1 Introduction
In the early days of the invention of the automobile, because the power of the engine is relatively low, basically it is low-speed driving, and its vibration and noise problems are not obvious, however, with the development of science and technology and social progress, the engine power continues to increase, and the emergence of highways has promoted the rapid increase of vehicle speed, which has led to the increasing prominence of vehicle noise problems. Vehicle noise will not only cause environmental pollution, but also affect the driver's concentration and vehicle safety, and even cause harm to the spirit and physiology of the people in the car.
Therefore, most customers in the purchase of cars are hoping that the driving environment of the car is quiet, riding up is smooth, can enjoy the fun of driving, for this reason, the vibration and noise performance of the car is particularly important. Statistical results show that the vibration and noise performance of the car and the customer's overall impression of the car evaluation is directly related, in addition to the pursuit of traditional low noise and vibration, the requirements for sound quality are also getting higher and higher, so the car's NVH (Noise, Vibration & Harness) performance, that is, noise, vibration and harshness performance has become a hot spot in the current research.
In order to control the noise pollution generated by vehicles, countries have successively introduced relevant environmental protection regulations and standards to strictly limit the noise generated by vehicles. China in 1979 introduced the motor vehicle noise allowable standard GB1495-1979, in 2002 on the basis of the "motor vehicle allowable noise" and promulgated GB1495-2002 "car acceleration outside the noise limit and measurement method", compared with the previously promulgated GB1495-1979, GB1495-2002 to make up for some defects of GB1495-1979, the measurement site should be met by specific provisions of the acoustic conditions. However, GB1495-2002 is only equivalent to the ECE R51/02 "Vehicle Acceleration Noise Limit" issued by the Economic Commission of Europe in 1997, and in 2007, the Economic Commission for Europe has formulated a new version of the test method for motor vehicle noise, referred to as ECE R51/03 [4], which is more stringent than ECE R51/02.
It can be seen that there is a big gap between The domestic and developed countries in the formulation and implementation of motor vehicle noise regulations, vehicle noise and vibration problems need to be further strengthened, and the design level of automobiles also needs to be improved. Compared with some well-known foreign automobile companies, such as Volkswagen of Germany, Toyota of Japan, and General Motors of the United States, there are still large differences in the research of vehicle NVH performance of domestic automobile manufacturers, and the research is not in-depth enough, which has also become an important factor restricting the development of domestic automobiles. Cars are usually composed of engines, chassis, electrical equipment and body systems, and the load-bearing car body system is the direct carrier of the occupants of the car, mainly composed of sheet metal parts, its design should consider both the safety of the car, but also consider the riding space, air resistance and appearance and other issues, and the body vibration characteristics and noise characteristics in the car also directly affect the passenger's riding comfort. In view of the noise problem in the vehicle riding room, study its generation mechanism, explore the way of noise generation in the car and take some methods to control, for example, through structural modification, laying damping layer, additional quality and other control panel vibration radiation noise, is conducive to improving the acoustic characteristics of the car, to improve the market competitiveness of the car is of great significance.
2 Automotive NVH Overview
Automotive NVH definition
Automotive NVH refers to the noise (noise), Vibration (vibration) and Harshness (comfort) of the car, mainly to study the impact of car noise and vibration on the performance and comfort of the whole vehicle.
Noise is a sound that causes irritability or is too loud to endanger human health. Car noise not only increases the fatigue of drivers and occupants, but also affects the driving safety of cars, increases environmental noise, is the main source of urban noise, and the noise in the car will affect the language communication between occupants. Noise is commonly used for sound pressure level evaluation, and its frequency range is 20-10kHz. Automotive noise includes structured noise (noise generated by body wall panel vibration), radiated noise (such as engine, exhaust system, brakes, etc.) and aerodynamic noise (wind noise, noise formed by air friction body) and so on.
Vibration is the cause of noise, therefore, the study of vibration and noise is inseparable. Vibration is often described by parameters such as acceleration, speed, and displacement, and its study frequency range is roughly 0.5-50OHz. Automobile vibration mainly includes body vertical vibration caused by uneven road surface, body vibration caused by unbalanced reciprocating inertia force of the engine, oscillation of steering wheels and torsional swing of the transmission train, etc., as well as vibrations such as steering wheels and instrument panels, and its frequency range is 1-80Hz.
