The interaction of turbulent flows with the external structure of ground vehicles generates uncomfortable noise and a lot of attention is devoted to find new mechanisms for its suppression. The present work is concerned with open cavity flows, very often found in the automotive industry. A three-dimensional rectangular very wide open cavity with aspect ratio L/D=4 at Reynolds number ReD=5000 and Mach number M=0.1 is considered. The passive control technique is based on eight different geometrical modifications: the length of the cavity, the radius of the trailing, leading and bottom edges and the difference in heights between the left and right wall of the cavity. Wall-resolved Large Eddy Simulations (LES) are used to obtain the flow fields and a post-process based on Curle’s analogy is applied to evaluate the acoustic radiation and the effectiveness of the control mechanisms. The results show that the modifications on the trailing edge are the most effective to control the flow. They allow to reduce the pressure fluctuations produced by the recirculation confined inside the cavity and the abrupt ejection of the flow at the trailing edge. As a consequence, the overall sound pressure level can be decreased up to 9 dB.