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.     

Street categorization for the estimation of day levels using short-term measurements

Day time noise level computation by traffic noise model requires realistic traffic data that is hardly ever available for every single street, therefore direct noise levels measurements may be the alternative. However, direct, continuous measurement of the day time noise level (equivalent level from 7 am to 7 pm) is an expensive strategy if a whole city must be assessed. To overcome this situation, short-term measurements of variable duration are often taken in order to estimate the day time noise level (L_d) because they are less expensive and resource demanding than continuous measurements over a whole day or more. From a set of continuous measurements over more than 48 h in 137 streets of nine different cities, the present work quantifies the error committed when using short-term noise measurements as a function of interval length measurement. To enhance estimation accuracy, both a street categorization and a temporal categorization have been attempted: in first place, it is found that the difference between the short-term noise level and L_d follows a different distribution for main roads than for ordinary streets, therefore the error committed depends on the street category. To be specific, when estimating L_d from a 15 min short time measurement the error committed would be ±2 dB with a percent population coverage of 90%, in the case of main streets and in the case of ordinary streets the same error range covers 72.5% of the population. In second place, if the measurement range time is restricted (temporal categorization) from 9 am to 1 pm and from 2 pm to 5 pm in the case of ordinary streets, the percent population coverage increases to 90% when the error range is ±3 dB. When referring to main streets, the measurement range of time is limited from 10 am to 5 pm to obtain an increase of 2% of the percent population coverage when the error is ±1 and ±2 dB.     

Effects of urban morphology on the traffic noise distribution through noise mapping: A comparative study between UK and China

Due to the rapid urban development and massive population increase in many eastern cities, the difference in urban density and morphology between typical western and eastern cities is becoming significant. This consequently makes the noise distribution in the eastern cities rather different from typical low density European cities. In this research, two representative cities with different urban densities, Greater Manchester in the UK and Wuhan in China, were selected, which have low and high average urban density respectively, and also have considerable differences in building form and traffic pattern. In the mean time, these two cities have similar urban scale and traffic amount. In each city, based on the urban morphological analyses considering urban land-use, building and road density, and noise source distribution, a number of typical urban areas, 500 * 500 m² each, were sampled. A noise-mapping software package was then used to generate generic noise maps, based on existing digital vector maps for terrain and building, and traffic data obtained by on-site measurements. The comparison results show that the average and minimum noise level in Greater Manchester samples is generally higher than that in Wuhan samples, while the maximum noise level in Wuhan samples is mostly higher. By developing a Matlab program, correlations have been analysed between noise distributions and the urban characteristics relating to urban density, such as the road and building coverage ratio. Overall, comparisons between these two typical cities have shown significant effects of urban morphology on the traffic noise distribution.     

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。     

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.     

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.     

Traffic noise spectrum analysis: Dynamic modeling vs. experimental observations

This paper compares two traffic representations for the assessment of urban noise frequency spectrum: (i) a static one, based on mean vehicle speeds and flow rates, (ii) a dynamic one, which considers vehicle interactions along the network. The two representations are compared on their suitability to match real on-field noise levels, recorded on a three lane quite busy street. Representation (i) fails in reproducing spectra envelopes that correspond to this site. In particular, it underestimates low frequencies, what can conceal the real impact of traffic flow on urban sound quality. Representation (ii) greatly improves estimation. It guarantees accurate environmental noise assessment, since it reproduces all traffic situations that are encountered in the site. Moreover, its 1s-based structure allows for the evaluation of spectra variations, with a good accuracy.     

Random telegraph signal noise simulation of decanano MOSFETs subject to atomic scale structure variation

As MOSFETs shrink into the decanano regime it is predicted that random telegraph signals (RTS), resulting from trapping events in defect states near the Si/SiO₂ interface, will significantly affect analogue and digital circuit performance. At these same scales, intrinsic parameter fluctuations introduced by atomic differences between devices will also be significant. In this work, a methodology based on 3D simulation is developed which can correctly model RTS noise in the time and frequency domain in the presence of random discrete dopants. The approach is illustrated with results obtained for 30×30  nm devices. We find that atomicity can significantly increase RTS magnitude in devices with particular doping configurations, and ensemble average RTS effects vary markedly from those predicted on an assumption of continuous doping.     

Measurement techniques of noise level in various urban scenarios. Day selection and representative period

This work summarizes several years of measurements of the main noise sources present in large populations, specially the noise produced by the traffic in the city of Valencia. The study includes one-week monitoring in the period between the years 2012 and 2014 in three different types of scenarios (heavy, medium and low traffic). The aim of this work is firstly to determine the most representative measurement day under several approaches related to the type of day (working day, non-working day or full week), and to the different periods throughout the day (night, day and evening).     

