Noise barrier

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The sound tube in Melbourne, Australia, designed to reduce roadway noise without detracting from the area's aesthetics. TullamarineFwy.jpg
The sound tube in Melbourne, Australia, designed to reduce roadway noise without detracting from the area's aesthetics.

A noise barrier (also called a soundwall, noise wall, sound berm, sound barrier, or acoustical barrier) is an exterior structure designed to protect inhabitants of sensitive land use areas from noise pollution. Noise barriers are the most effective method of mitigating roadway, railway, and industrial noise sources – other than cessation of the source activity or use of source controls.

Contents

In the UK and Europe, noise barriers installed next to roads must be UKCA or CE marked as a complete system in accordance with BS EN 14388:2005 relating to road traffic noise reducing devices. [1]

In the case of surface transportation noise, other methods of reducing the source noise intensity include encouraging the use of hybrid and electric vehicles, improving automobile aerodynamics and tire design, and choosing low-noise paving material. Extensive use of noise barriers began in the United States after noise regulations were introduced in the early 1970s.

History

Noise barriers have been built in the United States since the mid-twentieth century, when vehicular traffic burgeoned. I-680 in Milpitas, California was the first noise barrier. [2] In the late 1960s, analytic acoustical technology emerged to mathematically evaluate the efficacy of a noise barrier design adjacent to a specific roadway. By the 1990s, noise barriers that included use of transparent materials were being designed in Denmark and other western European countries. [3]

Acoustical scientist measures sound in noise barrier design study, Santa Clara County, California. Noisebarrierm.jpg
Acoustical scientist measures sound in noise barrier design study, Santa Clara County, California.

The best of these early computer models considered the effects of roadway geometry, topography, vehicle volumes, vehicle speeds, truck mix, road surface type, and micro-meteorology. Several U.S. research groups developed variations of the computer modeling techniques: Caltrans Headquarters in Sacramento, California; the ESL Inc. group in Sunnyvale, California; the Bolt, Beranek and Newman [4] group in Cambridge, Massachusetts, and a research team at the University of Florida. Possibly the earliest published work that scientifically designed a specific noise barrier was the study for the Foothill Expressway in Los Altos, California. [5]

Numerous case studies across the U.S. soon addressed dozens of different existing and planned highways. Most were commissioned by state highway departments and conducted by one of the four research groups mentioned above. The U.S. National Environmental Policy Act, enacted in 1970, effectively mandated the quantitative analysis of noise pollution from every Federal-Aid Highway Act Project in the country, propelling noise barrier model development and application. With passage of the Noise Control Act of 1972, [6] demand for noise barrier design soared from a host of noise regulation spinoff.

By the late 1970s, more than a dozen research groups in the U.S. were applying similar computer modeling technology and addressing at least 200 different locations for noise barriers each year. As of 2006, this technology is considered a standard in the evaluation of noise pollution from highways. The nature and accuracy of the computer models used is nearly identical to the original 1970s versions of the technology.

Small and purposeful gaps exist in most noise barriers to allow firefighters to access nearby fire hydrants and pull through fire hoses, which are usually denoted by a sign indicating the nearest cross street, and a pictogram of a fire hydrant, though some hydrant gaps channel the hoses through small culvert channels beneath the wall.

Design

The acoustical science of noise barrier design is based upon treating an airway or railway as a line source.[ dubious ] The theory is based upon blockage of sound ray travel toward a particular receptor; however, diffraction of sound must be addressed. Sound waves bend (downward) when they pass an edge, such as the apex of a noise barrier. Barriers that block line of sight of a highway or other source will therefore block more sound. [7] Further complicating matters is the phenomenon of refraction, the bending of sound rays in the presence of an inhomogeneous atmosphere. Wind shear and thermocline produce such inhomogeneities. The sound sources modeled must include engine noise, tire noise, and aerodynamic noise, all of which vary by vehicle type and speed.

The noise barrier may be constructed on private land, on a public right-of-way, or on other public land. Because sound levels are measured using a logarithmic scale, a reduction of nine decibels is equivalent to elimination of approximately 86 percent of the unwanted sound power.

