How is modal analysis used to optimize vehicle NVH performance?

Modal analysis identifies natural frequencies and mode shapes of the body structure. Key targets include: Avoiding resonance between body modes (typically 25-40 Hz for first bending/torsion) and engine firing frequencies, Separating steering column mode from idle shake frequencies, Ensuring panel modes don't couple with acoustic cavity modes. Optimization involves adjusting stiffness (gauge, material, joints), mass distribution, and damping. FEA modal analysis guides design, validated by experimental modal analysis (EMA) using impact hammers or shakers with accelerometers. MAC (Modal Assurance Criterion) correlates FEA to test.