Pass by Noise Reduction on a Commercial Vehicle

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. By implementing these recommendations, the required noise reduction was achieved and the vehicle met the PBN target. These results have validated this approach for the identification of noise contributors and effectiveness of counter measures.