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1、Ways to reduce vehicle noiseWith the rapid development of automobile industry, there is comfort and vehicle vibration and noise control of more and more stringent requirements. According to relevant data shows that 70 percent of the city noise from the traffic noise, and traffic noise is mainly car
2、noise. It is seriously polluting the urban environment, affecting peoples life, work and health. So noise control is not only related to comfort, but also related to environmental protection. However, all also from the vibration noise, vibration can cause certain parts of the early fatigue damage, t
3、hereby reducing the service life of motor vehicles; excessive noise can damage hearing the driver will enable the rapid driver fatigue, thus driving security constitutes a grave threat. So noise control, is also related to motor vehicle durability and safety. Thus vibration, noise and comfort are th
4、e three closely related, it is necessary to reduce vibration, reduce noise, but also improve ride comfort, and ensure the product economy, vehicle noise control in the standard range. One type of noise arising from car noise are the main factors of air power, mechanical drive, the electromagnetic th
5、ree parts. From the structure can be divided into the engine (ie, combustion noise), the chassis noise (ie, power train noise, all components connected with the noise), electrical equipment, noise (cooling fan noise, car noise generator), body noise (such as body structure, shape and attachment inst
6、allation unreasonable noise). One of the engine noise accounted for more than half of motor vehicle noise, including noise and body intake noise (such as engine vibration, the rotational axis Valve, Jin, door switches, such as exhaust noise). Therefore the engine vibration, noise reduction has becom
7、e a key automotive noise control. noise requirements of regulations in Europe, from October 1996 onwards, the external bus 77dBA noise must be reduced to 74dBA, noise was reduced by half energy, the end of the century further reduced to 71dBA. Japans laws and regulations, small car in the next decad
8、e to control noise standards at the following 76dBA. A number of domestic cities are also planning to traffic trunk lines in 2010 to control noise at the average of less than 70dBA. According to the domestic current data indicate that the domestic value of bus noise permit shall not exceed 82dBA, li
9、ght trucks for 83.5dBA. This shows that our country in the vehicle noise control will have to make do. noise assessment noise evaluation mainly refers to the car, outside noise and vibration adaptive value. Evaluation methods can be divided into subjective evaluation and objective evaluation. Subjec
10、tive assessment of the impact of vehicle noise is a major factor in comfort, loudness and uncertainties, such as semantic differential method can be used for subjective evaluation. At an objective evaluation, can be used PCNM noise measuring device for measuring test analysis; addition simulation te
11、chnology in the finite element method (FEM) and boundary element method (BEM) has been widely applied. noise control noise generation and dissemination in accordance with the mechanism of noise control technology can be put into the following three categories: First, the control of noise sources, ar
12、e two routes of transmission of noise control, noise three recipients are protected. One of the control of noise sources are the most fundamental, the most direct measures, including noise reduction to reduce the exciting force and the engine parts of the exciting force response, which means transfo
13、rmation of acoustic source local oscillator. However, it is difficult to control noise sources when necessary in the route of transmission of noise to take measures, such as sound absorption, sound insulation, noise reduction, vibration and vibration isolation measures. Motor vehicles and vehicle vi