Harshness refers to the quality of vibration and noise, it is not a physical concept juxtaposed with vibration and noise, but describes the subjective feelings of the human body about vibration and noise, which cannot be directly measured by objective measurement methods. Because acoustic harshness describes the uncomfortable sensation of vibration and noise, some have called harshness an unevenness or hazard. And because acoustic roughness is often used to describe the extremely uncomfortable transient response produced by impact excitation, some people call Harshness a shock characteristic.
In general, comfort describes the degree to which vibration and noise work together to make people feel tired.
Automotive NVH characteristics
Automotive NVH is reflected in the three aspects of noise, vibration and comfort, which appear simultaneously and are inseparable in the car, so they are often studied together. Automobile NVH characteristics refer to the changes in the subjective feelings of driver and occupant comfort under the action of vibration and noise in the car. It is a comprehensive expression of the human body's touch, hearing and visual sensations. Simply put, all the tactile and auditory sensations of the occupants in the car belong to the category of NVH research, in addition, including the strength and life of the car parts due to vibration. According to the NVH characteristics, the automotive NVH problem can be described by the following expressions 2-1 and Figure 2-1: source (excitation source) x transfer path (sensitivity) = response (receiver)
Fig. 2-1 Vehicle NVH diagram
Automobile NVH research is generally in accordance with the 2-1 expression, from the perspective of noise vibration comfort analysis of the mechanism of noise vibration inside and outside the car, that is, through the receiver (driver, crew) to find the incentive source of noise vibration, and then how the incentive source generates noise vibration mechanism and propagation path analysis and research, to find a way to reduce noise and vibration, to reduce the size of noise vibration inside and outside the car, and finally to improve the comfort of the car ride, so that it meets the requirements of customers and manufacturers. Since the excitation source is the fundamental cause affecting the performance of the vehicle NVH, knowing oneself and knowing the other, only by being familiar with its excitation source and the mechanism of generating noise and vibration can we find a way to reduce noise and vibration.
The main excitation sources affecting the performance of automobile NVH include engines, powertrains, tires and road surfaces, air, etc., and the vibration and noise they produce are transmitted to the body and interior through the action of transmitters such as suspension systems and body structure systems to form vibrations and acoustic responses. At different speeds, the main sources of noise and vibration are also different. Among them, the engine is the main source of noise and vibration when driving at low speed; when the car is driving at high speed, the friction and structural vibration of the tire and the road surface are the main source of noise and vibration; when the car is driving at high speed, the friction between the body and the air and the sound leakage become the most important noise source.
Here's a brief introduction to these incentive sources.
1. Engine
The engine is the heart of the car, the source of power. The engine generates power, pushes the drive shaft train, and then drives the wheels forward. The same engine is also the main source of noise and vibration in the car. The noise and vibration of the engine are composed of different order components, and the noise and vibration of the components associated with it are also related to the order, such as the noise of the air inlet in the intake system, the noise of the tailpipe in the exhaust system, and the transmission of vibration in the engine suspension system. In addition, the noise in the car, the vibration on the floor, the vibration on the steering wheel, etc. are also related to the order of the engine. The periodicity of the engine combustion process and the reciprocating motion of some of the forced parts are the most important noise and vibration sources that constitute the automobile, of which there are three main types of engine noise: combustion noise, mechanical noise and aerodynamic noise. The total noise level of the engine is related to the type, speed, power, bore and other parameters of the engine.
(1) Combustion noise is generated in the engine cylinder, the mixture is burned in the cylinder, and the gas pressure generated in the cylinder directly stimulates the engine structure, causing structural vibration, and is transmitted to the engine surface through external and internal propagation channels, and the air noise is formed by the radiation on the engine surface. It can be seen that the combustion noise is caused by changes in the pressure of the gas in the cylinder, which includes the dynamic load caused by a sharp change in the pressure in the cylinder, and the high-frequency vibration of the gas caused by the shock wave. The intensity of the noise caused by the gas-powered load depends on the pressure growth rate and the duration of the maximum pressure growth rate. The magnitude of the combustion noise is not only related to the cylinder pressure spectrum, but also to the structural attenuation characteristics of the engine, because the noise is generated by vibration, and the vibration depends on the excitation characteristics and the structural response characteristics of the vibration system. The difference between the cylinder pressure level and the engine's noise sound pressure level is called the attenuation amount. sex. The large structural attenuation, the noise is small.