Noise barrier earth berm along California State Route 12, Sonoma County, California Noisercrazorback.jpg
Noise barrier earth berm along California State Route 12, Sonoma County, California

Materials

Several different materials may be used for sound barriers. These materials can include masonry, earthwork (such as earth berm), steel, concrete, wood, plastics, insulating wool, or composites. [8] Walls that are made of absorptive material mitigate sound differently than hard surfaces. [9] It is also possible to make noise barriers with active materials such as solar photovoltaic panels to generate electricity while also reducing traffic noise. [10] [11] [12]

A wall with porous surface material and sound-dampening content material can be absorptive where little or no noise is reflected back towards the source or elsewhere. Hard surfaces such as masonry or concrete are considered to be reflective where most of the noise is reflected back towards the noise source and beyond. [13]

Noise barriers can be effective tools for noise pollution abatement, but certain locations and topographies are not suitable for use of noise barriers. Cost and aesthetics also play a role in the choice of noise barriers. In some cases, a roadway is surrounded by a noise abatement structure or dug into a tunnel using the cut-and-cover method.

Disadvantages

Potential disadvantages of noise barriers include:

Effects on air pollution

Roadside noise barriers have been shown to reduce the near-road air pollution concentration levels. Within 15–50 m from the roadside, air pollution concentration levels at the lee side of the noise barriers may be reduced by up to 50% compared to open road values. [14]

Noise barriers force the pollution plumes coming from the road to move up and over the barrier creating the effect of an elevated source and enhancing vertical dispersion of the plume. The deceleration and the deflection of the initial flow by the noise barrier force the plume to disperse horizontally. A highly turbulent shear zone characterized by slow velocities and a re-circulation cavity is created in the lee of the barrier which further enhances the dispersion; this mixes ambient air with the pollutants downwind behind the barrier. [15]

See also

Related Research Articles

<span class="mw-page-title-main">Noise pollution</span> Excessive, displeasing environmental noise

Noise pollution, or sound pollution, is the propagation of noise or sound with ranging impacts on the activity of human or animal life, most of which are harmful to a degree. The source of outdoor noise worldwide is mainly caused by machines, transport and propagation systems. Poor urban planning may give rise to noise disintegration or pollution, side-by-side industrial and residential buildings can result in noise pollution in the residential areas. Some of the main sources of noise in residential areas include loud music, transportation, lawn care maintenance, construction, electrical generators, wind turbines, explosions and people.

<span class="mw-page-title-main">Road surface</span> Road covered with durable surface material

A road surface or pavement is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past, gravel road surfaces, macadam, hoggin, cobblestone and granite setts were extensively used, but these have mostly been replaced by asphalt or concrete laid on a compacted base course. Asphalt mixtures have been used in pavement construction since the beginning of the 20th century and are of two types: metalled (hard-surfaced) and unmetalled roads. Metalled roadways are made to sustain vehicular load and so are usually made on frequently used roads. Unmetalled roads, also known as gravel roads or dirt roads, are rough and can sustain less weight. Road surfaces are frequently marked to guide traffic.

<span class="mw-page-title-main">Acoustical engineering</span> Branch of engineering dealing with sound and vibration

Acoustical engineering is the branch of engineering dealing with sound and vibration. It includes the application of acoustics, the science of sound and vibration, in technology. Acoustical engineers are typically concerned with the design, analysis and control of sound.

<span class="mw-page-title-main">Soundproofing</span> Methods to reduce sound pressure

Soundproofing is any means of impeding sound propagation. There are several basic ways to reduce sound: increasing the distance between source and receiver, decoupling, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles for absorption, or using active antinoise sound generators.

<span class="mw-page-title-main">Architectural acoustics</span> Science and engineering of achieving a good sound within a building

Architectural acoustics is the science and engineering of achieving a good sound within a building and is a branch of acoustical engineering. The first application of modern scientific methods to architectural acoustics was carried out by the American physicist Wallace Sabine in the Fogg Museum lecture room. He applied his newfound knowledge to the design of Symphony Hall, Boston.

<span class="mw-page-title-main">Raised pavement marker</span> Road safety device

A raised pavement marker is a safety device used on roads. These devices are usually made with plastic, ceramic, thermoplastic paint, glass or occasionally metal, and come in a variety of shapes and colors. Raised reflective markers, such as plastic, ceramic, or metal ones, include a lens or sheeting that enhances their visibility by retroreflecting automotive headlights, while glass road studs gather automotive headlights with a dome shape and reflect the lights with a reflective layer within. Some other names for specific types of raised pavement markers include convex vibration lines, Botts' dots, delineators, cat's eyes, road studs, or road turtles. Sometimes they are simply referred to as "reflectors".

