Title: Interior Noise Reduction in a Passenger Vehicle through Mode Modulation of Backdoor
text: Inside cabin of a passenger car, low frequency booming noise still presents a major hurdle for NVH engineers to fine tune a vehicle. Low frequency booming noise is presently taken care with addition of mass damper and large reinforcements. These conventional countermeasures add weight to the vehicle as well as increase the overall production cost. The study presented in this paper proposes a countermeasure model that not only reduces the booming noise but also avoids any weight and cost addition. It has been focused for low frequency booming noise around 30 ∼ 40 Hz. Within the range mentioned, one of the major reasons for booming noise in hatchback models is the bending resonance of backdoor. By modifying the mode of the backdoor in such a manner that it cancels the effect of bending on the vehicle acoustic cavity, improvement can be achieved in terms of sound pressure level at the driver’s right ear location (DREL). Present study utilizes an innovative approach to change the bending mode of the backdoor into twist mode. This has been achieved by offsetting the latch and striker assembly from conventional center location to either side on the transverse axis. The study has been done on a correlated full vehicle trimmed model of a subject vehicle. Maximum improvement of 6 dB(A) has been achieved through the proposed countermeasure. The countermeasure has been applied horizontally to all hatchback models having a backdoor that opens downside-up. The effect of the countermeasure was found to be substantial.