Artigo:

During the internal combustion engine operation, the main noise sources are the crank train unbalance forces, the combustion phenomena, the gears coupling, the valves friction and intake and exhaust systems that radiate high noise due to air excitation of some parts resonant frequencies. A four cylinder engine intake manifold was analyzed in order to understand its contribution to the overall engine noise. An specific characteristic of this intake manifold is the presence of a resonator, which contributes to noise radiation from its surface, once the manifold is made of polymer that has lower stiffness when compared to aluminum. The proposal is to demonstrate the possibility of manifold radiated noise estimation by evaluating the panels velocities on its surfaces. Vibro-acoustic simulations were carried out using finite element method with automatically matched layer approach (AML). The sound pressure levels were determined using virtual microphones and panels velocities were calculated at some probes on the manifold surfaces. The results could be compared to NVH measurements in a semi-anechoic test cell. NVH tests and acoustic simulations demand considerable time and costs. Therefore, calculating and measuring only the panels velocities represent a good approach of the noise estimation.