Abstract: The liquid-solid coupling model of a constrained-layer damping oil pan as well as the infinite model of the radiation acoustic field were established. The vibration accelerations of bolts， which were loaded in bolt holes for calculating the radiation acoustic field， were measured. The simulated value of sound pressure was acquired at the point which is vertically 10cm from the bottom center of the oil pan， and the value is extremely consistent with the measured value in the range of 500 to 3000Hz， proving preciseness of the acoustic calculation. Total value of A-weighted sound pressure level of radiation noise and the loudness value were respectively regarded as the objectives to optimize the oil pan. The results indicated that the noise with less sound pressure may make the noise sound louder， and only if the sound quality parameters are considered as optimization objectives， the NVH performance can be consequently improved effectively. Finally， the adaptive simulated annealing algorithm was adopted to optimize the thickness of the layers of the constrained-layer damping oil pan， with the loudness of radiation noise as the optimization objective. The result shows that the loudness value declined by 27.3%， reduced 40.0 sone and the mass can be reduced by 21.2%， and the NVH performance is promoted obviously.

Key words: constrained-layer damping, liquid-solid coupling, infinite element method, adaptive simulated annealing algorithm, loudness