This paper is aimed at researching the interaction between aeroacoustic noise radiated from a rectangular cavity (gear bay) and from landing gear. It is a complicated flow-induced noise problem, involving the nonlinear, unsteady evolution of the turbulent structure inside the airflow bypassing the landing gear and the cavity. The generation and radiation mechanism of aeroacoustic noise are also concerned. In fact, it is a problem about the nonlinear interaction between the vortices shedding from the boundary layer of bluff bodies and the cavity-limited shear layer. To simplify this issue, a two-wheel landing gear named LAGOON is chosen as the landing gear model. The unsteady flow field and aerodynamic noise from it is simulated by applying the commercial software ANSYS Fluent. Good agreement is achieved between the numerical simulation and wind tunnel measurements in terms of the aerodynamic and aeroacoustic results. According to the size of LAGOON, a simple rectangular cavity is designed as the landing gear bay. Both the cavity combined with LAGOON and the cavity alone are simulated and compared. The results show that under the blocking effect of a strut, most small pieces of vortices at the trailing edge of the cavity bottom would dissipate rather than move forward along with the backflow, leading to the correlation of cavity resonance being more contrasting and increasing its amplitude. The blockage effect induced by rear wall could also enhance the turbulence kinetic energy at the wake of the strut, thus increasing the low-frequency noise radiated from the strut and cavity.