## 1 Introduction
An integrated experimental and analytical modeling approach aimed at examining the impact noise characteristics of automotive-type timing chain drive systems was presented in [6], where a comparative study between various system parameters and operating conditions was provided. An acoustic model relating the dynamic response of rollers and corresponding induced sound pressure levels is developed in [7], where the acceleration response of each chain roller for the noise level prediction of a chain drive under varying operating conditions was studied by a FEM (finite element method) approach. Timing chain systems were modeled in [8] by a theoretical approach considering mass viscoelastic contact characteristics of each link or tooth separately. A new roller chain sprocket tooth geometry for engine camshaft drives was studied in [9], having as a target the reduction of noise levels during meshing. Experimental tests were carried out to compare the noise levels of the asymmetrical sprocket tooth profile to that of a standard ISO sprocket tooth profile. Experimental studies of timing chain vibration aimed at avoiding acoustically critical excitations were carried out in [10]. The modeling of the entire timing drive system containing a bushing chain drive, camshafts, and all connected single valve train was presented in [11], where the primary dynamics of the chain drive and the forces which are transferred to the engine's structure were assessed. The torsional oscillations of engine camshafts induced by valve train loads were studied in [12]: they can cause significant tension fluctuation in the timing chain with corresponding increase in the chain transverse vibrations; this in turn causes an undesirable impact noise from the chain or sprocket meshing process. In this work, the use of acoustic boundary elements and structural finite elements is aimed at the prediction of the radiation of structural noise from a side cover. A comparison is made between numerical results and experimental measurements, and a discussion is provided for the practical application of these modeling methods to side cover design. As a matter of fact, a computational method to allow reproducing the actual performance of a component for a car engine from a vibro-acoustic point of view was developed. The vibro-acoustic numerical and experimental analysis was carried out for the chain cover of a low-powered four-cylinder four-stroke diesel engine (Figure 1a), belonging to the FPT (Fiat Power Train) family called SDE (Small Diesel Engine). By applying a methodology used in the acoustic optimization of new FPT engine components, firstly an FEM approach was applied for a modal analysis of the overall engine and also for a forced response analysis of the only chain cover. For the latter, the applied boundary conditions were the accelerations experimentally measured by accelerometers located at the points of connection among chain cover, head cover, and crankcase. Subsequently, a boundary element model of the only chain cover was realized to determine the chain cover noise emission, starting from the previously calculated vibrations [13]. The numerical vibro-acoustic outcomes were compared with those experimentally observed. All the information thus obtained allowed the identification of those critical areas--in terms of noise generation--on which to undertake necessary improvements. The modelling and computation were carried out with the support of the Hypermesh [14] and Abaqus [15] codes for the FEM modelling and modal analysis, and SIEMENS-LMS/Virtual Lab [16] for the BEM (boundary element method) modelling and vibro-acoustic analysis. In particular, Hypermesh code was used for the FEM mesh generation. The aforementioned software suites were selected being those in use in FPT at the time the work was performed.