With 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 noise. It is seriously polluting the urban environment, affecting people's 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, thereby 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 the 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 three 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 installation 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 become a key automotive noise control.
In addition, automobile tires at high speed, it will also cause more noise. This is because of the tire at the ground flows, the pattern is located in the air by ground tank and re-extrusion process caused by inhaling gas pump sound, as well as tread patterns with percussive sound of the road.
2 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. Japan's laws and regulations, small car in the next decade 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, light trucks for 83.5dBA. This shows that our country in the vehicle noise control will have to make do.
3 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. Subjective 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 technology in the finite element method (FEM) and boundary element method (BEM) has been widely applied.
4 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, are 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 transformation 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 vibration and noise reduction level of power, economy, reliability and strength, stiffness, quality, manufacturing costs and use are closely related.
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