Two-stage combustion was generated by two-stage fuel-injection with a single cylinder diesel engine. The sound source locations were identified for one of the main noise frequencies by using a sound source visualization device for different second fuel-injection timings, -10 deg. ATDC and -6 deg. ATDC, when the two-combustion impacts are amplified and cancelled at 2500 Hz, respectively. The results show that there were a few sound sources and the sound pressure level near each sound source increased first, attained maximum and decreased over time. The maximum sound pressure level for each sound source for the second stage fuel-injection start timing of -10 deg. ATDC was greater than that for the second stage fuel-injection start timing of -6 deg. ATDC. The decay rate was greatest for the sound source with the maximum sound pressure level in the present engine.