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Sunroof buffeting noise is annoying to drivers and passengers. The conventional method for suppressing sunroof buffeting noise is to use passive deflectors. A recent trend has been large sunroof openings, such as panoramic sunroofs, in accordance with customer preferences for a feeling of openness. Since sunroof buffeting noise tends to become louder as the sunroof opening area becomes larger, a conventional passive deflector may not be a solution in this case, and a new effective method for reducing the sunroof buffeting noise is required. Previous work showed that a strong, self-sustained tonal noise, generated from a Helmholtz resonator exposed to a grazing flow, could be significantly reduced by closedloop control of an active deflector installed near the upstream edge of the resonator opening. The active deflector system is a cascade of a microphone sensor mounted inside the cavity, controller, power amplifier, and deflector mechanism vibrated by a voice coil actuator. Since the acoustic pressure inside the cavity is influenced by the shear layer modified by the active deflector, the active deflector and acoustic response of the cavity form a closed-loop control system. The main objective of the present study is to implement this technology on a real vehicle and evaluate whether the technology can be utilized to suppress sunroof buffeting noise. A simple active deflector system was assembled and installed in a compact-sized hatchback car with a sunroof opening length of 460 mm. The active deflector system was tested both in a wind tunnel and on a proving ground. The test results showed that the active deflector reduced the sunroof buffeting noise by as much as 25 dB. The active deflector was shown to be stable and robust regardless of changes in the wind speed and wind yaw angle.

This research aims to develop a method to efficiently reduce the body input force from the chassis due to road-induced excitation. To this end, the frequency response function–based substructuring method is employed to model the vehicle cross member and coupling points. Using this model, the dynamic stiffness modification factor of elastic bushing at the effective path is predicted for reducing road noise. Because of the difficulties in directly obtaining dynamic properties of body mount bushings pressured into the sub-frame, the frequency response function–based substructuring model and inverse formulation method are used to indirectly estimate the bushing’s dynamic properties. Therefore, the primary focus of this study is to validate the feasibility of using the inverse formulation method for deriving road noise improvement factor on a simple cross member application. In this feasibility validation, road excitation is simply substituted with a shaker excitation in vertical direction. The previously developed suspension rig that enables a direct measurement of the body input force at the coupling points and the specially developed cross member jig are used for the validation test.

This study aims to estimate the change in suspension to body input force transmission due to the softening of the connecting elastomer under rolling excitation. In this respect, the suspension coupled to a vehicle body via an elastomer bushing is modeled using point impedance. A numerical study is performed for achievable force reduction due to a softened bush under the influence of different impedance combinations for the suspension and the vehicle body. Following a numerical study, the proposed model is validated through empirical testing of McPherson strut type suspension in the lateral arm Y direction and multilink type rear suspension in the front mount X direction, which represent extremely stiff and extremely soft coupling cases for the suspension type, respectively. Due to the difficulties in measuring road-induced operational forces within an actual vehicle, a validation test is performed using a previously developed rig that enables direct measurement of the force without modifying the structure of the suspension. Additionally, the rig-measured force, which is potentially misleading due to the large deviation in stiffness between the rig and an actual vehicle, is investigated under varying combinations of suspension and bush stiffness.

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