Showing papers on "Noise barrier published in 2003"

Numerical Simulation of the Effect of Trees on Downwind Noise Barrier Performance

Abstract: Summary Simulating sound propagation outdoors in time-domain taking into account the effect of wind by means of steadystate Computational Fluid Dynamics (CFD) has recently shown to be very useful. In this paper, the important effect of wind on noise barrier performance and the effect of rows of trees to improve wind profiles around noise barriers are modelled. A finite-difference time-domain simulation model is adapted for sound propagation outdoors in a complex, non-uniform background flow. The simulation of a typical traffic noise situation, where at either side of a line source a noise barrier is present, needs appropriate, non-reflecting boundary conditions like Perfectly Matched Layers (PML) to limit the simulation domain. The PML method is extended for sound propagation in background flow. The numerical model is validated based on two wind tunnel experiments at scale. These show that the model can be used successfully to simulate both the screen-induced refraction of sound and the effect of windscreens to improve downwind noise barrier performance. The influence of parameters involved like the porosity of the canopy of the trees, wind speed and distance between source and noise barrier were studied. Global effects of different configurations of windscreen for typical traffic noise are evaluated in an area of interest behind the downwind noise barrier, exceeding the study region in the wind tunnel experiments.

A review of research on environmental noise barriers

Abstract: During the past four decades, extensive research has been carried out on different noise barrier shapes using analytical and physical modelling as well as full scale testing. This paper reviews traffic noise barrier research and its findings to date. It provides a catalogue of noise barrier profiles; identifying the relative acoustic benefits of each and the physical principles on which they operate. The likely effects of ground and atmospheric conditions on their absolute acoustic performance are described. The types of barriers which are commonly used in practice and those deserving further attention are highlighted. Based on the findings of previous work, recommendations are made on possible areas of further research.

Geographical information system for traffic noise analysis and forecasting with the appearance of barriers

Abstract: This paper describes a road traffic noise calculation and visualization package TNoiseGIS. It is implemented by utilizing the inbuilt database and spatial routines of a popular commercial Geographical Information System (GIS). The noise calculations can be made according to either of two alternative noise calculation models: the UK CORTN and US FHWA models. These models are applicable for calculating noise levels along highways with free flowing traffic. By applying the inbuilt spatial operations to the geographically located information, noise emission values can automatically be provided for any number of receptor points using either algorithm. The graphical user interface of the GIS simplifies the input of the attributes of the different receptor points and road links. Line and block barriers can be defined and applied with the interpolation technique for calculating traffic noise on receiver points along the back edge of barrier parallel to roadway. As a result, all noise levels behind the barrier can be efficiently estimated. In addition to the calculation of noise emission values for a specified set of receptor points, the variation in the noise levels along the highway can be visualized in the form of noise contours. Such contours provide a visual description of the soundscape and also information on the importance of different factors for soundscape quality. By changing traffic flow parameters such as the localization of planned roads, dwellings, and barriers with different size and location, TNoiseGIS functions as a road traffic noise prediction tool and a tool for planning environmentally friendly road and road traffic noise solutions. The noise calculations and visualization algorithms are implemented by means of scripts that will be made available at a lower cost and also user modifiable.

Assessment of the photovoltaic potential on noise barriers along national roads in Italy

Abstract: Implementation of photovoltaic noise barriers is an interesting application for large scale PV installations with cost sharing and no land consumption. In this work, a GIS based analysis of the theoretical potential to be installed on noise barriers along Italian national roads has been carried out. Estimation of the road extent to be equipped with PV sound barriers has been obtained by provisional algorithms, on the basis of traffic flow, global radiation, meteorological conditions, geometrical and morphological configuration of the surroundings. The results reveal the presence of many suburban road sections acoustically affecting built-up areas with a favourable exposition to solar radiation and the existence of a large market where photovoltaics can be efficiently integrated into acoustical mitigation interventions.

Noise prevention wall system comprising a base and a transparent top part

Abstract: A noise barrier system composed of a base and a transparent superstructure. A support holds at least two adjacent transparent noise barrier elements and includes a point-fastening of the transparent noise barrier element. A position of upper holding points of the transparent superstructure is arranged at a height of from 70 to 90% of a total height of the transparent noise barrier element and at a distance of from 3 to 50 times a thickness of the transparent noise barrier element from a vertical edge. An upper side of the transparent noise barrier element has a flexure, an angle of the flexure being from 30° to 90° from vertical, and a width of an angled region being from 5 cm to 50 cm, and an entire length of a lower side of the sheet is secured within a groove-shaped depression.

Florida Noise barrier evaluation and computer model validation

Abstract: The results of a project that investigated the effectiveness of in situ noise barriers in Florida are presented. The prediction accuracy of the FHWA Traffic Noise Model (TNM) is compared with STAMI...

