Sound field evaluation by using closely located four-point microphone method and mixed reality technology

The closely located four-point microphone method was proposed by Yamasaki in 1989. The method can grasp the spatial and temporal structures of sound reflections by estimating an image source distribution from four measured impulse responses. In recent years, mixed reality (MR) technology has rapidly developed and is now more familiar. Many sensors, display devices, and ICT technologies have been implemented in MR equipment, which enable interaction between real and virtual worlds. We proposed a MR display system for image source distributions and directivity patterns of sound reflections, which are obtained by the closely located four-point microphone method. In this paper, we propose a MR display system for some image source distributions measured at multiple measurement points. By moving in the room, the user can view the image source distribution in the room adjusting to the user's view point simultaneously. MR display enable us to observe the spatial and temporal structures of sound reflections in the room while maintaining a relationship between the positional information of the real room and the data, even when user moves around the room.