<span class="mw-page-title-main">Arterial road</span> High-capacity urban road

An arterial road or arterial thoroughfare is a high-capacity urban road that sits below freeways/motorways on the road hierarchy in terms of traffic flow and speed. The primary function of an arterial road is to deliver traffic from collector roads to freeways or expressways, and between urban centres at the highest level of service possible. Therefore, many arteries are limited-access roads, or feature restrictions on private access. Because of their relatively high accessibility, many major roads face large amounts of land use and urban development, making them significant urban places.

<span class="mw-page-title-main">Cut and fill</span> Earthmoving technique to minimize labor

In earthmoving, cut and fill is the process of constructing a railway, road or canal whereby the amount of material from cuts roughly matches the amount of fill needed to make nearby embankments to minimize the amount of construction labor.

<span class="mw-page-title-main">Sound baffle</span> Device or construct that prevents or attenuates loud noises

A sound baffle is a construction or device which reduces the strength (level) of airborne sound. Sound baffles are a fundamental tool of noise mitigation, the practice of minimizing noise pollution or reverberation. An important type of sound baffle is the noise barrier constructed along highways to reduce sound levels in the vicinity of properties. Sound baffles are also applied to walls and ceilings in building interiors to absorb sound energy and thus lessen reverberation.

In acoustics, noise measurement can be for the purpose of measuring environmental noise or measuring noise in the workplace. Applications include monitoring of construction sites, aircraft noise, road traffic noise, entertainment venues and neighborhood noise. One of the definitions of noise covers all "unwanted sounds". When sound levels reach a high enough intensity, the sound, whether it is wanted or unwanted, may be damaging to hearing. Environmental noise monitoring is the measurement of noise in an outdoor environment caused by transport, industry and recreational activities. The laws and limits governing environmental noise monitoring differ from country to country.

<span class="mw-page-title-main">Noise control</span> Strategies to reduce noise pollution or its impact

Noise control or noise mitigation is a set of strategies to reduce noise pollution or to reduce the impact of that noise, whether outdoors or indoors.

<span class="mw-page-title-main">Atmospheric dispersion modeling</span> Mathematical simulation of how air pollutants disperse in the ambient atmosphere

Atmospheric dispersion modeling is the mathematical simulation of how air pollutants disperse in the ambient atmosphere. It is performed with computer programs that include algorithms to solve the mathematical equations that govern the pollutant dispersion. The dispersion models are used to estimate the downwind ambient concentration of air pollutants or toxins emitted from sources such as industrial plants, vehicular traffic or accidental chemical releases. They can also be used to predict future concentrations under specific scenarios. Therefore, they are the dominant type of model used in air quality policy making. They are most useful for pollutants that are dispersed over large distances and that may react in the atmosphere. For pollutants that have a very high spatio-temporal variability and for epidemiological studies statistical land-use regression models are also used.

<span class="mw-page-title-main">Roadway air dispersion modeling</span> Study of air pollutant transport from a roadway

Roadway air dispersion modeling is the study of air pollutant transport from a roadway or other linear emitter. Computer models are required to conduct this analysis, because of the complex variables involved, including vehicle emissions, vehicle speed, meteorology, and terrain geometry. Line source dispersion has been studied since at least the 1960s, when the regulatory framework in the United States began requiring quantitative analysis of the air pollution consequences of major roadway and airport projects. By the early 1970s this subset of atmospheric dispersion models was being applied to real-world cases of highway planning, even including some controversial court cases.

<span class="mw-page-title-main">Roadway noise</span> Sound energy emanating from motor vehicles

Roadway noise is the collective sound energy emanating from motor vehicles. It consists chiefly of road surface, tire, engine/transmission, aerodynamic, and braking elements. Noise of rolling tires driving on pavement is found to be the biggest contributor of highway noise and increases with higher vehicle speeds.

