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The process for setting the marketability targets and achievement methods for automotive interior quietness (as related to air borne noise above 400Hz, considered the high frequency range) was established. With conventional methods it is difficult to disseminate the relationship between the performance of individual parts and the overall vehicle performance. Without new methods, it is difficult to propose detailed specifications for the optimal sound proof packages. In order to make it possible to resolve the individual components performance targets, the interior cavity was divided into a number of sections and the acoustic performance of each section is evaluated separately. This is accomplished by evaluating the acoustical energy level of each separate interior panel with the unit power of the exterior speaker excitation. The applicability of the method was verified by evaluating result against predicted value, using the new method, during actual vehicle operation.

This paper describes the porous materials FE modeling scheme inside vehicle cabin using measured acoustic impedances to reduce the size of the matrices of the FE model while keeping the accuracy. The technique of measuring acoustic impedance using PU probe in a free field is introduced. Next, the surface acoustic impedance of the seat by the side of front is measured using this technique. And the vehicle cabin acoustic field is modeled by FEM using the measured surface acoustic impedance. For the accuracy verification of this model, the acoustic transfer characteristics inside vehicle cabin with and without the front seat are compared with the predicted and the measured transfer function. Moreover, finally the worth of this modeling method is considered.

To solve interior rolling noise issues after vehicle development has been finalized, a robust procedure is desired, which combines the strengths of both the experimental and the simulation world. This paper proposes a methodology that is focused on rolling noise issues in the frequency range from 100 to 600Hz and whose core is constituted by a source identification procedure. By means of an inverse method that makes use of the information coming from several microphones, each of the interior areas of the passenger compartment walls is identified as an equivalent source and one can then determine which one is the most contributing to the interior noise under operating condition. This allows a direct and optimized application of countermeasures aimed at the reduction of the interior rolling noise.

This paper describes an effective method with statistical energy analysis (SEA) for specifying the vehicle sound proof package that achieves the best balance between light weight and high sound insulation performance. For proposing the sound proof package in the early stages of vehicle development, it is necessary to assess a number of specifications and to pick the best design specifications for weight and sound proof performance. However, there are difficulties in achieving conflicting objectives simultaneously, and acoustic engineers need special technical know-how. In this study, a new automated optimization method is proposed that approaches the problem above. As a result, detailed sound insulation package specifications, including the thickness distribution of each part, can be obtained and these can be easily transferred to drawings. Moreover, the accuracy of this method is proven by a reduction in vehicle interior cabin sound pressure level

This paper describes an effective method of developing a soundproof package, which balances both light weight and high noise insulation performance. Since it is required to propose design of sound insulator in the early stages of the development, the hybrid statistical energy analysis (SEA) modeling method is applied, which is practical for high frequency analysis. Also an acoustic characteristic estimation technique of the multi layer structures is used. As a result of applying these effective methods, the 2006 brand-new vehicle categorized as C has enhanced in road noise quietness and decreased in weight as compared with the previous model.

A hybrid SEA modeling scheme has been developed and applied to obtain an accurate SEA model for a passenger car. In this study, using the SEA model as a reference, uniqueness of the SEA model will be discussed. The SEA model uniqueness will be measured in terms of how accurately dominant power flows are described in comparison with the reference SEA model. An innovative scheme to quantify the differences of the dominant power flow between the test SEA model and the reference SEA model will be developed. Using the scheme, it will be shown that the test SEA model approaches to the reference SEA model as the energy ratios are being matched. Here, the energy ratios, between input power subsystem and a subsystem responding to an excitation given to the input power subsystem, are measured. They have been used to develop the reference SEA model.

A hybrid SEA modeling scheme has been developed and applied to obtain an accurate SEA model for a passenger car. In this study, the detailed workflow associated with the hybrid SEA modeling scheme will be described. Each step in the workflow will be discussed in terms of the obtained data, the corresponding analysis and results. In those steps, several innovative methods for developing the hybrid SEA model will be presented. Finally, a road noise analysis will be performed using the hybrid SEA model to validate the SEA model for the passenger car. In order to demonstrate the accuracy of the model, the analysis results such as the sound pressure level of car interior will be compared with the measurements.