Search Results

In this paper, an analytic method has been developed to effectively evaluate the acoustic performance of a vehicle when a traditional sound package component is replaced by a lightweight sound package component. This method avoids the expensive full vehicle tests and statistical energy analysis (SEA) model simulations, and can be used to evaluate the results quickly with acceptable level of accuracy. The developed method is verified by comparing the results with those obtained from a chassis dynamometer test and a full vehicle SEA model simulation. Good correlation is observed between the test and the model. Some parametric studies regarding the performance of lightweight sound packages are also carried out using the method developed in this paper.

This paper discusses the approach and application of controlling material and manufacturing parameters in development of lightweight acoustic interior systems. First addressed is the theoretical premise of noise control mechanisms and their relationship to material property/process sensitivity through poroelastic model simulation. The optimal balance of sound transmission loss and absorption in achieving optimally tuned acoustic performance is then presented along with material sample and in-vehicle experimental results. The ability to acoustically tune the vehicle interior to a desired sound level and frequency content through proper design & control of the elastic porous properties achieved by unique acoustic material/process flexibility & capability is demonstrated.

The Collins & Aikman Technical Centre in Plymouth Michigan contains over 1800 square meters of laboratory space dedicated to the design and development of cost effective solutions to vehicle noise and vibration problems. The facility houses North America's first indoor test facility capable of undertaking vehicle passby noise testing in accordance with both federal and international standards. It also houses a transmission loss testing suite capable of accommodating a full size van, a Quiet Room with under vehicle pit access for engine noise simulator testing and modal analysis, a conference room for sound quality/jury testing, a workshop, a prototyping area and a vehicle wash. This fast track design build project offered many acoustical challenges requiring innovative solutions to meet both schedule and budget.

Recent stringent government regulations on emission control and fuel economy drive the vehicles and their associated components and systems to the direction of lighter weight. However, the achieved lightweight must not be obtained by sacrificing other important performance requirements such as manufacturability, strength, durability, reliability, safety, noise, vibration and harshness (NVH). Additionally, cost is always a dominating factor in the lightweight design of automotive products. Therefore, a successful lightweight design can only be accomplished by better understanding the performance requirements, the potentials and limitations of the designed products, and by balancing many conflicting design parameters. The combined knowledge-based design optimization procedures and, inevitably, some trial-and-error design iterations are the practical approaches that should be adopted in the lightweight design for the automotive applications.

This paper is to present a systematic study on many critical factors, such as angle of the testing panel, total scanning time of the intensity probe, source room noise level, number of microphones used in the source room, sample size, distance of the microphone in the source room, intensity probe spacer size, measurement time, and receiver room size. Additionally, three noise factors; background noise level, operator and measurement distance were also included. It were discovered that test panel angles and sample sizes were the two most dominant factors. All of above are relevant to experimental SEA or SEA validation process. The complete test results and the experience gained are presented in the paper.

Brake squeal is an instability issue with many parameters. This study attempts to assess the effect of thermal load on brake squeal behavior through finite element computation. The research can be divided into two parts. The first step is to analyze the thermal conditions of a brake assembly based on ANSYS Fluent. Modeling of transient temperature and thermal-structural analysis are then used in coupled thermal-mechanical analysis using complex eigenvalue methods in ANSYS Mechanical to determine the deformation and the stress established in both the disk and the pad. Thus, the influence of thermal load may be observed when using finite element methods for prediction of brake squeal propensity. A detailed finite element model of a commercial brake disc was developed and verified by experimental modal analysis and structure free-free modal analysis.

A systematic benchmarking study was performed to investigate the acoustic performance of production floor coverings (i.e. carpets) of vehicles. A larger number of passenger cars including compact, mid-size, full size, and a truck were selected. The floor coverings were removed from these vehicles and evaluated both on absorption and sound transmission loss (STL) performances. The methodology used and the experimental results are presented in this paper. It was discovered that the design of the carpet is more important than the materials used. In addition, a carpet with highest absorption does not necessarily have the best STL and vice versa. However, an optimum design could achieve high performance in both categories.

Determination of the sound transmission loss (STL) of a vehicle component that has a large aperture, such as an air exhauster or an air extraction opening, always presents a challenge to an acoustics engineer. The complexity of the aperture's physical conditions cannot be easily solved with conventional, analytical or numerical methods. A systematic study of investigating the transmission loss characteristics of the large aperture is presented in this paper. Both conventional potential noise reduction predictions of large apertures and SEA simulations were performed. Transmission losses with different acoustic treatments were measured and predicted when using AutoSEA2. Finally, correlation between measured results and predications were developed. The ultimate goal of this study is to reduce the costly transmission loss measurements with correlated analytical estimations

This paper presents a systematic measurement approach for localizing the acoustic leakage of pass-through components and for determining the pass-through effects on sound transmission loss through the front vehicle dash section. The dash section is cut from a current vehicle platform and is installed on the wall of a sound transmission loss suite in which the source side is a reverberant room and the receiver side is a quiet room. The proposed approach is based on the widely-used sound intensity technique. The transmitted point and spatially averaged sound intensities through the dash section are measured with the careful control of noise flank paths and reactive fields. The approach includes sequential steps of measurements on the dash section: (1) bare panel with all holes sealed; (2) with dash insulator installed; (3) with each of four pass-through component groups installed; (4) with all pass-through component groups installed; (5) with instrumental panel installed.