<span class="mw-page-title-main">AERMOD</span>

The AERMOD atmospheric dispersion modeling system is an integrated system that includes three modules:

<span class="mw-page-title-main">Line source</span> Line from which something (air, noise, radiation, etc.) emanates

A line source, as opposed to a point source, area source, or volume source, is a source of air, noise, water contamination or electromagnetic radiation that emanates from a linear (one-dimensional) geometry. The most prominent linear sources are roadway air pollution, aircraft air emissions, roadway noise, certain types of water pollution sources that emanate over a range of river extent rather than from a discrete point, elongated light tubes, certain dose models in medical physics and electromagnetic antennas. While point sources of pollution were studied since the late nineteenth century, linear sources did not receive much attention from scientists until the late 1960s, when environmental regulations for highways and airports began to emerge. At the same time, computers with the processing power to accommodate the data processing needs of the computer models required to tackle these one-dimensional sources became more available.

The following outline is provided as an overview of and topical guide to air pollution dispersion: In environmental science, air pollution dispersion is the distribution of air pollution into the atmosphere. Air pollution is the introduction of particulates, biological molecules, or other harmful materials into Earth's atmosphere, causing disease, death to humans, damage to other living organisms such as food crops, and the natural or built environment. Air pollution may come from anthropogenic or natural sources. Dispersion refers to what happens to the pollution during and after its introduction; understanding this may help in identifying and controlling it.

CTAG is a computational fluid dynamics model for the behaviour of air pollutants on and near roadways.

Road ecology is the study of the ecological effects of roads and highways. These effects may include local effects, such as on noise, water pollution, habitat destruction/disturbance and local air quality; and the wider environmental effects of transport such as habitat fragmentation, ecosystem degradation, and climate change from vehicle emissions.

References

  1. "UKCA Regulations For Road Noise". 21 December 2023.
  2. Wagner, Kate (8 December 2016). "Building the Wall: Highway Sound Barriers and the Evolution of Noise". 99 Percent Invisible . Retrieved 21 March 2017.
  3. Benz Kotzen and Colin English (1999) Environmental Noise Barriers: A Guide to Their Acoustic and Visual Design, Published by Taylor & Francis, ISBN   0-419-23180-3, 165 pages
  4. John Shadely, Acoustical analysis of the New Jersey Turnpike widening project between Raritan and East Brunswick, Bolt Beranek and Newman, 1973
  5. C.M. Hogan and Harry Seidman, Design of Noise Abatement Structures along Foothill Expressway, Los Altos, California , Santa Clara County Department of Public Works, ESL Inc., Sunnyvale, California, October, 1970
  6. Public Law No. 92-574, 86 Stat. 1234 (1972)Noise Pollution and Abatement Act of 1972, codification amended at 42 U.S.C. 4901-4918 (1988)
  7. PublicResourceOrg (2010-07-31), Highway Noise Barrier Design, archived from the original on 2021-12-19, retrieved 2017-02-04
  8. "4. Noise Barrier Types - Design - Design Construction - Noise Barriers - Noise - Environment". U.S. Federal Highway Administration . Retrieved 2017-01-16.
  9. Reflective and Non-reflective Highway Barriers K. Polcak (MD, SHA) and R.J. Peppin (Scantek, Inc.) case study: Reflective and Non-Reflective Highway Barriers MD SHA) TRB ADC 40 Summer Meeting, Denver, CO
  10. Wadhawan, Siddharth R.; Pearce, Joshua M. (2017). "Power and energy potential of mass-scale photovoltaic noise barrier deployment: A case study for the U.S" (PDF). Renewable and Sustainable Energy Reviews. 80: 125–132. doi:10.1016/j.rser.2017.05.223. S2CID   114457016.
  11. "How Solar Panels Work: Solar Power Science Explained". 7 July 2021.
  12. "Solar power generating noise barriers go up in the Netherlands".
  13. Federal Highway Administration "Highway Traffic Noise" 6/05
  14. Bowker et al., 2007; Baldauf et al., 2008; Heist et al., 2009; Ning et al., 2010; Finn et al., 2010
  15. Bowker, G.E., Baldauf, R., Isakov, V., Khlystov, A., and Petersen, W. (2007). The effects of roadside structures on the transport and dispersion of ultrafine particles from highways. Atmos. Environ. 41, 8128–8139