公路交通噪声频率特征及等效频率研究

为了确定不同车型在不同行车速度下的噪声频率分布特性及等效频率值,更加准确的对交通噪声的影响进行评估,本文对单车稳态辐射噪声的频率特性进行了现场测定,并对不同类型车辆的频率特性数据进行了分析。结果表明,不同类型车辆车速与频带声压级之间的相关性随频带中心频率的变化而变化。FHWA模型对公路交通噪声中介于500 Hz～2000 Hz频段的噪声有较好的预测效果,而对低于500 Hz和高于2000 Hz的交通噪声的预测精度较差。车辆类型不同,车辆产生噪声的中心频率、声能量集中分布的频率范围以及等效频率均不相同。     

公路交通噪声等效车道距离的确定方法探讨

在公路交通噪声计算中,目前常用的确定等效车道距离的方法是计算接受点至近车道和远车道的距离的几何平均值,但使用该方法得到的接受点处的交通噪声与使用两个车道分别计算后再叠加的方法所得到结果相比,存在一定偏差。本文提出用调和平均值确定等效车道距离,即用接受点至近车道和远车道的距离的几何平均值的平方除以算术平均值来确定等效车道距离。通过比较,证明调和平均法比几何平均法具有更高的精确性。     

公路交通噪声阈限值的分析研究

本文采用客观测量和主观评价相结合的方法研究公路交通噪声对人的影响。通过研究,求得了公路交通噪声扰民的容忍阈值,分析了比较了公路交通噪声各种客观评价量与人的主观评价量的之间的相互关系。     

城市车辆流分布模型及道路交通噪声预报的研究

本文将道路中通行的各种车按其发出的噪声级的高低分成四个等级。提出以每小时900辆的车流量为限,车流将分别服从“泊松”及“正态”分布。对车流较大,服从“正态”分布车流。定量地分析出各等车流量与路边统计噪声级的关系,推导出相应的公式。与他人已做过“泊松”分布一起,构成一套完整的路边声级L_(10)预报表。可以做为评价、预测城市交通噪声之基础。经在北京多条道路的实测验证,与实测值很好符合。     

用Cadna/A软件预测桥梁交通噪声及应用分析

城市环境噪声的主要声源是车辆交通噪声,而城市高架道路经过区域的声环境影响比较复杂。城市高架桥路段两侧交通噪声排放主要在地面辅道和桥梁高架段,地面辅道交通噪声对临路第一排居民影响最大,而高架道路交通噪声对高层及后排居民的影响较大,范围更广。如何有效单独分析地面辅道交通噪声和桥梁高架交通噪声对周围环境的影响程度,将对交通噪声源的治理和对道路两侧不同范围内声功能区域建筑物的降噪措施提供理论依据。下面以上海沪闵路一沪杭公路地方越江大桥为例,分析了大桥的地面辅道和高架桥段敏感点的声环境现状,运用Cadna／A软件预测和分析越江大桥运营后地面辅道和桥梁高架段交通噪声各自对周围环境的影响,研究相关敏感地区的可能环境噪声状况,以及交通噪声影响的程度特征。     

换流变压器噪声预测模型及其简化研究

换流变压器作为高压直流换流站主要噪声源,其噪声预测精度和控制方法的选择将直接影响换流站整体噪声预测水平及治理效果。通过对换流变压器噪声的产生机理、噪声频谱及常见治理方案等方面进行系统研究,重点推出了换流变压器噪声控制方法BOX-IN技术,并就BOX-IN装置的噪声预测模型进行了简化和对比验证。通过对降噪量进行现场测试,结果表明,BOX-IN装置降噪量达到20dB(A)左右,与理论计算值近似,为进一步提高高压直流换流站噪声预测精度提供了理论依据。     

中国城市噪声的现状

本文为京津地区内大小城市的噪声调查报告。这个地区除北京和天津市外,还有22个县,人口共一千八百万。这里是中国的一个典型区域,从这调查结果可以了解中国城市噪声的一般情况,以及近十年一些技术措施和行政措施所得到的效果。     

