Sound Power Emission on an Efficient Diesel Engine using 3D Acoustic Imaging Techniques

The identification and characterization of sound power radiated by engine components is an important challenge for car manufacturers such as PSA. This paper will show the approach used, the results obtained and the analysis of those results during a study done with PSA to evaluate the contribution of each component on the total sound power radiated by an engine.
In the first part of the study, a standard 2D acoustic imaging technique, based on combined holography and beamforming method, was used to evaluate the sound power radiated by faces of an engine and to identify the most radiating areas. In the second part of this study, an innovating technique has been applied, using a 3D meshing of the engine an precise definition of each component on this
meshing. Based on measurement done on an acoustic array successively positioned on four sides of the engine and a precise positioning of the array in regards to the meshing, it is possible to rebuild the sound power radiated by elements of the meshing and thus obtain the sound power spectrum radiated by each components of the engine for various configurations.

Such experimental data have many interests for PSA:
• At first, it gives data concerning the overall acoustic power level of this engine.
• It gives information about the noisiest sources on each face of the engine. So, it gives orientation concerning the strategy of the noise reduction of the engine.
• It provides data to fix the different acoustic targets. By having the sound power level and spectrum of the mainly components, it is possible to build the targets to achieve by the suppliers on their benches. The comparison between the overall sound power level and the “sum-up” of the sound power level radiated by each component is a good way to be confident about the coherence between the overall target and the declined targets.