How would you diagnose and resolve a low-frequency boom noise occurring during steady-state highway cruising?

Low-frequency boom diagnosis involves: First, identify the excitation frequency through order analysis to determine if source is engine firing order, driveline, or tire cavity resonance. Use transfer path analysis to identify primary transmission paths. For powertrain-excited boom: Check powertrain mount tuning against body acoustic mode frequencies, evaluate structural sensitivity at attachment points, assess acoustic cavity modes using acoustic FRF. Countermeasures include: Mount retuning to shift frequency coupling, body stiffening to move structural modes, acoustic treatments (damping, barriers), and active noise cancellation for persistent tonal content. Resolution requires balancing isolation versus driveability and addressing both source strength and transfer path efficiency.