基于两级通流模式的贯流风扇气动噪声模型

贯流风扇独特的流动形态导致主流并非发生于部分流道,根据其内流特点,本文提出了两级通流模式。在离心风扇及轴流风扇气动噪声模型基础之上,同时考虑风扇的具体几何尺寸,运行情况,及蜗壳的存在对噪声传播的影响,提出了贯流风扇叶轮气动噪声的预估模型。试验结果验证了该模型的可靠性,在低转速1100r/min以下时可以较好地预测贯流风扇的气动噪声总声压级,在较高转速时,存在一定的误差。     

考虑行驶状态的水泥路机动车噪声排放模型

本文旨在建立机动车单车辆的基础噪声排放模型,通过对大中小车辆在加速、减速、匀速及怠速状态下A计权声压级进行测量,运用回归分析方法拟合实验数据,得到考虑车型和行驶状态的水泥路面机动车单车辆噪声排放模型,并利用另一部分实测数据进行对比验证。误差分析显示:比较《公路建设项目环境影响评价规范(JTG B03-2006)》中的噪声模型,本研究建立的单车辆噪声排放模型预测精度更高。     

平交路口交通噪声的测量分析与模型计算结果

本文给出了对有交通控制信号的十字型平交路口,交通噪声（以下简称路口噪声）的测量及统计分析结果。指出用统计声级L₅₀和L₉₀来衡量时,路口噪声比所谓自由车流噪声要高出3—7dB（A）;而用L₁₀和等效声级L_eq的衡量时,两者几乎没有区别,虽然两者给人的感觉有所不同。通过与点声源路口噪声模型的计算结果对比,得出路口噪声统计声级L₅₀增高是因为两条道路相交,横路上车辆的运动噪声对总噪声能量的贡献。文中还讨论了路口噪声的统计分布和瞬时噪声级与交通控制信号之间的关系等问题。     

New vehicle noise emission for French traffic noise prediction

Traffic noise prediction models in France are based on vehicle noise emission values defined by the French Guide du Bruit des Transports Terrestres (Noise Guide for Ground Transport - Noise levels prediction). These emission values are suited for models addressing the noise assessments of road infrastructures and the dimensioning of acoustic protections, needing traffic noise estimations in terms of ?_Aeq over a long period of time (an hour or more).The values, obtained from measurements collected in the 70s, are updated in the publication of a new guide (Methodological Guide, Vehicle noise emissions, to be published), which addresses the road surface influence on tyre/road noise. The emission values are now expressed through the contributions of a power unit component, function of traffic speed, traffic flow type and road declivity, and of a rolling noise component, function of traffic speed and road pavement.The paper outlines the procedures followed to determine the components, gives their numerical values, and illustrates some vehicle noise emissions.     

Highway traffic noise prediction using method fully compliant with ISO 9613: comparison with measurements

In this study, we introduce outdoor sound simulation that is fully compliant with ISO 9613 yet with some complementary methods that enhance its applicability; for example, calculation of sound attenuation due to undulating terrain in octave bands, geometric divergence in the near-field of the source, and short-term wind effects. Using the method, we have carried out highway traffic noise prediction and measurement for 12 sites with representative road shapes and structures. In the prediction, the sound power level for a road segment was estimated by the method suggested in ASJ Model-1998 with experimental corrections to the overall noise level and spectrum. Comparing results between predicted and measured noise levels show good correspondence at direct, diffracted and reflected sound fields within 30m from the center of the near side lane.     

Estimation of the long term average sound level from hourly average sound levels

It is shown how to estimate the long-term average sound level, L_AeqLT (for free flowing road traffic) from measurements of the hourly A-weighted equivalent sound level, L_Aeq1h. To estimate the parameters of the model which describe noise emission and attenuation, concurrent measurements of L_Aeq1h at two distances from the considered road are needed. A semi-empirical formula is derived for L_AeqLT approximation. Also the uncertainty of this approximation is given as a function the distance from the road and receiver height.     

