Identification of Sound Source Model Using Inverse-Numerical Acoustic Analysis and Noise Prediction for Engine Enclosure

This paper describes the identification of a sound source model for diesel engines installed on agricultural machines by using Inverse-Numerical Acoustic (INA) analysis, and noise predictions using the sound source model identified by INA. INA is a method of identifying surface vibrations from surrounding sound pressures. This method can be applied to sound sources with complicated shapes like those in engines. Although many studies on INA have been conducted, these past studies have focused on improvements to the identified accuracy and prediction of noise in free sound field or hemi-free sound field. The authors accurately predicted the sound pressure levels of engine enclosures using a sound source model identified by INA and a boundary element method (BEM). However, we had not yet verified the effectiveness of this sound source model against enclosures that had sound absorbing materials and openings. We therefore constructed a sound source model of a diesel engine by using INA in this study. Moreover, we predicted the surrounding noise level of an engine enclosure that had sound absorbing materials and openings by using sound source model and BEM. The surrounding noise levels of the engine enclosure were measured and compared with the predicted results to verify the accuracy of prediction. As a result, we found the surrounding noise levels of the engine enclosure were accurately predicted using the sound source model. These results mean that a suitable design for the engine room to reduce noise is possible, by using the sound source model we obtained with INA.