2012 年 78 巻 786 号 p. 420-430
In this study, a virtual sound production system is developed where the difference frequency component appears as the secondary audible sound at a point of interference locally by the nonlinear interaction of two independently radiated ultrasounds while they travel directionally and intersect each other. The design of high-directive ultrasonic radiator, followed by the investigation of virtual sound production performance has been done theoretically as well as experimentally. It is known from these investigations that the fairly local sound reproduction in free space is possible, yet the sound pressure level of the secondary field is small. The results have also shown that the generated virtual sound area is dependent on both the difference frequency and the intersection angle of two carrier waves emitted by two sound sources.