Porous elastic road surface as an ultimate highway noise measure

Abstract: This paper describes how highway traffic noise in urban areas of Japan is a serious problem, not only for residents along highways, but also for highway administrators. Only 13 percent of urban highways have met the environment standard for noise. Noise barriers cannot be used as a noise countermeasure on the majority of highways on which access is not controlled. Noise levels of areas along some urban highways exceed the standard by 15 dB(A) or more. This problem is impeding new highway construction in urban areas. Porous asphalt pavement has recently been introduced on urban highways in Japan. Its noise reduction effect of 3 dB(A) is insufficient, because it only improves the noise environment satisfaction rate by a few percent. Furthermore, the durability of its noise reduction effect usually seems to be only three years, which is shorter than its life-cycle as pavement. The Public Works Research Institute (PWRI) has, since 1993, been developing a new low-noise pavement named "Porous Elastic Road Surface" (PERS). This new pavement has a porous structure composed of granulate rubber made from old used tires as its aggregate and urethane resin as its binder. Its porosity is approximately 40 percent. The pavement was first proposed in Sweden in the 1970's, however, Swedish researchers have failed to improve it as a practical pavement. Noise reduction levels are 15 dB(A) for cars and 8 dB(A) for trucks. The author estimates that the potential noise reduction levels in Leq exceed 10 dB(A). More than 90 percent of highways in urban areas would meet the standard if this noise reduction level were achieved. The PWRI has already solved several of the problems with PERS, for example, insufficient adhesion between the pavement and the base course, low skid resistance, and its poor fireproof performance. Its technical level has already reached the stage of test construction on urban highways. This paper examines the general performance of PERS obtained through past development at the PWRI. It also summarizes the results of recent research done to further improve the noise reduction levels of PERS and the first test construction using PERS in Japan. The final noise reduction target for any type of vehicle is between 15-20 dB(A). The author expects that PERS will reduce highway traffic noise problems in urban areas of Japan to a minor, negligible level in the near future.

Absorptive sound barriers: effects of three potential changes to current design standards of virginia department of transportation

Abstract: The Virginia Department of Transportation (VDOT) currently designs absorptive sound barriers with their entire face absorptive [noise reduction coefficient (NRC) of 0.8 or greater]. Using the Federal Highway Administration Traffic Noise Model, the sound level increases caused by three modifications to current VDOT practice were investigated: a more reflective barrier surface (NRC = 0.7), a 6-in. (15-cm) reflective cap, and a 2-ft (61-cm) reflective base. These increases were computed for receivers up to 40 ft (12.2 m) above the ground and 1,000 ft (305 m) behind the barrier. The computations included three barrier locations--barrier opposite receivers, barrier same side as receivers, and barriers on both sides--at several barrier heights and distances from the roadway. They also included two roadway widths and two traffic conditions, to span the extreme ranges of these variables. Results indicate that for a barrier opposite the receivers, the more reflective surface caused a maximum increase of 1.3 dB, the 2-ft (61-cm) reflective base caused a maximum increase of 1.7 dB, and all three modifications combined inflated this increase to 2.7 dB. For a barrier on the same side of the roadway as the receivers, no situations caused increases greater than 1 dB. Finally, for barriers on both sides of the roadway, the more reflective surface caused a maximum increase of 1.1 dB, and all three modifications combined inflated this increase to 1.5 dB. A table of resulting sound level increases for the full field of computed receivers--for the worst-case situations encountered in the computations--is included.

Traffic noise attenuation by scattering, resonance and dispersion

Abstract: The purpose of this investigation is to analyze various techniques of sound attenuation which can be used to minimize traffic noise from heavy traffic circulation in urban areas, and to improve sound quality in these areas using selective absorption in specific frequency ranges, plus to reduce the degree of annoyance of traffic noise. This study covers uncontrollable noise sources such as trucks, automobiles and trains, in heavy traffic urban areas. Different methods of noise energy reduction are discussed, including sound attenuation by selective absorption, scattering and cavity resonance in the sound barriers. Multiple scattering on sound absorbing road and barriers are considered to increase noise energy dissipation in unwanted frequency ranges. The effects of dispersion and change in the frequency content of the noise with distance are studied. An elimination of the most disturbing frequency components of these uncontrollable noise sources improves sound quality from these sources and increases our overall capabilities in controlling noise pollution in the urban environment.

Living with noise

Abstract: According to the most recent data available from 1987, noise from highway traffic affects more than 18 million people in the U.S. As highway systems continue expanding, increased traffic volumes will result in higher levels of traffic noise for residents of adjacent neighborhoods. This article describes how, through advanced planning and shared responsibility, local governments and developers working cooperatively with Federal and State governments can plan, design, and construct new development projects and roadways that minimize the adverse effects of noise from highway traffic. The use of noise-compatible land use planning encourages the location of less noise-sensitive land uses near highways, promotes the use of open space separating roads from developments, and suggests special construction techniques that lessen the impacts of highway traffic noise.

