车辆声学当量折算系数研究

Study on the equivalent conversion coefficient of the vehicle acoustics

为在公路交通噪声预测时能同时考虑不同车型和同种车型车辆辐射噪声特性不同对预测结果的影响,提出了车辆声学当量折算系数的计算方法。以单车辐射噪声声压级模型为基础,利用噪声求和公式推导出具有任意速度的任意车型间的声学当量折算系数计算公式;对速度调查结果分析发现,自由流行驶状态下各种车型车辆速度均服从正态分布,利用此特点提出了速度离散化方法;以小型车为折算车型、小型车平均速度为折算速度,利用声学当量折算系数公式计算了哈双高速每种车型不同速度组车辆折算成具有平均速度的小型车当量数。通过该方法将具有不同速度的不同车型车辆折算成一定当量数的具有同一速度的小型车,总交通量被折算成辐射噪声水平相同的小型车当量交通量。

The present article is aimed at a study on the equivalent conversion coefficient of the vehicle acoustics in China by taking the traffic noise conversion and calculation as a study topic. As is known, traffic noise conversion and calculation used to be done by using the prediction model in ＂Specifications for the Environmental Impact Assessment of Highways,＂ whereas we know that its levels or grades and its equivalent conversion can be calculated in different ways through the equivalent conversion coefficient. However, the aforementioned model doesn＇t take into account the influential factors which may impact the speed of various types of vehicles in its predic- tion results. It is just starting from the need to discuss the impact of the noise characteristics of the various types of vehicles on the results of the highway traffic noise predictions that we have proposed a method for calculating the vehicle acoustics equivalent conversion co- efficient. What is more, we have also derived a formula for this pur- pose by using a noise summation formula based on the modet for cal- culating the single vehicle noise pressure levels. The speed survey re- sults and their analysis help us to find that the speed calculation for all types of vehicles has to follow the Gaussian distribution in the free traffic flow, which helps to propose a speed discretization method. Following this thinking line, we have chosen a small car as the tar- geted conversion vehicle type, with its average speed taken as the conversion speed. And, then, we have converted each type of vehi- cles into an equivalent number of small cars with the same speed moving by using the calculation formula of the above said acoustics e- quivalent conversion coefficient on the Harbin-Shuangyashan Express- way. The above said method helps various vehicles with different speeds turned into car equivalent numbers, whereas the total traffic volume can be converted into that of the passenger cars by comparing themselves with each other at the same noise levels. And, finally, it would be possible to establish the noise level model by using the con- vetted traffic volume and the qonverted speed rates within the ＂traffic noise prediction model, which can help to simplify the choice of the input variables by taking into account both the various vehicle types and the different speeds at the same time by using the acoustics e- quivalent conversion coefficient. Thus, it can be seen that this method is more convenient and effective in calculating the traffic noise level. Therefore, the paper has offered a new and better method for predicting the traffic noise.