(2) Mechanical noise refers to the noise of shock and vibration of moving parts under the action of gas pressure and inertia force, mainly piston knocking noise, gear meshing noise, oil supply system noise, gas distribution mechanism noise, timing system noise, auxiliary system noise, unbalanced inertia force caused by body vibration and noise and bearing noise. Mechanical noise increases with the increase of rotational speed and propagates outward through the body. After the engine aerodynamic noise is effectively controlled, mechanical noise running at high speed is often the main source of noise.
(3) Aerodynamic noise is the noise generated by the flow of gases (such as periodic intake and exhaust) or the movement of objects in the air, the collision of air with objects, and the eddy currents generated by the air; or the disturbance and expansion caused by the sudden pressure of the air (such as the injection of high-pressure gases into the air).
2. Powertrain
The vibration sources of the power transmission system mainly include: gearbox, transfer agent, transmission shaft, drive axle, half shaft and cardan joint.
There are many gears in the gearbox, and through the meshing between different gears, the drive shaft rotates at different speeds, so that the speed of the wheel changes. It is not possible for these gears to mesh perfectly, and as a result, vibrations are generated. Also in the interior of the transaxle and in the transferor, the transmission and distribution of power is also carried out by gear meshing, and the same gear meshing is not good enough to produce vibration. Drive shafts and transferrs are rotating moving parts that generate centrifugal forces when the centroid of the shaft system does not coincide with the centerline of rotation, and these additional centrifugal forces transmit vibrations to the body. In addition, the system consists of a whole from the gearbox to the half shaft, and when the bending and torsion frequencies of this system are consistent with the excitation frequency of the engine, the system will resonate. When the shaft system is connected with a cross-axis rigid universal node, a second-order vibration is generated due to the uneven angle of the passive shaft.
The noise sources of the powertrain are: transmission, transferper, transaxle and drive shaft. Due to their vibrations, they all produce noisy sounds. In addition, the drive shaft can also emit noise during operation. The drivetrain is connected to the body through bearings and isolators, so the vibrations generated by these excitation sources are transmitted through these bearings and isolators to the cabin, creating vibrations and acoustic responses. The noise felt in the car mainly includes: boom caused by the rotation step of the drive shaft system, moaning sound related to the engine ignition step, single-frequency noise caused by gear meshing, and some collision noise. The vibrations felt in the car mainly include: the vibration of the bottom plate in the car, the vibration of the steering wheel and the vibration of the seat.
3. Road surface and tires
Road excitation is transmitted to the suspension through the tires and axles, and to the body through the suspension system, causing the body to vibrate and acoustically respond. At the same time, the friction between tires and road surfaces will cause tire noise, and when the car travels at a speed of more than 50km/h, tire noise becomes the main component of driving vehicle noise. When engine noise decreases, tire noise becomes a major source of noise. The impact of different types of road surfaces on tire noise is different, and technicians analyze the impact of road conditions on the tire noise of a certain model through comparative tests on the relationship between different road surfaces and tire noise as shown in Table 2-1. The unevenness of the same kind of road surface is different on the noise vibration of the whole vehicle is also different, and the noise vibration generated by the road surface with a small unevenness coefficient is small, on the contrary, it is large. Table 2-1 The impact of tire noise on different roads facing the same model
4. Air
Wind excitation generally produces wind noise, which is the main noise encountered by the car when driving at high speed, wind noise is an aerodynamic noise, the car moves relatively with the air flow when driving, and the air flow disturbance acts throughout the car, directly or indirectly affecting the noise in the car. When the car is driving at low speed, the noise in the car mainly comes from the engine and road tire noise, and the wind noise component is small, but when the driving speed exceeds 80km/h, the wind noise gradually dominates. Application of automotive NVH characteristics research Automotive NVH test research plays an important role in both new model development and performance improvement of existing models.
The study of the characteristics of the automobile NVH is not only reflected in the development process of new models, but also in the improved design of existing models. 1, the application of the new model development process In the development of new models, the research of automobile NVH characteristics can be regarded as a design method based on computer simulation analysis as a design goal of automobile NVH characteristics. In the process of vehicle research and development, NVH performance research can be divided into the following four stages:
(1) Investigate and determine the vehicle target
Develop NVH standards for newly developed models through research on government regulations, consumer requirements, and NVH performance levels of competing models. At this stage, through the review of government regulations, the new model consumer market questionnaire survey, and the NVH performance target value test of the competing models, the NVH performance target data of the new model to be designed are obtained, so as to formulate the NVH target value of the new model based on these data.
