Acoustic Modal Analysis and Transmission Properties of a Prototype Induction System

The objective of this study was to determine whether standard modeling packages could be used to predict the acoustical response of an IC-engine induction system. To determine the answer to this question, we constructed from acrylic plastic a “prototype” induction system for a four-cylinder engine. Two modeling packages were used. The first package used was BEMAP, a boundary element program designed specifically for acoustical modeling. The second package used was ANSYS, a general purpose finite element program. For both BEMAP and ANSYS, a radiation boundary condition was used at the air intake of the induction system. Results from BEMAP and ANSYS are compared to experimental data. The experimental results were obtained by exciting one of the induction system intake ports with a small loudspeaker and measuring the transfer function between the sound pressure at the air inlet and the sound pressure at the intake port. All three sets of results exhibit good agreement.