14、bration and noise reduction level of power, economy, reliability and strength, stiffness, quality, manufacturing costs and use are closely related. engine to reduce vibration and noise of the engine noise is the focus of automotive noise control. Engine vibration and noise are generated at source. E
15、ngine noise is from fuel combustion, valve bodies, gears and piston timing noise percussion synthesis. (1) ontology engine noise Lower engine noise will be ontological transformation of local oscillator sound sources, including methods such as finite element method analysis and design engines, selec
16、tion of soft combustion process, improve the structure of the body stiffness, with the use of tight space, reduce noise cylinder cover. In addition, give the engine Tu damping material is an effective approach. Damping materials can kinetic energy into thermal energy. To deal with the principle of d
17、amping is a damping materials and components into its vibrational energy to consume. It has the following structure: Freedom damping layer structure, and spacing of freely damping layer structure, and constrained damping layer structure and spacing of constrained damping layer. It is clear that the
18、adoption of a decrease of resonance amplitude and accelerated the decay of free vibration, reducing the various parts of the Chuan-Zhen capacity, an increase of parts at or above the critical frequency of vibration isolation capacity. At present, some countries have designed an engine experts active
19、 vibration isolation system to reduce engine vibration, in order to achieve the purpose of noise reduction. (2) intake noise Engine intake noise is one of the main noise source, the Department of the engine noise of air power, with the engine speed increases to strengthen. Non-supercharged engine in
20、take noise major components, including the cyclical pressure fluctuation noise, vortex noise, the cylinder of the Helmholtz resonance noise. Diesel engine supercharger intake noise mainly from the turbocharger compressor. Two stroke engine noise from the Roots pump. In this regard, the most effectiv
21、e method is the use of intake muffler. There is a resistive type muffler (absorption type), resistant muffler (expansion type, resonance type, interference-type and porous decentralized) and the composite muffler. To combine with the air filter (that is in the air filter on an additional resonance c
22、hamber and sound-absorbing material, for example, type R3238) has become the most effective intake muffler, muffler volume of more than 20dBA. Chassis Noise (1) Department of exhaust noise Department of the chassis exhaust noise is the main noise sources, mainly from the exhaust pressure pulsation n
23、oise, air flow through the valve seat when issued by eddy current noise, because of boundary layer airflow disturbance caused by noise and exhaust Office jet noise composition. (2) power train noise Powertrain noise from the vibration caused by change gear meshing and rotating shaft vibration. Gener
24、al measures taken are: First, choose low-noise transmission, engine and gearbox are two and the main reducer, such as rear axle and chassis components for flexible rubber pad connections, so as to achieve the purpose of isolation; are three-axis rotational control balance degrees, to reduce torsiona
25、l vibration. Electric equipment noise (1) cooling fan noise Cooling fan noise happened devices are subject to wind retaining ring, water pump, radiator and transmission, but the noise generated depends primarily on the chassis. (2) automobile generator noise Automotive generator noise depends on the
26、 effects of a variety of sources, these sources have magnet source, mechanical and air power source. Noise level depends on the generator magnetic structure and ventilation systems, as well as generators precision manufacturing and assembly. Body Noise As the speed increased, the body will be more a
