design requirement. If yes, proceed to step S7; otherwise, proceed to step S6. Step S6: Adjust the cross-sectional shape of the exhaust muffler, and perform simulation analysis after adjustment to confirm whether the transmission loss at this frequency is greater than the design requirement. If so, proceed to step S7. Step S7: Based on the adjustments, make corresponding modifications to the exhaust muffler, and then install it on the vehicle for testing and verification.

2. The exhaust muffler optimization method according to claim 1, characterized in that, In step S4, after adjusting the length of the intake or exhaust inner tube, if the minimum value of the transmission loss on the transmission loss curve obtained from the simulation analysis is to the left of the maximum value of the transmission loss, then the length of the inner tube is extended; otherwise, the length of the inner tube is shortened. Then, the length of the inner tube is adjusted again, and simulation analysis is performed. If the maximum value of the transmission loss is closer to the minimum value of the transmission loss compared to before the adjustment, then it is determined that the length of the inner tube affects the noise reduction capability and needs to be improved; otherwise, proceed to step S5.

3. The exhaust muffler optimization method according to claim 2, characterized in that, When adjusting the length of the intake or exhaust inner tube, the interval for each adjustment should be between 150mm and 250mm.

4. The exhaust muffler optimization method according to claim 3, characterized in that, The length adjustment interval is 200mm.

5. The exhaust muffler optimization method according to claim 1, characterized in that, When adjusting the length of the intake or exhaust inner tube, adjust the length of the exhaust inner tube first, and then adjust the length of the intake inner tube.

6. The exhaust muffler optimization method according to claim 1, characterized in that, In step S5, after adjusting the diameter and number of perforations in the intake or exhaust pipe or partition, if the simulation analysis results show that the minimum transmission loss of the exhaust muffler is not at that frequency compared to before the adjustment, then the influencing factor of the muffler capacity is determined to be the diameter and number of perforations in the pipe or partition, and the diameter and number of perforations in the pipe or partition are adjusted. Otherwise, proceed to step S6.

7. The exhaust muffler optimization method according to claim 1, characterized in that, In step S5, during adjustment, the diameter of the perforation is increased or decreased by 30% or 50% each time.

8. The exhaust muffler optimization method according to claim 1, characterized in that, In step S5, during adjustment, the number of perforations is increased or decreased by 30% or 50% each time.

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