A new approach to the measurements of transverse vibration and acoustic radiation of automotive belts using laser Doppler vibrometry and acoustic intensity techniques

This work aims at utilizing state-of-the-art and powerful measurement techniques to develop a tool for estimating the acoustic radiation of synchronous belts during the design stage. One of the main objects of this work is that of reducing the large number of tests currently employed. Effective measurement technologies, such as laser and acoustic intensity measurement techniques, are employed to support the entire development of the predicting tool, from the analysis of the noise and vibration phenomena to the validation of the numerical models. The proposed method can also be applied successfully to the analysis of noise generating mechanisms, especially belt vibration responses. In a previous work, it has been shown that the noise radiated at meshing frequency by a belt drive, simply composed of two pulleys and driven by an electric motor, can be estimated using vibration measurements, taken by a scanning laser Doppler vibrometer, as inputs for a boundary element model. The same approach is here extended to a more complex test bench, with an internal combustion engine cylinder head giving additional excitation. The test bench has been designed and realized in order to reduce the noise radiation due to interfering sources (electric motor, cooling system etc) and to make it possible to measure the noise contribution from the belt drive only. Reference noise measurements have been performed by acoustic intensity techniques. The sound power values obtained from these measurements have been compared to those obtained from the boundary element model. The techniques employed in this work have been shown to be able to analyse resonance and meshing phenomena on a real belt drive geometry, as had not been done before, based on the literature survey reported.