27、nd more noise, and air power are the main causes of noise. Therefore, the following programs to improve the body noise: First, to streamline the design of the body, achieve a smooth transition;second are in between the body and frame components to adopt a flexible connection; third， interior is soft
28、ened, such as Inner Mongolia at the roof and body skin the use of sound-absorbing material. In addition, the car at high speed when the tire is also a source of noise. Tire Tread greater, then the greater the noise. In addition, the tire tread with the noise generated also have a great relationship,
29、 there is a reasonable choice of the pattern of steel cord for radial tires to reduce tire noise are an effective way. Materials for the tire, the use of more flexible and soft rubber with high, you can create a low-noise tires. Other measures Automobile noise control, except in the design on the us
30、e of optimization methods and optimization of selected components, it can also carry out active control of noise. This is based on sound muffler technology, the principle is: the use of electronic muffler system with the opposite phase of the acoustic noise, vibration so that the two cancel each oth
31、er out in order to reduce the noise. This muffler device used extremely advanced electronic components, has excellent noise reduction effect can be used to reduce vehicle noise, engine noise, the engine could also be used to proactively support systems, to offset the engine vibration and noise.降低汽车噪
32、声的方法随着汽车工业的迅猛发展，对车辆的舒适性,缓震性和噪声有了越来越严格的要求。据有关资料显示，城市噪声的百分之七十交通噪声，交通噪声主要是汽车的噪音。这严重污染了城市的环境，影响人们的生活，工作和健康。因此，对噪声的控制，不仅关系到人类生活的舒适性，而且与环保有关。而且，所有的这些来自震动的噪声，无疑的还能够导致某些零件的早期疲劳损伤，从而减少了汽车的使用寿命；高分贝的噪声还会损害驾驶员的听觉使驾驶员在短时间内感到驾驶疲劳，这样就对安全驾驶就构成了严重的威胁。因此对噪声的控制，也与汽车的耐用性和安全性有关。因此振动，噪声和舒适性三方面是密切相关的，既要减少振动，降低噪音，而且还要提高乘坐舒
33、适性，保证产品经济性，使车辆的噪音控制在标准范围内。从汽车噪音产生的因素分产生噪声的原因主要空气阻力，机械传动和电磁三部分。从结构上可分为发动机（即燃烧噪声），底盘噪声（即动力传动噪音，与噪声有关的所有组件），电气设备，噪声（冷却风扇的噪音，汽车噪音发生器），车身噪音（如车身结构，形状和附件安装不合理的噪音）。发动机的噪音占汽车噪音的一半以上，包括发动机运行噪声和车身风口噪声（如发动机振动，曲轴转动，进，排气门，排气噪声）。因此发动机的振动，已成为汽车噪声控制降低噪音的一个关键因素。欧洲噪声法规要求从1996年10月起，巴士噪音必须由77dBA减少到74dBA，噪音制造能力减少一半，在本世纪末
34、进一步降低至71dBA。日本的法律和法规规定，在未来的10年小型车的噪音标准控制在76dBA以下。国内一些城市也计划在2010年交通干线的平均噪声控制在低于70dBA。国内目前的数据规定，巴士的噪音不得高于83.5dBA，轻卡的噪音不得高于82dBA。这是我国在车辆噪音控制方面的准则。对汽车噪音的评估与评价主要有，车外的噪音和缓振性。评价方法可分为主观评价和客观评价。对车辆的噪音的主观评价有舒适性，响度以及一些不确定因素，这些因素都可用于主观评价。在客观评价方面，可以用PCNM噪声测量计检测分析设备; 除了有限元法（FEM）和边界元法（BEM），仿真技术已广泛应用。根据噪声的产生和传播方法，可
35、以采取以下方法进行控制：噪声源的控制，有两种方法控制噪音的传播，起到保护噪音接收者的作用。对噪声源的控制是最根本，最直接的措施，包括降低噪音，减少振动影响力和振动的响应，这意味着声源转化为局部振荡器。但是，当噪声源的噪音开始传播时很难对其采取有效地控制，如吸音，隔音，减少噪音，振动和振动隔离措施。机动车辆和车辆的振动和噪音的降低水平，经济性，可靠性及强度，刚度，质量，生产成本和使用密切相关。汽车噪声控制的重点是减少发动机的振动和噪音。发动机振动和噪声产生的源头是燃料燃烧，阀体，齿轮，活塞敲击。（1） 发动机自身噪音降低发动机噪音，将发动机机体转变为本地振荡器的声源，包括诸如微分分析法和发动机的
36、设计，选择轻柔燃烧，提高发动机的刚度及改善并使用紧凑的空间结构，降低缸盖噪音。此外，给发动机涂阻尼材料是一种有效的方法。阻尼材料可将热能转化为动能。阻尼处理的方法是阻尼材料和其组成部分的振动能量消耗。它具有以下结构：自由阻尼层结构，间距和约束阻尼层结构和空间的约束阻尼层。显然，通过共振幅度减少和加快自由振动衰减，减少了各部分的传真能力，部分达到或超过临界频率的隔振能力增加。目前，一些国家的专家设计了发动机主动隔振系统，以减少发动机振动，以达到降噪的目的。（2） 进气噪音发动机进气噪声是主要噪声源之一，发动机受到的空气阻力，随着发动机转速的增加而增强。非增压发动机进气噪音的主要组成部分，包括周期
37、性压力波动噪声，涡流噪声，气缸的Helmholtz共振噪声。柴油机增压器噪声主要是涡轮增压器压缩机进气噪音。二冲程的Roots泵的发动机噪音。在这方面，最有效的方法是摄入消声器的使用。有一个电阻型消声器（吸收型），抗性消声器（膨胀型，共振型，干扰型和多孔分散）和复合消声器。要结合空气过滤器（即在空气过滤器的附加谐振腔和吸声材料，例如，R3238）已成为最有效的摄入量消声器，消声器的音量摄入量超过20dBA。机箱噪音（1） 排气系统噪声底盘的排气系统噪声是主要噪声源，主要由排气压力形成的脉动噪声，阀座气流由于边界层气流的干扰当涡流通过时发出的噪音和废气再循环喷气噪声组成。（2） 动力总成噪声动力
38、系统的噪音有齿轮啮合的变化所引起的振动和旋转轴振动。一般采取的措施是：第一，选择低噪声传输，发动机和变速箱是减低噪音的主要方面，如后轴和柔韧性很好的橡胶垫连接底盘部分，以达到缓震得目的；第二，三轴转动控制平衡度，以减少扭转震动。 电子设备的噪音（1） 风扇冷却噪音风扇冷却设备的噪声产生受风力保持环，水泵，散热器和传动装置的影响，但噪音的产生主要取决于底盘。（2） 汽车发电机噪声汽车发电机噪声的产生有多种原因，源头有磁场，机械和空气阻力。噪声水平取决于发电机磁场结构和通风系统，以及发电机的制造精密性和装配情况。车身噪声随着速度的增加，车身会产生越来越多的噪音，噪音的主要根源是空气阻力。降低车身噪
39、音主要有下面几种方法：第一，尽量是车身呈流线型，实现平稳过渡;第二，车身与框架组件采取平滑连接;第三，内饰的软化设计，如内蒙古，在屋顶和外墙合理利用吸音材料。此外，在高速时，汽车轮胎也是噪声源。胎面面积越大，产生的噪音也越大。另外，轮胎胎面与噪音也有很大关系，选择钢丝帘线的子午线轮胎可以有效地降低轮胎产生的噪音。用更柔韧橡胶作为轮胎原理，可以进一步降低轮胎产生的噪音。其他方法对汽车的噪声控制，除了优化设计方法和对所选组件的优化设计，还可以对噪声进行主动控制。这建立在对消声器技术的发展上，其原理是：在噪声和振动的对立阶段使用电子消声系统，是其相互抵消，以降低噪音。这种消声器设备用了非常先进的电子元件，具有良好的降噪效果，可以用来减少车辆噪音，发动机噪音，引擎也可以主动支持系统，以抵消发动机的振动和噪音。
