How is modal analysis used in NVH development?

Modal analysis identifies natural frequencies, mode shapes, and damping of structures. In NVH development, it reveals resonances that amplify vibration and noise. Methods include impact hammer testing (quick assessment using roving impact or response), shaker testing (higher force for accurate damping), and operational modal analysis (measuring in running condition). Results inform CAE model correlation, identify problematic modes requiring tuning, and guide structural modifications. Targets include separating body modes from engine excitation frequencies and ensuring adequate modal density for good acoustic behavior.