PURPOSE: To reproduce a sound field corresponding to diversified listeners' favorites by inputting one of both channel signals for a phase shift where a phase center frequency can be varied and set continuously and performing addition or subtraction between the output signal of the phase shift and the other channel signal.

CONSTITUTION: The phase shift 2 varies the phase of the input signal R from 0 to -π and the phase center frequency f0 can be varied and set continuously by a listener. When the phase center frequency f0 is set to a certain value F0 in an audible range, the output signal of the phase shift 2 varies from an R signal to the inverse of R signal according to the frequency of the R channel signal inputted to the phase shift 2. The listener varies and sets the frequency according to the listener's favorite, an adding circuit 3 outputs a sum signal component L+R, a difference signal L-R, and their intermediate signal component as a surround signal, and consequently the sound field can be reproduced according to the diversified listener's favorites.