The recently updated pass-by noise measurement procedure prescribes a mix of acceleration tests and constant speed tests. This has led to an increased relevance of tire noise relative to the past, when the procedure prescribed only acceleration tests. In addition, the next phase of the roadmap for pass-by noise limits for passenger vehicles is 70 dB(A) by 2020, later followed by 68 dB(A). In this context, exterior tire noise has drawn increasing attention. OEMs, suppliers of passive acoustic treatments, road manufacturers and tire manufacturers are, at the moment, devoting strong efforts to the definition of solutions for the control of exterior noise.
This paper is concerned with the potential of existing passive exterior treatments to reduce the exterior noise generated by the tires. Different countermeasures are analyzed, namely wheelhouse liners, under-engine shields, under-body panels and under-trunk panels. The goal is to provide a sensitivity analysis with respect to the absorption characteristics and a ranking of the relevance of these treatments in the perspective of taking rational decisions to lessen the exterior noise. Results are based, on one hand, on advanced FEM simulation applied on a full generic vehicle and, on the other hand, on ATF measurements done on a European C-segment vehicle. In this way, in one single predictive system, all the acoustic parts likely to contribute to the reduction of tire noise are taken into account. Plus, it is possible to derive part configuration solutions associated with quantified objective of pass-by noise reduction.