Abstract:

A huge speaker array system of 128 loudspeakers was constructed and experimented. It was implemented as ``software-centered'' style, utilizing stock loudspeakers and a PC. No dedicated hardware nor DSP was utilized. Spot forming, instead of beam forming, could be realized by 32 by 4 square layout of the array. Spot means small area of higher sound pressure level. Number of the spot was not limited to one. In the experiment, within 3 m by 3 m area, four spots of different sounds could be simultaneously formed. This spot forming was confirmed by actually measuring spatial distribution of sound pressure level. The effect of the spot was also confirmed auditorily. Since the system was software centered, it was dynamic. By simply changing software parameters, the location of the spot can be easily moved even while the system is running. This movability of the spot was intended to be the basis for visual steering. To realize the system, a simultaneous 128-channel 14-bit DA converter PCI board was developed. The 44.1-KHz sampling rate was achieved by a 2.4-GHz Intel Xeon based PC utilizing the DA board and a real-time OS, named ART-Linux. Approximately 23-(mu)s loop could be realized by the software. It was the world's fastest software loop.