Up to now, many kinds of approaches on the prediction problem of road traffic noise were considered especially from the static viewpoint based on the internal physical mechanism of vehicles situation and sound propagation enviroment. However, its prediction method had to be very often changed when the above internal mechanism was changed, since this method is closely connected with the distinctiveness of vehicles and propagation situation. In this paper, strikingly differing from the previous method, a practical hybrid method between experiment and theory for predicting the level distribution of road traffic noise, applicable under an arbitrary types of vehicles situation and propagation environment, is newly proposed from some dynamical viewpoint of filtered Poisson process model. This functional prediction method has a character with no necessity based on the distinctiveness of vehicles and propagation conditions. Finally, the effectiveness of the present method is experimentally confirmed by applying it to the actual road traffic noise with a complicated situation of traffic flow below 1000 vehicle number/hr which can not be predicted by the well-known standard prediction method proposed by Acoust. Soc. of Japan.
Survey of personal noise exposure and response to noise environments in daily life of 142 workers has been done in and near Nagoya city. In this paper, the relationships between response of workers to their acoustical environments and various factors such as age, sex, occupation, noise exposure in each place(L_<eq>)and so on, are discussed. The response and other variables(i. e. factors)are properly categoralized and analyzed by quantification theory(type II and III). The results obtained are as follows;(1)Response to noise in workshop is strongly correlated to L_<eq>(noise exposure during work)and occupation(contents of work). (2)Response to noise during commuting is closely related to the means of commutation and is severe to public transportation(subway, train, and bus). (3)Response to noise in residence is considerably effected by type of housing, member of family and area of residence. (4)The significant factors to determine the response to noise around residence are conditions of road and areas near by house. (5)There are close cnnection between occupation and acostical environment in daily life of workers. (6)Response to noise is severe in elder generation and female in general.
In the practical engineering field of environmental noise and vibration control, there arises commonly the problem of detecting or evaluating a noise fluctuation emitted from a specific noise source under the actual situation when various other noise sources coexist. Hereupon, it is generally impossible to directly measure only a noise fluctuation from a specific source, and so it is necessary to satistically evaluate only a specific noise through the observation of composite noise. In this paper, first, by introducing an additive model for the actual stochastic process, a unified expression is proposed for the probability distribution function of the above composite wave measured by an arbitrary non-linear observation system. Next, by use of the above theoretical result, two types of new methods of identifying the probability distribution function of a specific noise embedded in the composite noise are derived in a general form of series expansion expression. Finally, by applying the above theoretical results to the evaluation problem of road traffic noise based on the actual noise observations corrupted by the industry noise and to its opposite case, the validity of proposed evaluation methods is also experimentally confirmed.
Ten young students with normal hearing acuity were exposed to white noise band-pass-filtered from 0. 9kHz to 9kHz for 24 hours in a reverberant room. Sound pressure levels of the exposure noise were 65, 70, 75, 80, 83 and 86dB. Thresholds of hearing at 2, 3, 4, 6 and 8kHz were measured before exposure, at some given time during the course of the exposure and after the exposure. Thresholds were also measured without noise exposure for 24 hours in the same way as was done with exposure to noise. The results showed that no significant threshold shift was observed when the subjects were not exposed to noise and that significant threshold shift was observed at all the levels of exposure noise when they were exposed to noise. Time after onset at which the temporary threshould shift (TTS) reached an asymptotic level ranged from 1. 6h to 46h. The asymptotic levels at 3, 4, 6 and 8kHz of the test frequencies were 4. 4, 3. 7, 8. 2 and 4. 2dB, respectively, when the exposure level was 65 dB and 14. 3, 21. 6, 21. 8 and 17. 6dB when it was 86dB. Linear relation between the asymptotic threshould shift and the exposure level was found and the slopes of the line were 0. 55, 1. 1, 1. 0 and 0. 81dB/dB for the test frequencies of 3, 4, 6 and 8kHz.