(2) Vehicle simulation analysis and matching subsystem targets
The performance target value of each subsystem is determined according to the NVH performance target value of the vehicle. Subsystems generally include engines, suspension systems, powertrain mounting systems, bodywork, seats and steering systems. For example, the vibration generated between the vehicle and the road surface is transmitted to the body wall panel through the suspension system, causing the wall panel to vibrate and thus forming the noise inside the car. In this process, the body structure and indoor cavity can be described by mathematical models, that is, simulation studies can be carried out by establishing a CAE model of the whole vehicle. Through CAE simulation, the actual road characteristics of the structure can be linked to the subsystem parameters (such as suspension stiffness, etc.), so that the target value of each component can be determined according to the NVH performance target value of the vehicle, but it should be noted that the target value of each subsystem should meet the design goals and experimental requirements.
(3) Achieve the performance goals of the subsystem and the vehicle through the structural design of the components The following work must be completed here: First, determine the detailed characteristics of each component, which may not be expressed in the previous modeling analysis, such as connection holes, processes, solder joint positions, etc. Second, the reliability design and multi-objective optimization design of each subsystem component are carried out to improve the NVH characteristics of the car to ensure that the design scheme of the structural components is optimal. Third, the design model conditions (such as limit size, etc.) must be met, and the verification of the limit conditions (such as suspension impact) must be carried out.
(4) Test and adjustment of the sample car After the production of the sample car, the real car test can be carried out, the test is generally carried out in the laboratory or on the road, and the NVH target value of the vehicle is tested by the acceleration sensor, microphone, etc., so as to make the necessary adjustments and modifications according to the difference between the performance of the test product and the design goal.
2. Application in the process of NVH performance improvement of existing models
(1) Test the unknown and abnormal noise and vibration of the vehicle proposed by the user, and give certain subjective and objective evaluation results. These tasks require the mastery and correct use of measuring methods and measuring instruments.
(2) According to the test results of step (1), after a preliminary understanding of the existing noise and vibration problems, the noise vibration source identification, noise vibration source transmission path analysis and other test schemes are formulated, and the test analysis is carried out, and the test results of the analysis can be compared with the results of CAE simulation calculation, so that the fault diagnosis and the identification of noise and vibration sources are more accurate.
(3) According to the results of test analysis, effective engineering governance, the implementation of noise reduction and vibration reduction, to meet the requirements of customers. The basic method of achieving noise reduction and vibration reduction:
A. Eliminate the root cause of vibration and noise. This involves modifying the structure of components that generate vibration noise, for example, improving their vibration characteristics and avoiding resonance;
B. Cut off the path of vibration and noise transmission. It involves the analysis and improvement of the vibration transmission characteristics of the structure so that it has a significant attenuation effect on the vibration noise rather than amplification.
3. Development of automotive NVH
In the traditional sense of noise control is to reduce the size of the sound, only considering the size and frequency components of the sound level, after the 1980s, the automotive industry began to use sound quality, sound quality-led NVH development, such as the sound of the engine, the tone composition of the jet aircraft or the acoustic performance of the electric shaver, all reflect a certain aspect of sound quality. The perception of the sound quality of a product is an important factor in characterizing its characteristics. Sound quality is no longer limited to noise reduction, shaping the right product sound is a complex task, and the product development process involves multiple steps and tools. The complete definition of sound quality, which is widely recognized by the international academic community, was first given by BLAUER: "Sound quality is the suitability of sound in the connotation of a specific technical goal or task, and the "sound" defined in sound quality does not refer to a physical event such as sound waves, but is a subjective judgment made by the human ear for the auditory perception process of sound events and ultimately made." "The sound quality problem in the automotive industry has been from the initial research on the main components of the vehicle, the engine, etc., into the research of all aspects of various components, the future development of the car environmental protection, safety, comfort, low cost is the main line, and the NVH performance in these main lines occupies a large proportion." Statistics show that about one-third of the failure problems of the whole vehicle are related to the NVH problem of the vehicle. Good NVH matching not only achieves good kinetic properties but also saves production costs.
