Research on Abnormal Noise in an Inline Six-Cylinder Engine Based on Sound Source Localization and Modal Analysis

This study addresses the abnormal noise issue in an inline six-cylinder engine during acceleration through noise testing and near-field microphone array-based sound source localization, combined with engine modal coupling theory and analytical methods. The results of testing and modal analysis indicate that the overlap of modal parameters between the engine crankshaft system and cylinder block leads to structural resonance under high-speed operation, which is identified as the root cause of the abnormal noise. The diagnostic conclusion was further validated through experimental verification. To mitigate the resonance, a high-stiffness spacer block was added between the vibration damper and crankshaft to adjust the overall modal parameters of the crankshaft system. This optimization effectively avoided resonance, reducing the near-field noise at the engine front end by 3.9 dB(A). The findings provide valuable insights for abnormal noise diagnosis and optimization strategies in engine systems.