Noise emission assessment of a hybrid electric mid-size truck

In the attempt to improve urban environmental conditions, city or national incentives encourage the use of cleaner vehicles, including hybrid electric vehicles. This paper explores the actual noise impact of this alternative drivetrain technology on the noise emission of a mid-size delivery truck powered by a parallel hybrid powertrain, compared with an equivalent internal combustion engine truck on the basis of pass-by noise measurements. It investigates jointly the overall emission, the main noise sources and the vertical directivity of the vehicle. The essential benefit results from the existence of a full-electric mode below 50 km/h, with a significant noise reduction which may exceed 8 dB(A) at low constant speed. Even if smaller, this noise advantage is still valuable when the vehicle is accelerating or braking. Due to weaker noise emitted upwards, the benefit should be even greater for residents living on upper building floors. The rolling noise associated with the drive wheel/road contact is the main noise source in all driving situations in electric mode, and beyond 50 km/h in the configurations with engine.     

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.     

Towards a model for electric vehicle noise emission in the European prediction method CNOSSOS-EU

The CNOSSOS-EU method is recommended in Europe for environmental noise prediction. In regards to road traffic, it includes vehicle noise emission models implicitly referring to internal combustion vehicles. The development of electrically driven vehicles calls for the future consideration of these vehicles in prediction models. On the basis of experimental data, the study reported in this paper proposes a noise emission model for extending CNOSSOS-EU to light electric vehicles. Correction terms to be applied to the propulsion noise component are determined. Investigations on a sample of tyres with good rolling resistance performance, which is a main tyre selection criterion on these vehicles, indicated that no correction is required for the rolling noise component. Differences between the noise emission from conventional vehicles and electric vehicles are discussed for several road surfaces. Owing to the limited vehicle sample as well as transitional statements, this new model for electric vehicles running at constant speed over 20 km/h should be considered as a first step towards the definition of this vehicle technology in CNOSSOS-EU.     

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.     

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.     

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.     

Dynamic noise modeling at roundabouts

Modeling spatial and temporal noise variations at roundabouts is a tedious task. Indeed, noise levels are strongly influenced by the complex vehicle interactions taking place at the entries. An accurate modeling of the merging process and its impact on vehicle kinematics, waiting time at the yield signs and queue length dynamics is therefore required. Analytical noise prediction models disregard those impacts since they are based on average flow demand patterns and pre-defined kinematic profiles. The only way to capture all traffic dynamics impacts on noise levels is to combine a traffic simulation tool with noise emission laws and a sound propagation model. Yet, such existing dynamic noise prediction packages fail in representing vehicle interactions when the roundabout is congested and are difficult to calibrate due to their numerous parameters. A new traffic simulation tool, specifically developed for roundabouts, is therefore proposed in this paper. It has few easy-to-calibrate parameters and can be readily combined with noise emission and propagation laws. The obtained noise package is able to produce relevant dynamic noise contour maps which can support noise emission assessment of local traffic management policies. Results are validated against empirical data collected on a French suburban roundabout on two different peak periods.     

Study of the road surface properties that control the acoustic performance of a rubberised asphalt mixture

Simultaneously with the fact that vehicle industry has been able to lower the noise emission from driving vehicles, tire/pavement noise has become the most significant source of traffic noise. In order to reduce it, low noise surfaces are seen as a practical solution. One of these types of surfaces may be elaborated with bituminous mixtures with crumb tire rubber added to the binder in high content by a wet process. However, the generation mechanisms involved in the tire/pavement sound and the reasons of the noise attenuation achieved with these mixtures are not so clear. This study analyses the different generation mechanisms that take place in the tire/pavement sound generation in these crumb tire rubber pavements. The surface properties of the in-service pavement, which are most important in controlling the acoustic performance (texture, acoustic absorption and dynamic stiffness or mechanical impedance), have been measured for the characterization of a test track constructed with and without crumb tire rubber. After results correlation of these surface characteristics in a pavement with crumb tire rubber added by a wet process, it seems that the parameters of roughness and texture could have a relevant role in the global tire/pavement sound emission, whereas dynamic stiffness influence is relatively minor.     

Procedure for determining manufacturing defects in a diesel engine in a workshop

Customers’ demands regarding the quality level of automobile vehicles are constantly increasing. These demands include noise, vibration and harshness (NVH) quality as an important item.The main source of NVH in the vehicle is the engine and this is particularly the case for diesel engines. The design effort to reduce the emissions of noise and vibration transmitted to the vehicle’s driver could be lessened because of the assembly process variation and assembly errors.In the present paper, a procedure for assessing these variations or errors is suggested in order to maintain NVH performances within the limits of the design and achieve the quality level expected by customers.In order to achieve it, the measurement of the engine vibration level through three sensors allocated at strategic points is suggested. Some objective criteria based on the vibration level at certain frequencies are established to determine possible assembly defects as a final step of the assembly process.     

