Abstract— This paper describes 3D sound field generation by multiple lines speaker array. In order to realize a novel hands-free sound interface for human-machine systems, the authors are studying multiple lines speaker array. A technique to transmit sound towards a specified direction by speaker array of one straight line is known as beam forming. The authors propose an idea that two and three orthogonal lines speaker array can form spot-like small area of higher sound pressure level. We conduct simulation of two and three lines speaker array. Simulation results support feasibility of the idea. Based upon the results, the authors construct 32 by 2 lines array and 32 by 3 lines array. And we actually measure 3D distribution of sound pressure level by the constructed arrays. Results of the measurement also support the feasibility of our idea. I. INTRODUCTION HIS paper presents a basic investigation of novel hands free sound interface for man-machine symbiotic systems. To expand application field of the human-machine systems and bridge so called digital-divide, more natural, intuitive, comfortable and easy interface for the system is demanded and awaited. Thus the authors are developing hands free sound interface that is possible to form a spot-like small area of high sound pressure level at the desired location in the space by utilizing speaker array. We intend this hands free sound interface to be used in HAL9000-like intelligent environment systems, such as AIRE, Robotic Room, Enabling Environment, and so forth[1]-[14]. The speaker array of one straight line is possible to selectively transmit sound towards a desired direction by properly adjusting delay to signals for each elements of the array. A beam of high sound pressure level is formed from the array to the direction. This effect is know as Beam Forming and the mechanism is also known as SDBF (Sum and Delay Beam Former) [15]. But the term of "beam" is Manuscript received March 8, 2005. F. K. Sakaya is with Tokyo University of Science, Chiba, 278-8510 Japan (e-mail: j7504620@ed.noda.tus.ac.jp). two dimensional. From the viewpoint of 3D space, distribution of the high sound pressure level can be said as wall. Beam is contour on the cross section at one height. Only the direction can be controlled and thus it is 1D from the viewpoint of controllability. To enhance locality of the high sound pressure level area and make the area spot-like, the authors have studied two lines speaker array [16]. From the viewpoint of 3D space, the two lines array can generate cylindrical distribution of the high sound pressure. Contour of the cross section is circular spot. Thus the location of the cylinder can be controlled in 2D. In other words, the sound spot formed by the two lines speaker array is two-dimensional. It means that the two lines array cannot control height of the spot. Fig. 1 Effects of height controllability of sound spot In this paper, to remove the restriction and to enable the speaker array to control height of the spot, the authors extend the array to three orthogonal lines. Figure 1 illustrates effect of the height controllability of sound spot by the three lines array. It can transmit different sound contents to a sitting person, a standing adult and a child simultaneously. From the simulation on three lines array, we confirm possibility that spherical distribution of the high sound pressure can be formed. This is 3D sound spot. Based upon the simulation result, the authors construct the three lines speaker array. And utilizing the constructed array, we succeed to actually measure the spatial distribution of high sound pressure level. The measurement is conducted in 3D. The spherical distribution by the three lines array can be observed and confirmed. The measurement result is also confirmed 3D “Sound Spot” Forming by Multi Axis Speaker Array for Environmental Robot First K. Sakaya, Second H. Mizoguchi, Third T. Toba, and Fourth K. Kagami T Proceedings of the 2005 IEEE/ASME International Conference on Advanced Intelligent Mechatronics Monterey, California, USA, 24-28 July, 2005 0-7803-9046-6/05/$20.00 ©2005 IEEE. MB2-05 170