Sound field reproduction system with active reverberation

Abstract

Sound field reproduction system can be categorized roughly into two types. The first is physically assured system which reproduce the wavefront or another physical parameters by engineering means. Typical examples are the boundary surface control system, the wave field synthesis, the ambisonics, and so on. The second type is a psychological system that reproduces phantom images one sound at any desired position by artificial manipulation with rather simple technique such as volume based amplitude panning. Examples are the two channel stereo system and the surround system using 5.1 or more loudspeakers. The latter can be recognized as somewhat “artistic” method, because it requires norms based on artistic sense. The present study aims to fuse the engineering and artistic systems mentioned above. The boundary surface control system, which consists of 24-channel narrow directional microphones and 24 channel loudspeakers, was used as the platform of research. Based on the conventional control technique using inverse filtering, additional manipulation such as simple reproduction scheme for high frequency was introduced. Also, the concept of variable reflection acoustic wall system, which adds the artificial reverberation to the sounds that listener makes, was involved in the reproduction system for the direction of the presence.