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.     

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.     

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.     

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.     

公路交通噪声预测模型探讨

对公路交通噪声预测模型进行了分析推导,指出美国联邦公路局FHWA模型为近似表达式,并给出了精确表达式。对FHWA模型与精确表达式在硬地面、软地面、混合地面几种条件下的值进行了比较分析。结果表明,两者在硬地面条件下的形式和计算结果相同;在混合地面,即公路的实际情况下,两者存在差异,差值等于10lg(r1/r0)α。在用于高速公路交通噪声预测计算时,当r0取15m,该差值较小,当r0取7.5m,该差值增大;在一般情况下,r0取15m时的差值为±0.3dB(A),r0取7.5m时的差值为1.2—1.8dB(A),后者约占交通噪声预测值的1.5-4%,是不应忽视的。说明我国在引用FHWA模型时,对参考点距离的更改,会造成用于高速公路交通噪声预测的误差增大。建议我国使用本文推导给出的修订模型。     

考虑加速度的交通噪声源强研究

本文为研究机动车噪声源强与速度、加速度的关系,对车辆在不同速度和加速度下的A计权声压级进行测试,运用统计学方法对测试数据进行分析,得到机动车单车噪声源强与车辆速度、加速度的关系模型,并与《公路建设项目环境影响评价规范(JTG B03-2006)》中的交通噪声源强预测模型进行比较,实测验证结果表明,利用本研究建立的机动车单车噪声源强模型所得预测结果更符合实际。     

Variability in road traffic noise levels

Environmental noise levels can vary over a wide range as a result of the diversity of site conditions and activities occurring during field measurements. This variability, extremely important for a correct measurement interpretation, is often a source of disagreement when applying standards and regulations, as there is no consensus about how to estimate and present it. The paper contributes to this technical debate by investigating the statistical variability associated with a large measurement database acquired under field conditions. The database consists of 2 week’s noise recordings at each of 50 separate locations in residential areas affected mainly by road traffic noise. The results show increased variability (standard deviations) at the lower values of either logarithmic or arithmetic mean L_Aeq over the time periods investigated. It is anticipated that the observed relationships may be of assistance when estimating the noise level variability and the uncertainty associated with a noise measurement affected by road traffic or other environmental noise sources.     

Effects of traffic noise on paserine populations in Mediterranean wooded pastures

The effect of traffic noise on the breeding density of 20 passerine species was examined over a 2-year period in three different road types passing through pasture-woodlands in western-central Spain. No statistically significant differences were observed during the 2 years studied. An average of 19.6 birds/10 ha was recorded for the low-traffic road (LT), 21.7 birds/10 ha for the medium-traffic road (MT) and 19.1 birds/10 ha for the high-traffic road (HT). A total of 11 species (55%) did not show any statistically significant differences in breeding density among the different types of roads. By contrast, other species, such as the Blackbird, the Iberian Shrike and the Linnet, did point to differences between the MT and HT roads. House and Rock Sparrows, as well as the Corn Bunting, showed higher breeding densities near the HT road. The opposite effect was observed for the Wheatear, the Iberian chiffchaff and the Woodlark, for which high breeding densities were recorded in the vicinity of the LT road. Our results suggest that traffic noise constitutes a serious problem for at least 15% of the breeding bird community.     

Estimation of increases in noise levels due to installation of transverse rumble strips on urban roads

Increases in noise due to the installation of transverse rumble strips were investigated, by first measuring noise due single vehicles crossing a pilot test field with and without a rumble strip. After that, a procedure was proposed and carried out to estimate increases in noise due to the traffic of vehicles, based on the measurements previously mentioned. This procedure was checked against expressions from the literature that estimate traffic noise as well as measurements in three arterial urban roads without rumble strips installed. Its accuracy was compatible with the ones obtained by applying the literature expressions, the errors lying below 3 dB(A). Then, by taking the aforementioned roads as case studies, estimations were carried out for the increases that would occur in noise levels if rumble strips were installed on them, leading to values between 6 and 7 dB(A). Although such values are dependent on the configuration of the rumble strip employed, the proposed procedure presents generality and could be applied to estimate increases in traffic noise due to installation of rumble strips, by departing from measurements of noise due to single vehicles obtained for a given rumble strip configuration.     

Investigation on the intensity noise characteristics of the semiconductor ring laser

Based on the frequency-domain multimode theoretical model, detailed investigations on the noise characteristic of the semiconductor ring laser （SRL） are first performed in this paper. The comprehensive nonlinear terms related to the third order nonlinear susceptibility Z3 are included in this model; the Langevin noise sources for electric field and carrier density fluctuations are also taken into account. As the injection current increases, the SRL may present several operation regimes. Remarkable and unusual low frequency noise enhancement in the form of a broad low frequency tail extending all the way to the relaxation oscillation peak is observed in any of the operation regimes of SRLs. The influences of the backscattering coefficient on the relative intensity noise （RIN） spectrum in typical operation regimes are investigated in detail.     

