Matsushita Commun. Indust. Co., Eng. Div., 600 Saedo Midoriku, Yokohama 226, Japan
A localization of moving reinforced sound source is described. A sound reinforcement system, in which microphones and loudspeakers are installed in the same sound field such as a conference room, has a drawback of insufficient reproduced sound pressure due to an adjustment to prevent howling. The fundamental technique of howling suppression that decreases coupling between microphones and loudspeakers is well known. The algorithm for decreasing coupling proposed here is based on a synthesis of directivity of microphone arrays to meet its dips in the directions of loudspeakers automatically. The direction of loudspeaker includes not only direct propagation but propagation through reflection and diffraction. In order to localize the direction in real time, a reference signal that is superposed on the speech signal is continuously detected by microphone. As a result, the reference signal whose sound pressure is low enough to be the same as the room noise of a typical broadcasting studio, will be detected without interference for speech communication by using spread spectrum technology.