This paper presents the numerical studies on the effect of atmospheric turbulence on sonic boom signatures. The authors developed the SPnoise for Sonic Boom, which is a numerical analysis code to simulate the essential effect of atmospheric turbulence on sonic booms, i.e., fluctuation of the medium due to turbulence and focusing/defocusing of a sharp wavefront as a result of diffraction. Waveforms obtained from SPnoise for Sonic Boom are compared with those by sonic boom measurements from D-SEND#2, the second flight test of the Drop Test for Simplified Evaluation of Non-symmetrically Distributed Sonic Boom project, and fairly good agreement between simulated and measured waveforms is achieved.