A STATISTICAL STUDY ON THE PREDICTION OF RANDOM NOISE FLUCTUATION AND THE MUTUAL RELATIONSHIP BETWEEN VARIOUS NOISE EVALUATION INDICES IN AN ACOUSTIC ENVIRONMENT

音環境の不規則騒音変動に関する予測と各種騒音評価量間の相互連関に関する統計的研究

三谷 康夫

Industrial growth carries with it an increasing environmental noise pollution problem. In order to evaluate quantitatively environmental random noise, many statistical noise descriptors (i.e., noise evaluation indices) are now being used. Percentile noise level Lx, equivalent noise level Leg, traffic noise index TNI and perceived noise level PNL are some examples. Almost all these statistical indices are obtained in relationship with the whole probability distribution of environmental random noise. Noise surveys have indicated that road traffic noise is a major component of environmental random noise. In this doctoral thesis, a statistical method for prediction of road traffic noise generated by actual traffic flow of an arbitrary non-Poisson type is first discussed for practical application. Paying attention to the fact that sound insulation barriers are very often constructed to produce attenuation of environmental random noise, a method for predicting the stochastic insulation effect of a sound insulation barrier is then discussed for the case of arbitrary probability distribution of random noise incident on the barrier. In addition, the mutual relationships between various types of statistical noise evaluation indices in relation to Lx and Leg, which play an important role in the field of noise evaluation and regulation problems, are discussed for the purpose of evaluating systematically real random noise. More specifically, a method for estimating an Leg evaluation index is proposed using the moment statistics of random noise fluctuation.

Next, a method for estimation of Leg is presented, using the known values of several specific Lx. A new trial estimating the original distribution form of random noise fluctuation is then presented using the known values of Leq and several specific Lx, and a specific on-line measurement system based on the above-mentioned estimation theory for Lx and Leq is constructed with the aid of a microcomputer by introducing an iterative process for extracting the moment statistics of random noise fluctuation. The theoretical approaches in this study are generally applicable to any kind of random phenomena. The theoretical results are experimentally confirmed by applying them to actually observed noise data.

建築学 [ 520 ]

英語

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広島大学