Appraisal of Urban Road Traffic Noise in tier-II City (Surat City), India

Urban road traffic noise pollution has always been identified as a severe problem that affects urban populants. In developing nation, road traffic noise pollution depends on the composition of heterogeneous traffic composition. These traffic compositions contain vehicles, which have different sizes, speeds variations, a different dimension of vehicles. Environmental noise measurements have been carried out during day-time and night-time in different locations of tier-II city of India. The noise levels have been continuously measured over 24 h periods using kimo DB 300 class-2 noise level meter. The data contained in this research paper represent 768 measurement hours. All the information has been used to investigate the time patterns of the noise levels under a wide range of different conditions and to study the relationships between noise levels and traffic in urban areas. Maximum L_Aeq was observed 73.3 dB(A) at B₁₄ location and the minimum was recorded 65.7 dB(A) at C₃ location, which was greater than the central pollution control board (CPCB) prescribed limits during night time. A major reason for the generation of road traffic noise is due to the equal composition of 2-wheeler and 4-wheeler on the arterial road and heavy vehicles were recorded during morning peak and evening peak even though they are prohibited during peak hours.     

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.     

Study of the effectiveness of electric vehicle warning sounds depending on the urban environment

Electric and Hybrid Electric vehicles (EV and HEV) seem to be the future of transport in smart cities and the key for the total reduction of noise disturbance and pollution in urban areas. However, several problems have to be solved to guarantee the safety of these types of vehicle. Up to now, the use of HEV has shown the dangers of a “quiet” transport system in urban environments; in fact, it has been estimated that an HEV is twice as likely to be involved in a pedestrian crash as would be an internal combustion engine (ICE) vehicle in the same situation. With the aim of improving their safety, different kinds of warning sounds are being designed to increase the detectability of EV and HEV without themselves becoming new annoying sound sources. The sound directivity, frequency of emission and intensity of warning sound systems will guarantee their efficiency and limited noise impact.     

Two-parametric model of the spectrum of traffic noise in Tomsk

The technique of mapping urban noise is proposed on the basis of a two-parameter model of the acoustic noise spectrum. The acoustic noise and spatial distribution of the decay rate in Tomsk are mapped. The factors influencing the formation of the acoustic noise of traffic flow are described. Analysis is performed on how different operating modes of a vehicle??s internal combustion engine affect the background level of acoustic noise.     

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.     

Investigation of the dose-response relationship for road traffic noise in Assiut, Egypt

A field study has been carried out in urban Assiut city, Egypt. The goals of this study are: (1) to carry out measurements to evaluate road traffic noise levels, (2) to determine if these levels exceeds permissible levels, (3) to examine people’s attitudes towards road traffic noise, (4) to ascertain the relationship between road traffic noise levels and degree of annoyance. The measurements indicate that traffic noise noise levels are higher than those set by Egyptian noise standards and policy to protect public health and welfare in residential areas: equivalent continuous A - weighted sound pressure levels (L_A eq) = 80 dB and higher were recorded, while maximum permissible level is 65 dB. There is a strong relationship between road traffic noise levels and percentage of highly annoyed respondents. Higher road traffic noise levels mean that the percentage of respondents who feel highly annoyed is also increased.     

某汽车传动系扭振测试、诊断与数据处理分析

本文针对某轻型卡车由于传动系扭振导致加速过程中驾驶室内出现异常振动与轰鸣噪声现象进行研究。首先,为弄清车内振动噪声产生机理,对整车的扭振和车内振动噪声进行了实车道路试验;其次,对整车试验异常数据进行后处理,通过低通滤波和设置电压波动缓冲区的方法对其进行去噪和再生成,消除了加速工况下转速曲线失速和异常峰值的现象;最后,通过分析转速、振动和噪声数据得出：样车加速过程中发动机2阶激励频率达到整车传动系的固有频率时,引起了传动系扭转共振,连同传动轴的不平衡转动自振,通过悬置、中间支撑和后桥板簧传入到车内,引起驾驶室异常振动和轰鸣噪声。     

The contribution of heavy vehicles to urban traffic noise

The dominating influence of road traffic on the noise climate of the world's cities is now established and attempts to reduce the problem follow two main lines: The first involves ameliorating the effects of traffic stream noise; the second an attack on the noise levels of individual vehicles. The great expense involved in developing and building quieter vehicles justifies expending considerable effort in establishing the relative noise contribution of the vehicle types found in typical urban traffic mixtures. This paper describes the development of a field method for examining the effects of heavy vehicles such as trucks and buses on the noise profile of the traffic stream. The essential feature of the method involves synchronisation of a recorded voice commentary with the traffic noise. The graphical record of this noise can then be annotated to show what type of vehicles cause the peaks in the overall noise profile.     

基于改进声线跟踪法的室内交通噪声动态模拟

对碰撞点的有效性判断是传统声线跟踪法的一个重要步骤,在计算复杂的室内空间问题时计算量较大,为解决这一问题采用了一种与空间剖分相结合的改进的声线跟踪法。将该方法与微观交通流仿真和车辆噪声排放模型进行结合,实现了道路交通噪声透过窗户在多连通室内空间传播的动态模拟。最后采用该方法对相同道路和交通流条件下不同建筑朝向的4种布局室内噪声进行动态模拟。分析了室内交通噪声的大小和分布与建筑物布局、窗户的朝向、窗户的形式和面积等因数之间的关系。结果表明:窗户正对道路的房间比窗户侧对道路的房间噪声高4～6 d B(A),房间内等效声级与窗户面积的对数成正比关系。