Search Results

This paper describes the work carried out to assess the structure-borne and airborne contributions in the Rieter APAMAT II testing machine. The APAMAT II system was designed to measure the effectiveness of various trim and barrier treatments in automotive interior applications. The individual structure-borne and airborne contributions from the ball impact on the treated panel cannot be obtained directly from the sound pressure level measurements in the receiver chamber of the system. A hybrid modeling technique is proposed that incorporates finite element (FE) and statistical energy analysis (SEA) methods to develop vibro-acoustic models across the entire frequency range for analyzing transmission characteristics of various trim configurations. This provides an analytical model that can adequately predict the vibro-acoustic response under structure-borne loads at low to mid frequencies.

Sound transmission loss and sound absorption measurements are conducted to characterize acoustical performance of noise control materials and components used in vehicles. These measured data are often used to select materials and define acoustical targets. It is imperative to have accurate and repeatable data. Process variability is often monitored using measurement data collected over time. A certain amount of variability due to random causes is always expected. Acoustical measurements have inherent variability from different operators, equipment, test setup, environment etc. When variation in the measurements is due to random causes the measurements are in-control and measured data are considered “good”. However, special cause variations in the measured data such as operator error or setup error must be identified and corrected. Control chart is a popular statistical tool for monitoring process variability and improving quality.

OEMs are racing to develop lightweight vehicles as government regulations now mandate automakers to nearly double the average fuel economy of new cars and trucks by 2025. Lightweight materials such as aluminum, magnesium and carbon fiber composites are being used as structural members in vehicle body and suspension components. The reduction in weight in structural panels increases noise transmission into the passenger compartment. This poses a great challenge in vehicle sound package development since simply increasing weight in sound package components to reduce interior noise is no longer an option [1]. This paper discusses weight saving approaches to reduce noise level at the sources, noise transmission paths, and transmitted noise into the passenger compartment. Lightweight sound package materials are introduced to treat and reduce airborne noise transmission into multi-material lightweight body structure.

SAE acoustics materials committee published updates of SAE J1400 Standard - Laboratory Measurement of the Airborne Sound Barrier Performance of Flat Materials and Assemblies in 2017. In the standard, a control sample is defined with a specific construction to determine the suitability of the test suite. A set of measured sound transmission loss data of the control sample are included in the published updated standard. Autoneum North America Acoustics Laboratory constructed a control sample based on the design in the standard. Sound transmission loss (STL) measurement of this control sample was performed and results are consistent with published data below 2000 Hz. Above 2000 Hz, STL results are above published limits. Sound intensity measurement and flanking noise paths measurements confirmed the measured STL values of the control sample.