Control of interior Low Frequency Booming Based on Vehicle Liftgate Constraints

The liftgate is generally installed and fixed to the vehicle body through hinges, lock pins, sealing and buffers, whose rigid body modes vibrations are coupled with the passenger acoustic cavity modes, which are the main cause of low frequency booming noise. In this paper, a one-dimensional plate-cavity coupled analytical model including liftgate vibration and passenger acoustic cavity is established, and the effect of the boundary constraints stiffness on panel vibration and sound pressure level in cavity is analytically studied and experimentally verified in real vehicles. The theoretical results show that the sound pressure amplitude in cavity increases along the direction away from the liftgate and reaches the maximum value at the bottom location. The amplitude at the peak frequency of panel’s surface velocity and sound pressure level in cavity decreases with decreasing of stiffness of constraints. In the frequency range of 20−30 Hz, the amplitude at the peak frequency of sound pressure level at front seat is 8 dB(A) higher than that at middle seat and rear seat, which validates the theoretical results. The coupling sound pressure in the passenger cabin decreases with the increase of the relative position of the lockpin and the decrease of the relative height of the buffers. When the lockpin is increased 2 mm towards the rear of the vehicle body or the relative height of bumpers is decreased 2 mm, the liftgate vibration velocity can be reduced by 0.002−0.003 m/s, and the sound pressure level of the front row can be reduced by 3.5−14.8 dB(A).