A traffic noise model for road intersections in the city of Cartagena de Indias,Colombia

Road traffic noise models are fundamental tools for designing and implementing appropriate prevention plans to minimize and control noise levels in urban areas. The objective of this study is to develop a traffic noise model to simulate the average equivalent sound pressure level at road intersections based on traffic flow and site characteristics, in the city of Cartagena de Indias (Cartagena), Colombia. Motorcycles are included as an additional vehicle category since they represent more than 30% of the total traffic flow and a distinctive source of noise that needs to be characterized. Noise measurements are collected using a sound level meter Type II. The data analysis leads to the development of noise maps and a general mathematical model for the city of Cartagena, Colombia, which correlates the sound levels as a function of vehicle flow within road intersections. The highest noise levels were 79.7 dB(A) for the road intersection María Auxiliadora during the week (business days) and 77.7 dB(A) for the road intersection India Catalina during weekends (non-business days). Although traffic and noise are naturally related, the intersections with higher vehicle flow did not have the highest noise levels. The roadway noise for these intersections in the city of Cartagena exceeds current limit standards. The roadway noise model is able to satisfactorily predict noise emissions for road intersections in the city of Cartagena, Colombia.     

Neural based contingent valuation of road traffic noise

In this paper, we present a new approach to value the willingness to pay to reduce road noise annoyance using an artificial neural network ensemble. The model predicts, with precision and accuracy, a range for willingness to pay from subjective assessments of noise, a modelled noise exposure level, and both demographic and socio-economic conditions. The results were compared to an ordered probit econometric model in terms of the performance mean relative error and obtained 85.7% better accuracy. The results of this study show that the applied methodology allows the model to reach an adequate generalisation level, and can be applicable as a tool for determining the cost of transportation noise in order to obtain financial resources for action plans.     

某城市客车车内噪声试验与治理

针对某10 m城市客车车内噪声问题,根据相关标准进行摸底测试分析,在不改变客车本体结构的基础上,通过对车厢、发动机舱等部位进行合理的降噪处理,使得整车车内噪声等级由普通级提升到中级。     

发动机油轨脉动噪声的仿真与试验研究

针对某乘用车开发过程中出现的怠速低频噪声进行了研究,发现噪声源为汽油机喷油器反复开启产生的燃油压力脉动。应用商业流体软件对喷油器关闭瞬间燃油在油轨内的传播过程进行三维仿真,得到油轨内的油压变化规律。并在原机模型的基础上分析了油轨尺寸和横截面积的变化对油压的影响。分析表明:油轨横截面面积加大对油压脉动有一定的降低作用;相同横截面积条件下,长宽比越大,抑制油压脉动的效果越好。优化方案的噪声测试结果表明,方轨比圆轨的噪声小,但圆轨带内置缓冲器,效果最佳,可降低车内噪声3.2dB。     

基于无限元方法预报非均匀流中螺旋桨的流噪声

为了系统地研究非均匀流场中螺旋桨流噪声的特点,采用CFD与声学无限元方法结合的方式,对螺旋桨的频域噪声进行数值预报。通过采用大涡模拟方法对非均匀流场中的螺旋桨水动力性能进行计算,然后运用ACTRAN软件的声学无限元方法,对螺旋桨的无空泡噪声进行数值模拟,并对特征点进行频域分析。流场计算结果显示:非定常计算得到的螺旋桨水动力系数与试验值吻合良好,LES模拟得到的流场初值是可信的;通过分析噪声分布云图及特征点频谱曲线得出:非均匀流场中螺旋桨的辐射噪声主要集中在低频段,且该频段的噪声主要由偶极子组成,同时噪声衰减速度随频率增大而减小,螺旋桨轴向声压级高于径向两侧,验证了计算结果的可靠性,为螺旋桨的水下噪声预报提供了一种新的方法。     

基于Lighthill声类比理论的螺旋桨噪声性能研究

论文基于Lighthill声类比理论和傅立叶变换结合声学软件Actran开展螺旋桨噪声性能的分析研究。以E779A螺旋桨模型为对象,进行了螺旋桨噪声性能的数值模拟,分析了不同位置处声压谱和声功率谱的特性、噪声随距离变化的衰减特性、不同进速系数下的声压级云图等;最后,分析了非均匀进流、螺旋桨空化、进速系数等对螺旋桨噪声的影响。本文主要的研究工作是对螺旋桨噪声性能的预报研究,对今后船舶工程螺旋桨的设计研究有着重要的指导意义。     

大型深水物探船船型研究

介绍国际上大型物探船的船型发展情况及其主要作业特点。结合我国近年新建的大型物探船,分析该船型在总布置、性能指标、谐波控制、水下噪声等方面的技术难点。     

沥青混凝土路面噪音产生机理与影响因素分析

首先从轮胎振动、空气泵效应、空气扰动、滑-粘效应等方面分析了轮胎和路面噪音产生机理,并从号筒效应和腔体共振效应两方面分析噪音增强机理,然后分析了噪音的影响因素。结果表明:不同类型的沥青混合料对噪声吸收程度影响较大;混合料孔隙率越大,对噪音的吸收效果越好;大粒径沥青混合料对高频率噪声吸收效果好,小粒径与之相反。     

片状Fe-Si-Al-Cr磁粉复合材料的传导噪声抑制特性研究

通过压延工艺制备了含有片状Fe-Si-Al-Cr合金磁粉的电磁噪声抑制片,采用微带线法表征了样品的传导噪声抑制特性,并研究了磁粉填充浓度和样品厚度对噪声抑制特性的影响。结果表明:材料的传导噪声抑制特性随着磁粉填充浓度或样品厚度的增加而提高,其中填充浓度为85%(质量分数)厚度为1mm的样品在1.86~6 GHz范围内功率损耗比高达90%以上,显示出优异的噪声抑制性能。     

基于小波变换的雷达图像处理技术及仿真

在现代船舶中,航海雷达广泛应用于航海导航、目标物检测跟踪及安全运行等领域,所以在船舶中配备实时高效的雷达数据及图像处理系统成为利用航海雷达的关键。同时,小波变换由于其具有高分辨率的图像处理功能而在图像处理领域得到了较为深入的研究应用。本文研究航海雷达图像信息中混入噪声及杂波的分布特性,提出一种基于小波变换的雷达图像数据杂波抑制、去除噪声的方法,最后给出仿真结果并进行分析。