Showing papers on "Noise barrier published in 1997"

Noise reduction by a barrier having a random edge profile

Abstract: Sound generally reaches the shadow zone behind a noise barrier by diffraction, or scattering, from the edge at the top of the barrier. By redirecting the incident sound into the shadow zone, the edge acts as a line source. For the traditional straight-edge barrier, the line source is coherent. Since a crooked line source is less coherent, we propose to improve barrier performance by making the edge randomly jagged. Laboratory model experiments to compare insertion loss of straight- and jagged-edge barriers are reported here. A spark was used as a point source, the barriers were thin (compared to a wavelength), and ground and meteorological effects were not important. After preliminary measurements showed that a jagged edge can produce significantly more insertion loss at high frequency, a three level full factorial experiment was done. The results led to an empirical equation for insertion loss of a jagged-edge barrier. Improvement over the straight barrier was found to increase with jaggedness. An unexplained result was the poorer performance of the jagged-edge barrier at low frequency.

Effects of high-sided vehicles on the performance of noise barriers

Abstract: The attenuation produced by a given barrier can be maximized by placing it as close to the noise source or receiver as possible. This fact and the availability of land often means that barriers are situated close to the edge of the road. In this position the performance of the barrier can be degraded by the effects of multiple reflections of sound between the sides of the vehicles and the barrier. This paper reports the results of calculations, carried out using a two-dimensional boundary element model, of the attenuation produced by various configurations of barrier adjacent to a traffic stream. Spectra of insertion loss and the mean broadband insertion loss in the shadow region are considered. The effects of the height of the vehicle, the distribution of absorbing material on the traffic-facing side of the barrier, and the slope of this face are considered quantitatively in terms of the peak noise level. It is concluded that serious degradation of the performance of the barrier can occur for some situat...

Effectiveness of noise barriers on an interstate highway: a subjective and objective evaluation

Abstract: The objective of this study was to determine the actual and perceived effectiveness of noise barriers along interstate highways. Using a 5-mile section of Interstate 71 in the greater Cincinnati area as the study area, traffic noise readings and opinions of residents living along the sections of the highway were recorded. Noise readings were taken before and after the noise barriers were erected. A questionnaire was designed to elicit noise-related annoyance of the residents in the areas adjoining the highway. The results indicated that, in general, noise barriers were effective as indicated by a reduction in noise levels by as much as 11 dBA. The barriers, however, failed to bring noise levels for locations closer to the highway within the levels desired by the government (67 dBA). Most residents living right next to the highway were very satisfied with the installation of noise barriers. In general, these individuals felt that the quality of life improved with the noise barrier installation. The same, however, was not true of residents living a few blocks away from the highway--they felt the noise barriers were a waste of money. There was no significant difference in traffic noise pattern during the weekdays or weekends. Noise readings taken in two different locations were observed to be similar.

Perception of Traffic Noise Barrier Effectiveness: Public Opinion Survey of Residents Living near I-71

Abstract: The completion of the largest Ohio Department of Transportation traffic noise abatement project in 1995 was met with public controversy over the effectiveness of the noise barriers. A public opinion survey was designed to obtain the perceptions of the residents in the project area. In a departure from most surveys of traffic noise barrier effectiveness, the coverage was not limited to the first or second row of houses, but was extended to 800 m on each side of the roadway. It was found that the larger survey area was needed to avoid misleading conclusions. Overall perceptions of noise barrier effectiveness were found to vary with distance from the roadway and with noise barrier configuration.

Good fences make good neighbors : Highway noise barriers and the built environment

Abstract: Noise barriers have become a prominent feature on today's landscape Unfortunately, they have also become a feature associated with insensitivity toward the built environment Designers could avoid the negative visual impact that noise barriers frequently create by increasing their awareness of aesthetics in the design process In an effort to improve the quality of noise barrier design, the New Jersey Department of Transportation's, Bureau of Environmental Analysis (BEA) altered the design process for its I-76/I-295 Type II noise abatement study The first objective of the study was to acoustically engineer a barrier that would abate the noise for residents along the affected roadway corridor The second was to develop an architectural design that would be aesthetically pleasing to the corridor resident and the roadway users Typically, architects were brought into the design process at the end to review the aesthetic impact of the wall and add architectural features On the I-76/I-295 project, BEA initi

Traffic noise measurements at fm 3009 greenfield village subdivision, city of schertz, texas

Abstract: Objectives of the studies were to: (1) determine by quantitative measurements and computer simulation modeling the effectiveness of the noise barriers; (2) determine the traffic noise intrusion through openings in the barriers at streets entering the residential areas; (3) conduct a community opinion survey to characterize the subjective effectiveness of the noise barriers; and (4) compare field measurements with computer-modeled results. Project efforts resulted in the development and application of a source-referenced noise level measurement and spatial contouring method for characterizing noise intrusion through the barrier openings. Similar measurements were used in comparing noise barrier insertion loss measurements with measurements at locations without the noise barrier. A mail-distributed opinion survey questionnaire was developed that resulted in a 60% return from the 289 residences in the subdivision. The overall results of the opinion survey indicated that 69% of the primary receiver residences had positive opinions concerning the effectiveness of the noise barrier installation. Field measurements indicated the insertion loss along the continuous noise barrier to be 8-12 dB in the yards of the primary receivers adjacent to FM 3009. Noise intrusion through residential street openings in the barrier panels reduced the insertion loss measured in the yards of the primary receiver by 4-6 dB, depending on the specific primary receiver yard layout.

