a reverberation system produces reverberant sound supposed to be generated when sound emitted from a real sound source location inside a virtual acoustic room to be simulated is reflected by virtual room partitions surrounding the same , based on a set of stored impulse responses of reverberant sound actually or virtually observed at different observation positions in the vicinity of room partitions defining an actual or virtual model acoustic room . digital filters each convolute a source signal representing the emitted sound , using coefficient parameters representing the corresponding stored impulse response , to thereby synthesize a virtual reverberant sound signal at each of simulation positions corresponding to the observation positions . signal delay devices each delay the output of the corresponding digital filter , by a signal delay time controlled by a time delay setting device to thereby equivalently move the virtual room partition of the virtual acoustic room relative to the real sound source location , and hence virtually change the virtual acoustic room into a desired shape .