Routing in scale-free networks based on expanding betweenness centrality

In this paper, an improved routing strategy is proposed for enhancing the traffic capacity of scale-free networks. Instead of using the information of degree and betweenness centrality, the new algorithm is derived on the basis of the expanding betweenness centrality of nodes, which gives an estimate of the traffic handled by the vertex for a certain route set. Since the nodes with large betweenness centrality are more susceptible to traffic congestion, the traffic can be improved by redistributing traffic loads from nodes with large betweenness centrality to nodes with small betweenness centrality in the process of computing the collective routing table. Comparing with results of previous routing strategies, it is shown that the present improved routing performs more effectively.     

A simple formula for evaluating the acoustic effect of balconies in protecting dwellings against road traffic noise

This study explores the noise reducing effect of a balcony and describes the development of a simple theory pertaining to the propagation of traffic noise from a road into a balcony. A new methodology is proposed that is based on the well-known prediction scheme—“Calculation of Road Traffic Noise” (CRTN)—developed in the UK. A geometrical ray theory is developed for the prediction of noise levels inside a balcony due to road traffic. The source level of road traffic noise is obtained as per the standard CRTN methodology. However, road sub-segmentations and new approaches for the prediction of noise levels at illuminated and shadow zones inside a balcony are proposed. Field measurements have been conducted on four different types of balcony to validate the proposed methodology. The insertion loss, defined as the difference in the noise levels with and without the presence of a balcony, has been used to assess the shielding effectiveness of a balcony against road traffic noise. The simple theory is validated by outdoor field measurements. It is also found that a properly designed balcony can provide considerable screening effects in protecting dwellings against road traffic noise.     

Evaluation and analysis of traffic noise from the main urban roads in Beijing

Traffic noise surveying and analysis was performed along three main roads in the Beijing urban area—the 2nd and 3rd ring roads circling the central downtown area and Chang-An Avenue, a major east—west corridor road through the heart of the city. The results indicate that these main roads are overloaded by traffic flow during daytime and noise levels due to road traffic along these roads are above relevant environmental standards by 5 dBA. The spatial variance of traffic noise was also analyzed, with the results indicating that the spatial differences result primarily from the unbalanced development of Beijing's urban districts.     

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。     

Blind separation to improve classification of traffic noise

In order to apply noise mapping to traffic noise prediction, a knowledge of several information about traffic characteristics is required to predict the noise levels emitted by the roads involved. In the European case, the CNOSSOS-EU calculation method for traffic-noise level prediction is now under discussion, to be agreed in response to the European Directive relating to the Assessment and Management of Environmental Noise (2002/49/EC). In this application context, standard ISO 1996-2:2007 Determination of Environmental Noise Levels, in its Section 6.2, specifically mentions that during L_eq measurements of road traffic noise the number of vehicle pass-bys shall be counted during the measurement time interval. This information is often not available in many roads, so it is typically registered by means of casual counts, often through manual procedures. Besides, if the measurement result is converted to other traffic conditions, a categorization of the vehicles involved is also required. Some additional information, such as the traffic density and the average speed, should be registered if a calculation method is used to build a noise map.In this paper a new automatic classification system of traffic noise covering these requirements is presented. The portable system processes a two channel audio recording to provide information of the average speed and the number of vehicles, which are classified in six categories during the measurement period. After several evaluations of the possibilities to get a good classification of the noise emission of a road from audio recordings, it is shown that increasing the within-class separation, as well as introducing a novel BSS–PCA-based classifier, the precision achieved in the final results is substantially improved.     

Property prices in urban areas affected by road traffic noise

This paper reports a revealed preference study into the different effects of road traffic noise on property values in residential areas with similarly high road traffic sound levels but with what appear to be important differences in the market for different types of residential property in each area. The results show significant differences in the revealed effects of noise on property prices between the three areas with in one case an increasing (and possibly misleading) relationship between higher monetary values and higher sound levels. A number of possible explanations for the findings are discussed in the paper.     

Dynamics of traffic flows on crossing roads induced by real-time information

Traffic flows on crossing roads with an information board installed at the intersection have been simulated by a cellular automaton model. In the model, drivers have to enter the road with a shorter trip-time indicated on the information board, by making a turn at the intersection if necessary. The movement of drivers induces various traffic states, which are classified into six phases as a function of the car density. The dynamics of the traffic is expressed as the return map in the density–flow space, and analyzed on the basis of the car configuration on the roads.