In this paper, the coupling computation of Computational Fluid Dynamics (CFD) and Computational AeroAcoustics (CAA) is conducted. Three operating conditions of the JT15D nacelle configuration are analyzed. Fan noise from the engine inlet is simulated in each condition. Computation is based on the Cartesian mesh method called Building-Cube Method (BCM). Firstly, the background flow is computed by a compressible Euler solver. And then, the noise propagation from the nacelle is computed by the Linearized Euler Equations (LEE) code. Finally, the far-field noise directivity is estimated by the Ffowcs-Williams and Hawkings (FW-H) method. The low speed flow around the JT15D nacelle was successfully simulated by using Simple Low-dissipative AUSM, which can deal with all speed flows. Sound wave propagation in the radial direction was pronounced at the lower frequency condition. In three conditions, the FW-H estimation of far-field Sound Pressure Level showed the good agreement with the experimental measurements qualitatively.