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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

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.

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.

Acoustical materials are widely used in automotive vehicles and other industrial applications. Two important parameters namely Sound Transmission Loss (STL) and absorption coefficient are commonly used to evaluate the acoustical performance of these materials. Other parameters, such as insertion loss, noise reduction, and loss factors are also used to judge their performance depending on the application of these materials. A systematic comparative study of STL and absorption coefficient was conducted on various porous acoustical materials. Several dozen materials including needled cotton fiber (shoddy) and foam materials with or without barrier/scrim were investigated. The results of STL and absorption coefficient are presented and compared. As expected, it was found that most of materials are either good in STL or good in absorption. However, some combinations can achieve a balance of performance in both categories.

This paper presents the key issues regarding the measurement of damper (shock absorber) noises, including the type of microphones, the locations of microphones, the mini-anechoic chamber design considerations, selection of a shaker, and the observations gathered from conducting damper noise measurements in the Monroe Auto Equipment Company. The characteristics of two typical noises, a mechanical/click noise and a swish noise, generated by the dampers are discussed in detail. In addition, the functional features of a complete digital signal processing system, including A/D (analog-to-digital) and D/A (digital-to-analog) converters for the damper's noise and vibration measurements, are discussed in the paper.

The characteristics of automotive dampers (i.e. shock absorbers) noise are discussed in detail from both aspects of mechanical vibration and fluid flow induced noises. The measurements based upon industrial specifications of structure- and air-borne noises of automobile dampers are presented. Several noise reduction attempts were conducted on double-tube dampers at Monroe Auto Equipment Company. The results of these typical modifications and their physical implications are included in the paper.

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.

Research interest in vehicle NVH to improve riding comfort has increased significantly in the recent years. The air- and structure- born noise generated by the automotive shock absorber become a key factor to evaluate quality of vehicles. The ultimate goal of this study is to create a vibro-acoustic model of a shock absorber which can be used as a predictive tool by design engineers in the early stage of shock absorber design process. The efficiency of CAE tools developed in this study may also allow for more design iterations and alternatives within a relatively shorter design time, which may lead to a higher level of refinement and better-optimized design

This paper introduces an approach that uses a statistical energy analysis (SEA) method for prediction of noise in the vehicle cabin from an electric motor sound source placed in the engine compartment. The study integrates three different physics, namely, electromagnetics, harmonics, and acoustics. A 2004 Prius permanent magnet synchronous motor with an interior permanent magnet was used for performing the integrated CAE analysis, as the motor’s design details were readily available. The Maxwell forces on the stator teeth were first calculated by an electromagnetic software package. These forces were then mapped into a finite element model of the motor stator to predict the velocity profiles on the stator frame. Velocity profiles were considered as boundary conditions to calculate sound pressure levels and the equivalent radiated sound power level in the acoustic environment.