Preliminary assessment of traffic noise barrier effectiveness for project ham-71-11.44

Abstract: The completion of the traffic noise barrier project HAM-71-11.44 in Ohio was met with strong reaction from those living in the project area. Many residents complained that noise levels had actually increased at their location as a result of the project, while others claimed that levels had decreased where they lived. The preliminary assessment project was initiated to determine the nature and extent of any problems that had occurred with the construction of the noise barriers. A two-pronged approach was used for the study. First, a survey of residents was conducted to characterize the residents' perception of changes in noise levels due to construction of the barriers. Second, a physical investigation of the project area was made, which included roadway and barrier geometries, traffic characteristics before and after barrier construction, and acoustical measurements to characterize the noise environment in the project area. From the survey, it was found that residents living in the range of 180 m from the highway were more likely to perceive an increase in noise levels or to view the barriers as ineffective compared to those living less than 180 m or greater than 540 m from the highway. Further, those residents protected by parallel barrier configurations were more likely to perceive increased levels than those protected by single barriers. As a result of the physical investigation, changes in the characteristics of the traffic noise source itself were eliminated as a cause for the perceived increase in noise levels since the construction of the noise barriers. From noise level measurements, it was found that most residents living in the first row of houses nearest the noise barriers have experienced a substantial noise reduction due to the construction of the noise barriers. However, noise barrier effectiveness has been compromised in several locations due to barrier overlap gaps located at the transition between roadway cut and fill sections. To address the issue of perceived noise level increases, a number of mechanisms were identified for further study, including multiple reflections between parallel noise barriers and changes in ground attenuation due to barrier construction.

Mounting structure of solar cell panel of solar-ray energy utilizing power generation utilizing noise barrier for road

Abstract: PROBLEM TO BE SOLVED: To use solar-ray energy effectively as much as possible by making the height of the webs of fittings for solar-cell panels installed on the southern surface side of a noise barrier differ and adjusting setting angles. SOLUTION: Solar-cell panels 3... are mounted on the southern surface side of a noise barrier set up along a road passed east and west, and power generation utilizing solar-ray energy is conducted. The solar-cell panels 3 are fitted at specified places on the southern surface side of the noise barrier in arrangement in long size in the longitudinal direction of the road by using Z-shaped steel-like fittings under the state, in which the panels 3 are projected forward, at slight intervals from the surfaces of sound-insulating panels 2A.... The solar- cell panels 3 are adjusted at setting angles, where solar-ray energy can be used effectively as much as possible in response to the moving locus of the sun, by making the height of the webs of the fittings differ.

Noise control earth berms : guidelines for the use of earth berms to control highway noise

Abstract: Since 1989, the Ministry of Transportation & Highways of British Columbia (MoTH) has had a noise impact mitigation policy which applies to all new or upgraded freeway and expressway projects. This policy is intended to prevent excessive noise impacts at residences and educational facilities and requires that mitigation measures be considered wherever project-related noise increases are predicted to exceed certain limits. Where such mitigation measures are warranted, cost-effective and widely supported by the directly affected community, they are to be carried out. Mitigation measures generally take the form of noise barriers constructed within MoTH right-of-way. Three basic configurations are employed: walls, earth berms or berm/wall combinations. The MoTH policy limits the height of walls to 3 m, but no such limit exists for earth berms or berm/walls. Given their natural appearance and potentially lower costs, earth berms have often been the preferred form of mitigation where space is available. Since the MoTH noise policy requires that mitigation measures achieve average noise reductions of 5 dBA or more, it is crucial that the relative noise reduction capabilities of the three forms of noise barriers be well understood. While experimental assessments to date have yielded mixed results, some highway noise prediction models assign a noise reduction bonus of 3 dBA to earth berms in recognition of their relatively broad and soft tops. To assess the validity of this "soft top correction" and to explore the effects of adding walls to the tops of earth berms, MoTH has funded research by the U.B.C. Mechanical Engineering Department (through the Professional Partnership Program) and Wakefield Accoustics Ltd. (A)

A review of parallel traffic noise barrier literature

Abstract: It is widely accepted that a single noise barrier beside a highway will provide a degree of noise reduction for neighboring homes. An interesting issue arises when residential areas line both sides of the highway, requiring two parallel barriers, one on each side of the highway. An abundance of research has been carried out to examine this situation. The research suggests that this configuration allows for multiple reflections to occur between the two barriers, unfortunately resulting in less noise reduction for both residential areas. Researchers attacking this problem have uncovered many relevant issues. This paper will summarize these issues and will class them into those in which there is consensus and those in which there is no consensus. Researchers agree that multiple reflections exist in a parallel wall situation, that these reflections cause an insertion loss degradation, that the insertion loss degradation can be controlled, and that making barriers absorptive or tilting them is effective in reducing the degradation. They do not agree on the extent of insertion loss degradation, the significance of environmental variables such as ground cover, or the limits to improvements from absorptive or tilting barriers.

Analysis of noise abatement due to absorptive device at the top of highway noise barriers by boundary element method

Abstract: 道路遮音壁先端に設置して騒音低減効果を高める音響装置 (ノイズリデューサー) について, その設置効果の解析を波動音響に基づく理論計算によって行った. 理論計算は二次元境界要素法を用いて行い, その設置効果の特徴を明らかにするとともに, 現地実測による測定値ともよい一致が得られることを示した.