Sampling techniques for the estimation of the annual equivalent noise level under urban traffic conditions

This paper summarises 5 years of continuous noise measurements carried out at one of the most important squares in Valencia (Spain). The chosen square is a clear hotspot for traffic noise in a large city. The aim of this study is to determine the appropriate measuring time in order to obtain a 24-h noise level suitable to represent the annual equivalent level. Our findings allow us to reach a number of conclusions in terms of the most suitable urban traffic noise measurement techniques. A random day strategy for sampling is found to give a more accurate representation than a consecutive days strategy. If the sampling strategy involves measurements on randomly-chosen days, then at least 6 days should be used.     

Study on the relation between urban planning and noise level

Different streets of a city of Spain were randomly selected and analyzed, extracting 135 different urban variables. The urban variables were compared with measured noise levels, and the possible significance in the relationships among them was analyzed. From the variables with a significant correlation, a multiple regression model for urban traffic noise was developed, which allows explaining 63% of the variability of urban noise. In this regression model, only eight of the initial urban variables were included.     

Macroscopic modeling of urban traffic noise - influence of absorption and vehicle flow distribution

Prediction of noise levels at shielded positions in urban areas is more difficult than on exposed positions. At shielded positions, the predictions method must include multiple reflections, and many sources must be taken into account. Using numerical methods that solve the wave equation is possible, but very computationally heavy. Here two methods have been used, a very simplified ray model and a statistical model. The results show that concentrating the traffic and introducing absorption onto building façades will give lower levels at shielded positions.     

城市道路交通噪声烦恼度社会调查

本文以烦恼度为主观反应指标,采用三种5级程度衡量尺度,对西安市内三条主要干道和两类典型交叉口附近区域内的道路交通噪声进行了烦恼度问卷调查。此次调查针对人口统计学因素(性别、年龄、文化程度、身体健康状况)上的个体差异与等级描述词不同的程度尺度可能对道路交通噪声烦恼度调查结果的影响,以及特定路况条件下的噪声烦恼度与不同机动车辆的行驶噪声烦恼度展开了研究。通过对调查数据的分析处理,发现并初步总结出:与选取不同的烦恼度尺度相比,人口统计学因素对调查结果的影响更加显著;人口统计学因素与特定路况条件下的噪声烦恼度及不同机动车辆的行驶噪声烦恼度无明显相关;但不同机动车辆的行驶噪声烦恼度不同,实际研究中需对摩托车噪声加以重视并区别对待。     

Influence of vehicle noise emission directivity on sound level distribution in a canyon street. Part I: Simulation program test

Simulation programs may be useful tools for controlling an environmental noise. The computer simulation program PROP11 that enables predictions of the time-average sound level within an urban system is used here. A roadway as a noise source is represented by a sum of the sound exposures due to individual vehicle pass-bys. Different representations of equivalent point sources for various classes of vehicles are allowed including directivity characteristics other than omnidirectional. Propagation throughout an urban system contains multi-reflections from the walls and single and double diffraction at their edges. In this paper, the PROP11 program is used to predict the sound level between opposing façades of buildings in a canyon street. A multi-lane road is assumed to contain two classes of vehicles (light and heavy) ones. The equivalent source representing vehicles is defined by the source power spectrum, its position above the ground and directivity characteristics. The consequences of introducing equivalent source directivity are analyzed.     

Traffic noise reduction due to the porous road surface

Porous road surfaces reduce road traffic noise. A new method of noise reduction assessment is proposed. The noise generated by a few vehicles was measured two times: on an old surface with the dense asphalt and on a new surface with the porous asphalt. Subjective assessments of drive-by noise suggest that the sound exposure and the road surface coefficient can be used as the acoustical characteristics of a road surface. Their average values, with the average number of vehicles passing the receiver during a day or night, makes it possible to predict the equivalent continuous A-weighted sound pressure level for the new road surface. This is the main objective of this paper.     

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.     

Prediction of the sound field into high-rise building facades due to its balcony ceiling form

This study presents the acoustic performance off tall building facades closed to roadway due to one of balcony configurations, namely ceiling, with an inclined form in terms of traffic noise reduction. Three inclined angles are tested (5,10, and 15°) with different balcony depths by using a Pyramid Tracing model developed by A. Farina. The results in terms of A-weighted sound pressure level reduction are expressed in free field into the balcony back wall. The protection level, defined as the difference in noise levels before and after inserting the proposed balcony form, has been used to assess the reduction offered by that configuration. A maximum reduction due to using these forms is obtained at higher floors and at balcony of 2 m depths and more. As a consequence of simulation results, it is found that the prediction of protection levels from 10th to 15th floor can be calculated from an empirical equation.