From an ecological point of view, detection and localization of an approaching object as accurately as possible is an essential ability. There are two causes of approaching sound sources - a listener's movement towards a stationary sound source (LM) and a sound source's movement towards a stationary listener (SM). While both cases provide identical acoustic signals, self motion information is only available in the LM case. The aim of the present study was to compare these two conditions (LM and SM), focusing on the perceived amplitude variations in estimating distance travelled to an approaching sound source. The experimental setup consisted of a parallel swing configured for back and forth motion the sagittal plane (0.33 Hz, 20 cm max displacement), one active loudspeaker (38 cm from the listener), and one dummy loudspeaker (95 cm from the listener). The sound signal stimulus was a 1.5 s pink noise burst. The sound pressure level (SPL) of the active loudspeaker was modulated by the swing's motion to simulate the sound from the dummy loudspeaker. Participants sitting on the chair placed in the experimental position looked at the experimental setup before were blindfolded. Participants’ task was to compare the perceived change of the sound pressure level caused by the motion of the participant and/or the sound source with the change imaged by participants that it should be for the experimental setup. The point of subjective equality between perceived and imagined changes was measured by using a 2AFC adaptation method. They were unaware that the dummy loudspeaker was not active. In the SM condition, both the participant and the active loudspeaker were on the floor, while the dummy loudspeaker was on the swing. In the LM condition, the participant and active loudspeaker were placed on the swing and the dummy loudspeaker was at a fixed position on the floor. Thus, all stimuli were identical in both LM and SM conditions, except for vestibular cues. In limiting the study to approaching sounds, the sound was presented only when the participants moved forward in the LM condition or when the swing moved toward participants in the SM condition. Results showed that the perceived modulation amplitude was larger for sound source motion (SM) than the actual modulation level of the swing motion. These results suggest that self motion information from the vestibular system has an effect on the estimation of distance for approaching sound sources.