The space distribution and frequency spectrum of the sound pressure and acoustic intensity emitted from the outer surface of an internal combustion engine are analyzed by both the boundary element method and the usual simple method. The experimental value of the vibrational velocity of the outer surface of the cylinder block when a piston head is excited, is used as the input data of the above calculation. The sound pressure and acoustic intensity around the actual engine are measured by the vibration test when a piston head is excited with harmonic force under conditions of a non-reflective room. Accuracy of the calculated results, both by the boundary element method and by the usual simple method, are investigated by comparing them with the experimental results.
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