Jérôme Defrance

NMPB-Routes-2008: The Revision of the French Method for Road Traffic Noise Prediction

The revision of the French method for road traffic noise prediction (NMPB-Routes-2008) is now published. The major principles of NMPB-Routes-2008 are outlined. The most important modifications regarding the source are the reduction of its height and the introduction of two different spectra. In this complete revision, the main change is the replacement of the ISO 9613-2-based ground attenuation formula in downward-refraction conditions by the formula for ground attenuation in homogeneous conditions of NMPB-Routes-1996 with corrected heights in order to take into account the mean curvature of rays (refraction) and its scattering (turbulence). NMPB-Routes-2008 adds an attenuation term for an occasional cutting embankment. Regarding diffraction the dif formula is now more suitable for low height barriers. The validation of NMPB-Routes-2008 with respect to experiment is presented. It is based on measurement campaigns on 6 sites with complex geometries and shows that the predicted noise levels obtained from NMPB-Routes-2008 are significantly closer to experimental results than in the case of the original method. S. Hirzel Verlag.

Indoor noise exposure at home: a field study in the family of urban schoolchildren.

This article aims at evaluating indoor noise levels at home and investigating the factors that may influence their variability. An 8-day noise measurement campaign was conducted in the homes of 44 schoolchildren attending the public primary schools of Besançon (France). The presence of the inhabitants in the dwelling and the noisy events occurring indoors and outdoors was daily collected using a time-location-activity diary (TLAD); 902 time periods were analyzed. The indoor noise level increased significantly with the outdoor noise level, along with the duration of the presence or level of activity of the inhabitants at home. However, this effect may vary according to the period of day and the day of the week. Moreover, a significant part of the day and evening indoor noise level variability was explained when considering the TLAD variables: 46% and 45% in the bedroom, 54% and 39% in the main room, respectively. Our results highlight the complexity of the indoor environment in the dwellings of children living in an urban area. Combining the inhabitant presence and indoor noise source descriptors with outdoor noise levels and other dwelling or inhabitant characteristics could improve large-scale epidemiological studies. However, additional efforts are still needed, particularly during the night period.

Calculations of low height noise barriers efficiency by using Boundary Element Method and optimisation algorithms

Nowadays, roads and railways are often quoted as the most annoying source of noise for the living environment. This problem of ground transportation noise is present in extra‐urban environments as well as in town centres. Traditional noise barriers are in many cases not suited for acoustic protection in urban areas mainly because of their height. Previous studies have shown a significant efficiency of low height noise protections (kind of urban furniture) for the decreasing of noise levels in semi‐opened areas such as city parks, places, and large avenues. However, the simulations of low height noise protections requires specific numerical codes since ray tracing methods are not suited for barriers lower than around 2 m. This paper proposes a way to implement an approach with allow to simulate low height noise protections in engineering calculation methods. This can be done by creating a database using a Boundary Element Method numerical code combined with optimisation algorithms. Work is still in progres...

The revision of the French method for road traffic noise prediction

A revision of the French method for road traffic noise prediction (NMPB‐Routes‐2008) has been released. The major principles of NMPB‐Routes‐2008 are outlined. The most important modifications regarding the source are the reduction of its height and the introduction of two different spectra. In this complete revision, the main change is the replacement of the ISO 9613‐2 ‐ based ground attenuation formula in downward conditions by the formula for ground attenuation in homogeneous conditions of NMPB‐Routes‐1996 with corrected heights in order to take into account the mean curvature of rays (refraction) and its spreading (turbulence). The revised NMPB adds an attenuation term for an occasional cutting embankment. Regarding diffraction the Δdif formula is now suitable for low height barriers. The validation of the revised NMPB with respect to experiment is presented. It is based on measurement campaigns on 6 sites with complex geometries and shows that the predicted noise levels obtained from the revised NMPB ...

Computational model for long-range non-linear propagation over urban cities

A computational model for long-range non-linear sound propagation over urban environments is described. First the probability model of the geometrical parameters of an urban environment are determined using Information Theory and the Maximum Entropy Principle. The propagation model is then presented: it is based on the non-linear parabolic equation (NPE) and its extension to propagation in porous media, in which the urban layer of the real system is represented by a porous ground layer. The uncertainties introduced by the use of this simplified model and the presence of the variability of the real system are taken into account with a probabilistic model. Reference solutions are obtained thanks to the boundary element method (BEM); these experimental observations are then used to identify the parameters of the probability model. This inverse stochastic problem is solved using an evolutionary algorithm which involves both the mean-square method and the maximum likelihood method. Applications and model validation are then presented for two different urban environment morphologies. It is shown that the identification method provides an accurate and robust way for identifying the stochastic model parameters, independently of the variability of the real system. Constructed confidence regions are in good agreement with the numerical observations.

