The aim of this study is to develop a simple personal computer-based sound reproduction system for audiovisual systems with high immersion. Conventional systems for providing high-presence sound have the disadvantage of requiring powerful computers. To simplify such systems, we propose a method for reducing the amount of processing required for moving sound images. In the proposed method, moving sound images are given as combinations of discrete coordinates. When visual and auditory stimuli are shown simultaneously, a ventriloquist effect occurs, causing moving sound images with discrete coordinates to be perceived as natural. Previous studies have clarified the conditions under which the ventriloquist effect occurs for a fixed sound image. However, the conditions under which this effect occurs for moving sound images remain unclear. We conducted an experiment comparing pairs of stimuli to evaluate synchronization of a moving sound and image. In the experiment, moving sound sources with different presentation times were compared to obtain an upper limit on the distance between discrete coordinates of moving sound images that are perceived as natural. We analyzed the relationship between synchroniza-tion score and presentation time by a paired comparison method, and found that the score de-pended on the presentation time of the sound image. This indicates that, for moving sound imag-es to be perceived as natural, the upper limit on the distance between discrete coordinates de-pends on presentation time.