Abstract
The additive model with external fluctuation factors and the multiplicative model with internal fluctuation factors are well-known as two fundamental models describing the stationary and non-stationary random phenomena in the actual engineering field. An actual stochastic systems described by an additive model in a short time interval must be very often described in a long time interval by a mixed type stochastic model containing the fluctuation of multiplicative factor, because the internal parameter of the system changes with the passage of time. In this paper, first, by introducing a mixed type stochastic model for the actual random process, a unified expression is proposed for the probability distribution function of the above non-stationary composite wave measured by an arbitrary non-linear observation system. Next, by use of the above theory, two types of new methods identifying the probability distribution function of a specific factor embedded in the composite wave are derived in a general form of series expansion expression. Finally, by applying the above theoretical results to various types of L_<eq> evaluation problems of road traffic noises and industry noises based on the actual noise observations corrupted by the background noise, the validity of proposed evaluation methods is also experimentally confirmed.