In the 1960s and 1970s, the major Western automobile companies began to pay attention to the NVH problem of automobiles, China's NVH research started late, independent brands have developed to the present only more than 10 years, from the perspective of international NVH level, Japan has done the best in this regard, the United States is also good, followed by Europe. Governments in the NVH regulations, there are no too strict regulations, mostly from the increasingly demanding requirements of customers for vehicle performance, European regulations require cars to pass through noise less than 74DB, China M2 diesel engine is 77DB, RM1 class diesel locomotive is 75DB. Good NVH characteristics can improve the risk of early failure of automotive components due to vibration and improve the reliability of components.
Compared with foreign countries, there is a certain gap in China's NVH level. For example, the noise value of vehicle idling when the air conditioner is turned on, the vehicle in Japan and North America is 43-45DB, while the local vehicle in China often reaches 50DB. The noise value of a domestic light bus is shown in Figure 3-1, and the noise value of several cars is shown in Figure 3-2.
The NVH capabilities of domestic enterprises have reached a certain level, such as Shanghai GM/Pan-Asia Automotive Technology Center, which has certain development capabilities, and the NVH work of the rest of the joint ventures in China is mainly physical test certification; while most of the domestic independent brands are in the stage of prototype test improvement (usually cooperating with foreign test consulting companies), and the CAE capability and its integration with the test still need to be strengthened.
The current status of other enterprises is as follows:
(1) SAIC Tongji Noise and Vibration Engineering Center, Tongji University Automotive College NVH laboratory hardware first-class, and relatively complete, its anechoic chamber (with low noise hub) is the largest in the Far East, reaching 1200m3, reverberation chamber is 268m3, test system is LMS and other main flow equipment;
(2) Chery's conventional NVH test engineering and research cooperate with the noise and vibration laboratory of Hefei University of Technology, and the NVH performance improvement of some products is mainly completed through cooperation with foreign test consulting companies. For example, through cooperation with the Italian Prototipo Experimental Company, a number of small projects in the NVH of models such as the Son of the Orient and the New Flag Cloud have been improved, which has greatly improved the level of technical personnel while enhancing the competitiveness of the products. Chery has 4 sets of LMS vibration and noise test system and other mainstream equipment, set up an NVH department, CAE has a special NVH analyst;
(3) FAW's NVH testing capability has been established for a long time. Among them, the noise test room is built according to international standards, including: vehicle noise test room, powertrain noise test room. Among them, the vehicle noise test room is a semi-anechoic chamber, which can carry out the outer and inner noise tests of various types of cars, light vehicles, medium-sized trucks, vans, buses and other models, and the powertrain noise test can also be carried out for the engine with a maximum power of 200KW, a maximum torque of 400 Nm and a maximum speed of 7500 r/min; the vibration noise test of its powertrain can also be carried out;
(4) The NVH of the second automobile started earlier, and there is a special NVH research organization, and its anechoic chamber is 6.8m*5.2m*6m, and the reverberation chamber is 5.6m*6.7m*5.8m. As early as 1996-1998, Ye Zhigang led his team to do a relatively in-depth study on the "analysis and control of passenger car noise test research", and its results were applied in the development of passenger car products of Dongfeng Motor Company, which solved the problem of large noise in passenger cars and achieved good results. The project creatively applied the structure sound sensitivity function in the body structure analysis and control to better solve the influence of engine suspension on the noise in the car, and later won the 2001 China Automotive Industry Science and Technology Progress Award;
(5) Chongqing Changan mainly cooperates with Lande Technology, and in 2006, a new vehicle anechoic chamber was established, and the test system was also used in the mainstream equipment of the industry such as Head Acoustic;
(6) Futian was built by The German Fiast to build an anechoic chamber for it, and the test system is equipped with a 32-channel LMS vibration mode analysis system, a 60-channel B&K pass noise test analysis system, and a 36-channel BBM noise source analysis and sound quality evaluation and analysis system;
(7) JAC has the ability of conventional NVH performance test and evaluation, and has 2 sets of vibration and noise test systems of mainstream manufacturers such as LMS; (8) Geely hardware has conventional vibration and noise test equipment, can complete the routine test work, its research institute also has a special person to engage in NVH CAE work, the preparation of large laboratories such as anechoic chamber has also begun the initial investigation, the improvement of product NVH performance is mainly through cooperation with foreign professional companies to achieve.
