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A reliable finite element model (FE model) for the suspension of front-engine front-wheel-drive vehicles (FF vehicle) was developed. The model allows analysis which clarifies the role of each suspension component for road noise reduction in the 130- 160 Hz range. To analyze road noise up to 200 Hz, an accurate suspension FE model including tire FE model was developed. All suspension components are modeled in detail by shell or solid element. This saves the validation of model and enables us to use it early in the design stage. To save calculation time, some suspension components in which structure is not a concern are transformed into modal model. To acknowledge each subsystem's role to the entire suspension system a new approach was introduced. In this approach, important internal forces between subsystems are selected. These internal forces have high contribution to transmissibility forces at the body attachment point (body transmissibility force).

A new method to predict low-frequency brake squeal occurrence was developed and guidelines for its elimination were formulated. First, a characteristic of the phenomenon was investigated using a simplified three-degree-of-freedom system model to obtain guidelines for squeal elimination, such as the natural frequency ratio of the brake rotor and caliper, an equivalent mass ratio of the brake rotor and caliper and the natural frequency and damping coefficient of the dynamic absorber. Then, a practical finite element model of the disk brake system was developed using Substructure Synthesis Method for design stage predictions. Finally, the usefulness of this method was confirmed by experimental validation.

Conventionally, sound insulation materials have been applied to control interior noise above 500 Hz, and damping materials to control interior noise below 500 Hz. In this paper, the noise control component for vehicle panels, which consists of damping material and sound insulation material, is investigated by using a two-degrees-of-freedom system. The investigation shows that sound insulation material can be effective in reducing interior noise below 500 Hz if its stiffness is reduced. This stiffness depends not only on the spring of the material itself but also on its pneumatic spring which is determined by air-flow resistance. This paper concludes with applications of techniques to reduce interior noise below 500 Hz by improving sound insulation materials.

An experimental simulation method has been developed for predicting the noise and vibration characteristics of a complete vehicle when body frame stiffness is changed. This method was developed by means of an improved transfer function synthesis method. Advantages over numerical simulation methods, such as finite element analysis include dramatic reductions in computation time. This experimental method is also very easy to carry out with a few measurement data. By applying this method to investigate the effects of stiffness changes of different vehicle components on low frequency road noise, effective ways of reducing road noise were proposed in the first stage of vehicle development.

A new experimental method, that enables to estimate the body and driveline sensitivity to unit transmitting error of a hypoid gear for automotive rear axle gear noise, has been developed. Measurements were made by exciting the tooth of the drive-pinion gear and that of the ring gear separately using the special devices designed with regard to simulation of acceleration and deceleration. The characteristic of this method is to estimate the forces at the contact point of the gears. Estimation of these forces is carried out under the condition that the higher stiffness is provided by the tooth of the drive-pinion gear and that of the ring gear, compared with the stiffness of the driveshafts and that of the propeller shaft etc., and relative angular displacement of the torsional vibration between the teeth of the drive-pinion gear and those of the ring gear is constant.

An experimental method for the reduction of the steering wheel vibration, occurring at high speed cruising and/or at engine idling, is described. The reduction of the vibration can be achieved by increasing the resonant frequency of the steering system, which is constructed of a steering wheel, steering column, its support member and so on. Mechanical impedance methods were applied to predict the resonant frequency by means of converting the diametrical moment of inertia of the steering wheel into an equivalent mass. This method provides an insight into how design should be changed to obtain further reduction of the steering wheel vibration. Practical applications are also discussed.

In order to reduce the interior noise of a vehicle with a four-cylinder engine, investigations were made using finite element and vector methods, acoustic intensity testing and holography technique. The investigation resulted in inclination of the engine mounting, design changes to the front suspension member, a shock absorber engine mounting, structural modifications to reduce body panel vibration and a new engine mounting to insulate high frequency engine vibration.