Study of Intake and Exhaust System Acoustic Performance Refinement with the Help of Vibro-Acoustic Analysis Tool 2010-01-1427

Increase in customer's awareness for better vehicle NVH has prompted automobile industry to address NVH issues more seriously. Among other critical vehicle systems for NVH, Air Intake and Exhaust Systems play an important role in terms of passenger compartment noise, sound quality and vehicle pass-by noise. Hence proper design & development of these systems is imperative to reduce their contribution in overall vehicle NVH. This needs to be achieved within constraints of meeting other functional requirements such as emissions and engine performance. The design parameters one needs to look at while developing the intake and exhaust system are mainly the acoustic transmission loss, structural noise radiations from the surfaces and structural isolation between body and these systems.

This paper demonstrates the use of FEM approach for Vibro-Acoustic Analysis as a practical means for design of intake and exhaust system in terms of high transmission loss. It also provides better understanding of the effect of various geometry parameters such as volume, porosity, internal construction, resonators, etc on the system transmission loss through out desired frequency range. Transmission loss is calculated for simple expansion chamber and Helmholtz resonator using analytical formula as well as standard Vibro-Acoustic Analysis. The predicted transmission loss using standard software are compared and validated against numerical calculations. Further Vibro-Acoustic methodology was used for transmission loss prediction of complicated real life systems such as Air Intake and Exhaust Systems. The methodology for modeling holes and sound paths in the exhaust muffler is discussed. The guideline for modeling resonators in terms of geometry and location is presented. The study of effect of different muffler parameters such as volume, internal construction, perforation diameter, and percentage perforation is also discussed. The parameters sensitive towards optimized noise and sound quality performance are highlighted. All the predictions and calculations for transmission loss are done assuming zero mean flow.