Nonlinear parabolic equation model for finite-amplitude sound propagation over porous ground layers

The nonlinear parabolic equation (NPE) is a time-domain method widely used in underwater sound propagation applications. It allows simulation of weakly nonlinear sound propagation within an inhomogeneous medium. So that this method can be used for outdoor sound propagation applications it must account for the effects of an absorbing ground surface. The NPE being formulated in the time domain, complex impedances cannot be used and, hence, the ground layer is included in the computational system with the help of a second NPE based on the Zwikker-Kosten model. A two-way coupling between these two layers (air and ground) is required for the whole system to behave correctly. Coupling equations are derived from linearized Eulers equations. In the frame of a parabolic model, this two-way coupling only involves spatial derivatives, making its numerical implementation straightforward. Several propagation examples, both linear or nonlinear, are then presented. The method is shown to give satisfactory results for a wide range of ground characteristics. Finally, the problem of including Forchheimers nonlinearities in the two-way coupling is addressed and an approximate solution is proposed.

Innovative tools for urban soundscape quality: Real-time road traffic auralization and low height noise barriers

Although noise exposure has been unanimously recognized for its impacts on people’s health, noise is still a current problem in many cities across the world. Besides, most noise analysis tools are based on long term average levels, which were initially meant to be used for inter-city infrastructures and are therefore insufficient to quantify the soundscape quality in urban environments. In this paper, we present some of the recent developments and results regarding two classes of innovative tools dedicated to the improvement of urban soundscape quality. First, recent advances in the field of real-time auralization of road traffic noise are presented and the benefit of realistic sound field restitution as a new analysis tool for the evaluation of urban planning projects is discussed and demonstrated. Second, some promising results regarding innovative urban noise reducing devices, taken among other works from the European project HOSANNA, are presented. In particular, the potential of vegetation and low he...

Multiple pregnancies and air pollution in moderately polluted cities: Is there an association between air pollution and fetal growth?

BACKGROUND Multiple pregnancies (where more than one fetus develops simultaneously in the womb) are systematically excluded from studies of the impact of air pollution on pregnancy outcomes. This study aims to analyze, in a population of multiple pregnancies, the relationship between fetal growth restriction (FGR), small for gestational age (SGA) and exposure to air pollution in moderately polluted cities. METHODS All women with multiple pregnancies living in the city of Besançon or in the urban area of Dijon and who delivered at a university hospital between 2005 and 2009 were included. FGR and SGA were obtained from medical records. Outdoor residential nitrogen dioxide (NO2) exposure was assessed using the mothers address, considering a 50 m radius buffer over the following defined pregnancy periods: each trimester, entire pregnancy and two months before delivery. Logistic regression analyses were performed. RESULTS This study included 249 multiple pregnancies with 506 newborns. The median of NO2 concentration considering a 50 m radius buffer during entire pregnancy was 23.1 μg/m3 (minimum at 10.1 μg/m3 and maximum at 46.7 μg/m3). No association was observed between NO2 and SGA whatever the pregnancy period (the odds ratio (OR) range 0.78 to 0.88). Regarding FGR, the OR associated with an increase of 10 μg/m3 of NO2 exposure during entire pregnancy was 1.52 (95% Confidence Interval (CI): 1.02-2.26). Similar results were observed for NO2 exposure during the various pregnancy periods. CONCLUSIONS These results are in line with an association between NO2 and fetal growth in multiple pregnancies for an exposure mostly below the threshold set out in European legislation.

Advances regarding a new method for measuring the in situ noise abatement performance of urban noise reducing devices

Recent works regarding urban noise reducing devices have clearly shown the interest of such solutions in order to improve the sound quality in urban areas. To accompany the development of new products, it now becomes necessary to provide a technical regulatory framework for all stakeholders (manufacturers, city planners, consulting acoustical engineers, etc.) in order to guarantee quality, efficiency, and compliance with urban implementation requirements. This is the main purpose of the technical group CNEA-U, affiliated to the French commission for standardization of road traffic noise reducing devices. As part the technical group activities, a new method for measuring the in situ noise abatement performance of urban devices adapted to the urban context has been developed. The purpose of the method is to provide an indicator of the noise reduction effect of a particular product, measurable in situ but depending as little as possible on environmental effects. To reach this purpose, the parameters of the m...

Does low to moderate environmental exposure to noise and air pollution influence preterm delivery in medium-sized cities?

Background Preterm birth (PB) is an important predictor of childhood morbidity and educational performance. Beyond the known risk factors, environmental factors, such as air pollution and noise, have been implicated in PB. In urban areas, these pollutants coexist. Very few studies have examined the effects of multi-exposure on the pregnancy duration. The objective of this study was to analyse the relationship between PB and environmental chronic multi-exposure to noise and air pollution in medium-sized cities. Methods A case-control study was conducted among women living in the city of Besançon (121 671 inhabitants) or in the urban unit of Dijon (243 936 inhabitants) and who delivered in a university hospital between 2005 and 2009. Only singleton pregnancies without associated pathologies were considered. Four controls were matched to each case in terms of the mothers age and delivery location. Residential noise and nitrogen dioxide (NO2) exposures were calculated at the mothers address. Conditional logistic regression models were applied, and sensitivity analyses were performed. Results This study included 302 cases and 1204 controls. The correlation between noise and NO2 indices ranged from 0.41 to 0.59. No significant differences were found in pollutant exposure levels between cases and controls. The adjusted odds ratios ranged between 0.96 and 1.08. Sensitivity analysis conducted using different temporal and spatial exposure windows demonstrated the same results. Conclusions The results are in favour of a lack of connection between preterm delivery and multi-exposure to noise and air pollution in medium-sized cities for pregnant women without underlying disease.