In direct connection with the signal information processing, a practical method of identification and probabilistic prediction for sound insulation systems is theoretically proposed in the object-oriented expression forms by introducing a few functional system parameters. Concretely, a trial of identification of the above functional system parameters and the output probabilistic prediction for a panel thickness change of double-wall type sound insulation system, especially, under the existence of a strong background noise inside of the reception room, is newly proposed based on one of wide sense digital filters and SEA (Statistical Energy Analysis) method. Finally, by using the actual music sound of an arbitrary distribution type, the effectiveness of the proposad method is confirmed experimentally by applying it to some problems of predicting the cumulative probability distribution of the transmitted sound level fluctuation.