Many physical sound field synthesis techniques have been studied. To implement these techniques, a large-scale reproduction system is usually required with a large number of loudspeakers, D/A converters, and amplifiers. Thus, the techniques are not suitable for use in a rooms of an ordinary house. In our recent studies, a physical sound field reproduction system was developed with a digital loudspeaker array and suitable for an ordinary, small room. To more accurately reproduce the sound field with the implemented loudspeakers, an effective method is local sound field synthesis (LSFS). Because the area of the reproduced sound field is limited in LSFS, the reproduction area must track the listener's head movement. To track the listener's head movement, the driving functions of loudspeakers must be changed in real time. In this study, the effect of switching the reproduction area is investigated to determine the appropriate switching rate and size of the local area.