For example, in the process of design and development of King Kong, a professional team of SCS Technology Center of Alipalia Company, a professional automobile noise reduction company, was specially hired to carry out special NVH engineering processing. In recent years, NVH has not only been the focus of automakers, auto parts companies have also begun to pay attention to the development of NVH performance of parts, such as fast group specializing in the production of transmissions has built an industry-leading anechoic chamber, investing energy in the development of low-noise transmission products. Overall, the passenger car NVH is at the forefront, and commercial vehicles have also begun to establish their own NVH development team, equipped with mainstream noise vibration test systems and professional anechoic chambers and professional NVH engineering personnel.
4 Research methods for the NVH problem
The source of automobile noise mainly comes from engine, intake and exhaust systems, fan noise, transmission system, tire noise, brake noise, vehicle acoustic structure noise, and aerodynamic noise. The noise contribution of each assembly should be reasonably matched, and the characteristic research of NVH should be based on the whole vehicle as the research object, reasonably matching each system, and requiring the noise contribution of each subsystem to be minimized. Usually, the main theoretical methods for controlling automobile noise and vibration problems are finite element method, boundary element method, statistical energy method, and finite element method is applied to analyze the dynamic characteristics of the structure; The boundary element method is suitable for dealing with the radiation problem of noise; The statistical energy method is to divide a complex structural system or acoustic system into several coupled subsystems, each subsystem has several resonant frequencies in the corresponding frequency range, and establishes the relationship between the energy flow between each subsystem according to the various parameters of the system. At this stage, the application of computer simulation analysis technology (CAE) in the design and development of automotive products has been quite common, which greatly facilitates the understanding and grasp of the design mechanism of the engineer, improves the efficiency of design and development, and promotes the accelerated upgrading of products.
However, the confidence level of CAE analysis is a "bottleneck" issue, and the confidence of the simulation analysis is difficult to guarantee for the NVH performance of vehicles with highly complex mechanisms and models. In order to solve this "bottleneck", the common practice is to combine CAE technology with experimental testing, and determine the effectiveness of simulation by comparing the coincidence of simulation and test results. However, for the test process, conditions and on the other hand, the current application field has emerged a variety of CAE software systems that support NVH simulation analysis, such as ADAMS, SYSNOISE, AUTOSEA, LMS, etc. Software systems based on different kernel technologies have different scopes of application for dealing with problems. In order to ensure the confidence of the simulation analysis, software tools should be reasonably selected taking into account the characteristics of the specific problem. For example, the acoustic-vibration coupling finite element technology is mainly suitable for the low frequency range, and is an effective tool for analyzing the low-frequency structured radiated noise (Booming) in the car; The statistical energy law is more suitable for mid- and high-frequency noise analysis with dense modalities, and so on. It is worth noting that in order to improve the basic data conditions necessary for simulation and analysis, the foreign automotive engineering community has made unremitting efforts. An in-vehicle noise database system has been established to cover the typical driving conditions of 15 models, effectively supporting the simulation analysis process and helping to ensure its confidence.
5 Automotive NVH control and improvement measures
Noise control mainly has two aspects: active measures and passive measures: active measures require reducing noise from the source of noise, such as improving the structure of the machine, increasing the excitation frequency, reducing the low-speed noise of the engine, improving the processing accuracy and assembly quality of parts, reducing motion noise, improving the suspension system of the components, blocking vibration transmission, improving the body structure, improving the stiffness, improving the first-order mode, reducing the number of local modes, etc.; Passive measures require good sound absorption, vibration absorption, sealing, sound insulation, vibration isolation, and damping materials. So far, damping, sound-absorbing materials and structures have been widely used in the field of automotive noise control, such as: damping coatings, foam materials, restraint layer damping structures, interior sound-absorbing surfaces, and the recent appearance of ABA insulation wall liners, etc. These have become the most important engineering treatment methods for improving the NVH performance of vehicles.
6 Conclusion
For a long time, major developed countries have attached great importance to the problem of automobile noise control, and have accumulated rich theoretical and technical research results and engineering practical experience in solving problems. However, due to the complexity of the problem, there are still a large number of theoretical and technological gaps in the field, many of which are worldwide problems. The domestic automobile industry should fully grasp this opportunity, and while following and learning from foreign advanced technologies to form a "latecomer advantage," it should strive to make breakthroughs in some aspects in a short period of time through independent innovation, so as to promote the overall leapfrog development of automobile noise control technology.