Search Results

SEA models are used to predict the performance of acoustic packages when assessing the performance of vehicle level or body noise reduction targets. One of the challenges faced by CAE engineers is the ability to estimate the performance of different materials used in the sound package at the design stage. Analysts can use measured data in the form of insertion loss and random incidence absorption if available or can predict the performance of materials using a Biot type description. The use of the full poro-elastic Biot model for materials requires knowledge of the fluid and elastic properties, however a limp or rigid model can be used to describe the material based only on the fluid properties and this is often sufficient to describe fibrous materials. In this paper a method will be outlined which will allow the material properties of fibrous materials to be estimated from basic normal incidence data that is provided by material suppliers.

The excitation of structural modes of vehicle roofs due to structure-borne excitations from the road and powertrain can generate boom and noise issues inside the passenger cabin. The use of elastomeric foams between the roof bows and roof panel can provide significant damping to the roof and reduce the vibration. If computer-aided engineering (CAE) can be used to predict the effect of elastomeric foams accurately on vibration and noise, then it would be possible to optimize the properties and placement of foam materials on the roof to attenuate vibration. The properties of the different foam materials were characterized in laboratory tests and then applied to a flat test panel and a vehicle body-in-white. This paper presents the results of an investigation into the testing and CAE analysis of the vibration and radiated sound power of flat steel panels and the roof from the BIW of an SUV with anti-flutter foam and Terophon® high damping foam (HDF) materials.

A reactive aftermarket automotive style muffler was considered for development and validation of a procedure to numerically predict and experimentally validate acoustic performance. A CAD model of the silencer was created and meshed. The silencer interior included two sections of perforated pipe, which were included in the cavity mesh. A hybrid FE-SEA (Statistical Energy Analysis) numerical model consisting of a finite element acoustic cavity excited by a diffuse acoustic field at the inlet and coupled via hybrid junctions to SEA semi-infinite fluids on both the inlet and outlet. The hybrid FE-SEA model solves very rapidly on a desktop PC making iterative numerical design a realistic option. To validate the predictions, an experimental setup was created to directly measure the muffler insertion loss. This was done by using a broadband acoustic source piped into a hemi-anechoic chamber.