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Pass-By-Noise (PBN) requirements area an important aspect of NVH development of a commercial vehicle. The PBN on an Intermediate commercial vehicle (ICV) with refrigerator container was the subject of this study. This vehicle emitted PBN greater than accepted threshold due to its configuration. The overall approach to identify the sources and contributors for PBN was to test the vehicle in its baseline condition as well as with improvements. Near source noise measurements were performed at all potential noise contributors. A windowing technique was used to identify the potential noise sources. This Windowing technique is the exposing of each individual noise source while keeping all others shielded. This technique is reliable and quickly reveals significant noise contributors. Improvements to noise sources were reviewed for effectiveness to the overall PBN and overall recommendations were made.

In commercial vehicles, exhaust system is normally mounted on frame side members (FSM) using hanger brackets. These exhaust system hanger brackets are tested either as part of full vehicle durability testing or as a subsystem in a rig testing. During initial phases of product development cycle, the hanger brackets are validated for their durability in rig level testing using time domain signals acquired from mule vehicle. These signals are then used in uni-axial, bi-axial or tri-axial rig facilities based on their severity and the availability of test rigs. This paper depicts the simulation method employed to replicate the bi-directional rig testing through modal transient analysis. Finite Element Method (FEM) is applied for numerical analysis of exhaust system assembly using MSC/Nastran software with the inclusion of rubber isolator modeling, meshing guidelines etc. Finite Element Analysis (FEA) results are in good agreement with rig level test results.