N480) the use of mls based methods for characterising the effectiveness of noise barriers and absorptive road surfaces

Abstract: Maximum Length Sequence (MLS) methods are currently being specified for a wide range of applications including test methods for characterising the performance of noise barriers. The relative ease of measurement, including the absence of calibration and high noise immunity, make the method particularly attractive for in-situ measurements. The paper reviews TRL experience in exploring and using the method for characterising sound absorption and sound transmission of a range of noise barriers and road surfaces. The experimental investigations were carried out for the Transport Research Foundation. For the measurement of sound absorption some difficulties have been experienced with reflective samples. It is concluded that the method is likely to prove inaccurate for samples with low sound absorption. The measurement errors involved in characterising sound transmission are relatively small; however, anomalous results can result where discrete air gaps occur. (A)

Excess attenuation of road traffic noise by detached houses : Predictions when receiving points are lower than houses

Abstract: The purpose of this paper is to present a simple method for predicting the excess attenuation of road traffic noise by detached houses. The Acoustical Society of Japan (ASJ) presents one method; however, it cannot estimate noise levels at specific individual points in residential areas. In this paper, therefore, an experiment is performed with a one-twentieth scale model and a new empirical formula for excess attenuation, based on only five parameters, is proposed. The validity of the formula is verified through additional experiments, a comparison with the current method, and noise measurements in actual residential areas. This new and simple method is applicable to evaluations of environmental quality standards for noise.

Comprehensive review of collected noise information at barrier sites

Abstract: This report describes the results of a detailed analysis of in-situ measurements for 19 noise barriers in the State of Florida. This report is a continuation of work presented in two previous Florida Department of Transportation (FDOT) reports, which are described in the introduction. This report investigates, in greater detail, the substantial database produced by this project. This investigation evaluated spectral differences of predicted and measured ground effects and high frequency deviations between federal prediction methods compared to measured data. This work also produced custom software that provided a visualization of the formation of shadow zones behind existing barriers. In addition, new empirical methods were developed to estimate the length of shadow zones behind highway noise barriers. This software can lead to more effective design of future highway noise barriers.

Florida Noise Barrier Evaluation and Computer Model Validation 03-3296

Abstract: This paper describes a project investigating the effectiveness of in-situ noise barriers in the state of Florida and compares the prediction accuracy of the FHWA Traffic Noise Model (FHWA TNM) to STAMINA 2.0 and 2.1 (Florida specific). A total of twenty barrier sites were visited over a three year period that resulted in 844 discrete, 20 minute Leq measurements behind the barriers. Barrier insertion loss was determined using the ANSI indirect barrier method. Work was also conducted to develop a methodology for estimation of shadow zone length created behind highway noise barriers. Most of the barriers tested are effective (>5 dB:LAeq insertion loss at distances equivalent to the first row of homes) with the exception of one site due to marginal additional shielding from a berm/barrier combination. At distances representative of the second row of homes, only three sites had less than a 5 dB insertion loss. Overall, measurements indicate that the barriers are providing substantial reduction for the neighbors along the highway. In terms of error statistics, TNM proved to be the best prediction model when considering all test sites, however the STAMINA models were more accurate at source level prediction. TNM, using the “Average” pavement input, over-predicted the reference sound levels measured at these sites. TNM predicted levels using the “OGAC” (open graded asphalt concrete) input were improved (under 2 dB:LAeq of error) over those using the “Average” pavement type input. This is expected since Florida uses an open graded, asphalt friction mix.

Performance of Noise Barriers with Absorptive Edge Treatments

Abstract: The installation of sound-absorptive materials near the edge of a noise barrier is known to increase its insertion loss. First, scale-model experiments were performed to compare the performance of ...

Noise barrier system composed of a base with a transparent superstructure

Abstract: A noise barrier system composed of a base and a transparent superstructure. A support holds at least two adjacent transparent noise barrier elements and includes a point-fastening of the transparent noise barrier element. A position of upper holding points of the transparent superstructure is arranged at a height of from 70 to 90% of a total height of the transparent noise barrier element and at a distance of from 3 to 50 times a thickness of the transparent noise barrier element from a vertical edge. An upper side of the transparent noise barrier element has a flexure, an angle of the flexure being from 30° to 90° from vertical, and a width of an angled region being from 5 cm to 50 cm, and an entire length of a lower side of the sheet is secured within a groove-shaped depression.

An Application of a New Roadside Barrier to Traffic Noise Mitigation

Abstract: In this paper, the noise reduction performance of a new roadside barrier, which is called double screen barrier, is presented and studied theoretically and experimentally. The theoretical predictions are developed and based on Macdonald's diffraction theory. A case study of traffic noise mitigation is presented to show the effectiveness of the different barriers, including vertical barrier, cantilever barrier, double screen barrier, and partial enclosure. It has been found that the double screen barrier gives the best noise reduction performance among the four mitigation measures. A 1: 4 scale model of the proposed double screen barrier has been developed. The experimental results have good agreements with the predictions, provided that absorption material must be fully filled into the trough of the V-shape panel of the double screen barrier to reduce the sound reflection, and the gap width between the V-shape panel edges must be large when compared with the wavelengths of frequencies of interest.