Estimating traffic noise for inclined roads with freely flowing traffic

Traffic noise measurements on the kerbs of 19 independent inclined trunk roads with freely flowing traffic within the residential areas of Hong Kong are carried out in the present investigation. The performance of the existing noise prediction models in predicting traffic noise from inclined roads is evaluated. By regression analysis and simple physical consideration of the traffic noise production mechanisms, formulae for the prediction of the L_A10, L_A50, L_A90 and L_Aeq are developed or re-calibrated. Results suggest tyre noise has the major contribution to the overall noise environment when the source is an inclined trunk road. Also, the road gradient is found to have a higher contribution to the traffic noise than assumed in the existing models, but becomes unimportant when the background noise level L_A90 is concerned.     

Honking noise corrections for traffic noise prediction models in heterogeneous traffic conditions like India

In developing countries like India, the nature of the composition of traffic is heterogeneous. A heterogeneous traffic flow consists of vehicles that have different sizes, speeds, vehicle spacing and operating characteristics. As a result of the widely varying speeds, vehicular dimensions, lack of lane disciplines, honking becomes inevitable. In addition, it changes the urban soundscape of developing countries. In heterogeneous traffic conditions, horn events increase noise level (L_den) by 0.5–13 dB(A) as compared to homogenous traffic conditions. Therefore, the traffic prediction models that are used for homogenous traffic conditions are not applicable in heterogeneous traffic conditions. To increase the accuracy of noise prediction models, in depth understanding of heterogeneous traffic noise is required. Understanding the real traffic noise characteristics requires quantification of some of the basic traffic flow characteristics such as speed, flow, Level Of Service (LOS) and density. In a given roadway, the noise level changes with density and LOS on the road. In this paper, a new factor for horn correction is introduced with respect of Level Of Service (LOS). The horn correction values can be incorporated in traffic noise models such as CRTN, FHWA, and RLS 90, while evaluating heterogeneous traffic conditions.     

Analysis of the prediction capacity of a categorization method for urban noise assessment

A street categorization method to study urban noise was tested by comparing its results and predictive capacity with those of a reference method – the standard grid method (mentioned in the ISO 1996 standard). To this end, two independent noise surveys were carried out simultaneously in the city of Cáceres (Spain), each using one of these two methods. In a first step, the overall values of each procedure were obtained and the differences analyzed. Then, to analyze the predictive capacity of the categorization method, the two noise maps were constructed, and their predicted values (the noise levels of the squares of the grid for the grid method, and of the categories for the categorization method) were compared with the data of the other procedure used as control.It was found that the categorization method yielded similar results for the overall analysis of the city to those obtained with the value of the points of the grid method with considerably fewer sampling points.The categorization method also seems to be a more suitable predictor for new measurements, particularly for levels in the noisiest streets of the town.     

Prediction feedback in intelligent traffic systems

The optimal information feedback has a significant effect on many socioeconomic systems like stock market and traffic systems aiming to make full use of resources. In this paper, we studied dynamics of traffic flow with real-time information provided and the influence of a feedback strategy named prediction feedback strategy is introduced, based on a two-route scenario in which dynamic information can be generated and displayed on the board to guide road users to make a choice. Our model incorporates the effects of adaptability into the cellular automaton models of traffic flow and simulation results adopting this optimal information feedback strategy have demonstrated high efficiency in controlling spatial distribution of traffic patterns compared with the other three information feedback strategies, i.e., vehicle number and flux.     

Motorway noise modelling based on perpendicular propagation analysis of traffic noise

A model for motorway traffic noise has been obtained from measurements along the the Bangkok-Chonburi motorway. The model’s parameters include traffic volume and combination, the average spot speed of each type of vehicle and the physical conditions of the motorway in terms of right-of-way width, number of lanes, lane width, shoulder width, and median width for both of the main carriageways and frontage roads. The noise level that is generated by each type of vehicle has been analyzed according to the propagation in the direction perpendicular to the center line of motorway’s carriageway. The total traffic noise is then analyzed from traffic volume of all vehicle types on both sides of carriageways and frontage roads. The basic noise levels used in the motorway traffic noise model are modified according to the effective ground effect along the propagation path. The final result of this study is that a motorway traffic noise model based on the perpendicular propagation analysis technique performs well in a statistical goodness-of-fit test against the field data, and therefore, can be used effectively in traffic noise prediction for related or similar motorway projects.