1979 年 35 巻 10 号 p. 569-576
Patterns of time series of sound levels observed every one second successively at the site near the traffic flow, can be represented by evaluation of probability density function and the transition probability density function of sound levels. A method of predicting these function from traffic volume, vehicle speed, percentage of heavy vehicles and the distance between traffic road and observation point, is discussed under following assumptions:1. Sound levels are observed at an equal time interval successively and are read in discrete integers. 2. Vehicle speed is constant during observation period. 3. Traffic is mono, lane, and consists of heavy and light vehicles. 4. Road is flat, and there are no buildings which prevent the sound propagations from the road to the observation point. 5. There is no branch extending over enough length on the road, and traffic is steady flow. 6. The ratio of the distance between traffic flow and observation point l to average vehicle spaces d is the 0. 46<l/d<1. 60. The parameters which need evaluating in the probability density functions, are the average relative sound level(The reference 0dB is the minimum sound level during the observation period. ), the relative maximum sound level, the probabilities in which the sound level decreases and increases by one dB respectively during two successive observations. The comparison between the measured values and the calculated ones shows good agreement.