A probabilistic evaluation-method for the transmitted fluctuation of a sound insulation system directly connected with the internal mechanism of input noise and sound level meter.

Abstract

In this paper, a new trial of stochastic evaluation problem on the output sound level fluctuation of a sound insulation system with Gaussian random wave excitation is pro posedby considering the internal mechanism based on a frequency transfer character of insulation system and a mean-squaring operation of the sound level meter. The charac teristicfunction for the response probability of the sound level meter is derived first by employing the Parseval's complete relation. More concretely, an explicit expression of the output level probability distribution is theoretically given in a general expansion form by applying a well-known residue theorem in the theory of functions. Then, the output response probability function of the sound insulation system can be predicted by using the frequency spectrum of input random noise, the frequency transfer character of the noise insulation system and the measurement mechanism. Finally, the theoretically predicted results are compared with the experimentally observed results using a usual sound level meter for two kinds of single wall inserted between two reberveration rooms.