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The work carried out with external noise insulation has been demanding high importance in vehicle concept since the second External Noise Regulation in Brazil (Conama 001/ 1993). The engineering effort shall increase significantly for near future developments due to the new Regulation (Conama 272 / 2000) with more stringent limits. The effect over vehicle systems beyond noise requirements is not restricted to the addition of shields and insulators. The airflow restriction created by the noise shields surfaces may become a huge cooling issue. This situation is usually observed on trucks designed for tropical markets and submitted to severe environments. Lessons learned in a current development are the basis of the proposed methodology. Vehicle and lab sound intensity noise source ranking tests are suggested as development tools. The paper also presents a pass-by-noise development strategy that includes CAE airflow and cooling management tools.

A vehicle cooling system development and optimization success is strongly dependent on the prevention of recirculation zones and other areas of heat transfer and air flow concerns generated by underhood components. Traditionally, noise insulation package is defined without considering its impact on the thermal environment surrounding it. However, the airflow restriction created by the noise shields surfaces may become a huge air flow issue. This situation is usually verified on trucks designed for tropical markets and submitted to severe environments. This paper presents a development strategy coupling cooling and underhood air flow management package specification with pass-by-noise insulators design. The interaction between cooling and pass-by-noise developments must avoid the necessity of a later redesign phase. A CFD software, lab sound intensity noise source ranking tests as well as vehicle cooling testing are suggested as development tools.