In this system, a terminal A retrieves terminal's input delay time Tia from input of an audio signal to start of transmission of the audio signal, transmission delay time Tn from the start of transmission of the audio signal to reception of the audio signal by a partner terminal B, partner's reception buffering delay time Tbfb from reception of the audio signal to output of the audio signal by a reception buffer portion BFb of the partner terminal B, and partner's output delay time Tob from input of the audio signal to output of the audio signal by an audio reproduction portion DRob of the partner terminal B. The terminal A then sums up these delay times to determine input/output delay time Ttab from the input of the audio signal by the terminal A to the output of the audio signal by the audio reproduction portion DRob of the partner terminal B.