Active Contol of vibrations & Noise and applications of AI/ML fo automotive NVH

A: The correct choice maintains stiffness and corrosion resistance so the sensor phase stays stable over life. B fails when e‑coat chips and crevice corrosion shifts preload. C creeps under clamp load and walks the resonance. D corrodes aggressively in chloride splash and drifts fastest despite conversion coating.

A: The correct answer identifies a risk the muffler was never sized to address. A is still attenuated partially by passive volume. B is perceptible but energy‑limited. D remains filtered by the same acoustic path the muffler already handles.

A: The symbol enforces a consistent signal sign so the controller converges. B is set by capsule design, not the drawing. C is handled in the schematic, not GA. D would be called out with datums and angles, not a phase note.

A: The correct value comes from c/2L giving a low‑hundreds‑of‑Hz ceiling for small cars. B drops a zero and confuses structural modes. C uses c/L not c/2L. D doubles the frequency without a physical basis from trim mass.