A major problem in directly measuring synchronous belt noise is that, often, the noise coming from bearings, fans or any type of vibration transmitted through the belt drive may be taken for belt noise. In the automotive field, most of the times, the noise generated by belt drives is estimated using microphones in the proximity of belt, crankshafts, idlers...Such a method can be misleading, since it may easily include the contribution of background noise at some frequency. Moreover, a big amount of data is needed to test different layouts and running conditions. This work aims at developing a tool for estimating the acoustic radiation of synchronous belts during the design stage, one of the main objects being that of reducing the high number of tests currently employed. In a previous work it has been shown that 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 on the belt spans by a Scanning Laser Doppler Vibrometer, as input 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. This test bench has also been designed, realized and tested in order to keep at minimum the noise radiation due to other sources (electric motor, cooling fan, etc) and to be a proper reference for the model validation. Reference noise measurements have been performed by acoustic intensity techniques. The sound power values obtained from these measurements have been compared to those obtained by the Boundary Element model. In order to obtain a tool for the design stage, a dynamic model of the belt transmission, which is able calculate the amplitude of the transverse vibration of belt to be used as input for the Boundary Element model, is under development.
