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The noise level and sound quality performance of a passenger vehicle are strongly dependent on the fluid-structure behavior that is the interaction between the air inside the cabin with its sheet metal structures. With the challenges of global platform vehicles and an increased ethanol usage as an alternative fuel, new approaches of product development and refinements become necessary in order to up-to-date standards of vehicle NVH (noise, vibration and harshness). By using a CAE model combined with experimental data, it was possible to predict the main noise and vibration propagation paths inside the vehicle, where some proposals could be handled in advance and then validated on vehicle. Several solutions may be found to solve issues that usually are delimited by technology, cost-benefit ratio, production ability, package restrictions and/or durability.

In NVH, the common sense is that quiet vehicles are vehicle which sources of noise are controlled. Transmission whine noise is an example of how is important to avoid unexpected noise coming from a specific component or system to the consumers. This paper is based on Ford's recent experience of researching and measuring to improve the end-of-line noise testing of its transmission manufacturing plant in Brazil. The approach is based on 6Sigma disciplines. There is not emphasis in the academic behaves of noise and vibration, or even the root cause of problems, but basically in the methodology in how to detect transmission noise still in the manufacturing line for immediate action and repair (if necessary) avoiding any issue to the consumer (internal - vehicle assemble line and vehicle buyers).

The extensive use of rotative machines in the diverse branches of the modern world has made the rising undesirable mechanical and acoustic vibration levels to be a problem of special importance for the machines normal operation as for the communities that are each time more affected by the problem. It makes the study of vibration and acoustic phenomena also to be even more important and the applications of its concepts more sophisticated. Several are the concepts used for decreasing vibration levels, like common dampers, hydraulic dampers, active dampers, natural frequencies changes and others. The choice of use of one or another depends greatly on the engineering possibilities (weight, energy, physical space, other components functional interference, vibration levels, etc.) as well as the cost of implementation of each one.

There are many different vibration sources in a car. Engine, gears, road roughness, impacts against the wheels cause vibration and sound that can decrease the parts and the car durability as well as affect drivability, safety and passengers and community comfort. In 4×4 cars, some extra vibration sources are the parts responsible for transmitting the torque and power to the rear wheels. Each of them has their own vibration modes, excited mostly by its imbalance or by the second order engine vibration. The engine vibration is a very well known phenomena and the rear driveshaft is designed not to have any vibration mode in the range of frequencies that the engine works or its second order. The imbalance of a driveshaft is also a design requirement. That means, the acceptable imbalance of the driveshaft is limited to a maximum value.

NVH (Noise, Vibration and Harshness) is an important vehicle attribute and focus in every Product Development at OEM'S (Original Equipment Manufacturers). Pass-by Noise is one of these aspects in order to improve noise vehicle as a whole. As a result, this paper will show opportunities that Pass-by Noise test can get in a new development of Commercial Vehicles, presenting the methodology, NVH improvements, Quiet Truck and Frequency Analysis as well as Robustness of Noise Package Development. Moreover, the presentation will consider all the requirements and the advantages that Pass-by Noise can accomplish in a new Sound Package Development to meet a new Conama Resolution. The focus on this topic is to meet a new Governmental Regulation (CONAMA 272/2000) and consequently improve overall noise quality showing procedures that will accomplish targets of NVH. Conclusions will present the advantages of the proposed method regarding to timing and cost and real cases examples will be mentioned.