This article discusses Noise Barrier and covers the following key topics:
- Types of noise barriers
- Standards and testing of noise barriers
- Design principles for noise barriers
It emphasizes noise pollution as a major issue in urban development, especially near highways, bridges, and railways. The article highlights collaboration between government, academia, and private sectors to develop effective noise barrier standards, using suitable materials, including agricultural and recycled options.
Types of Noise Barriers
1. Reflective Barriers
These barriers function by reflecting sound away from protected areas. They are typically made from smooth materials such as fiber-reinforced cement, metals, or composite plastics, which are effective in sound reflection.
Illustration from IAC Acoustics
Example of using a reflective wall
Illustration from the Department of Highways
2. Absorptive Barriers
These barriers are designed to reduce sound reflection by using sound-absorbing materials, such as fiber-based or porous panels. They are ideal for areas with significant sound reflection, such as urban environments or locations with reflective surfaces.
Example of using sound-absorbing walls
Illustration from the Department of Highways
3. Combination Barriers
These barriers combine the properties of both reflective and absorptive barriers, allowing them to both block and absorb sound. This dual functionality makes them effective in a variety of environments where both sound reduction and absorption are needed.
Illustration from IAC Acoustics
Design an effective noise barrier
Key factors include the height and length of the wall, tailored to the sound source and the area to be protected. In projects like Thailand’s Highway 9, acoustic simulations are conducted before installation to predict how much noise reduction (in decibels) the barrier will provide under real-world conditions. This ensures the barrier’s effectiveness before actual deployment.
Example image of a noise barrier on a highway in Europe
Example image of a sound barrier of a train in Singapore
Source: https://www.geonoise.com/noise-barriers-for-lta-in-singapore/
Image of a sound barrier design in Taiwan that prevents birds from flying into passing vehicles.
Source: https://www.geonoise.com/taiwan-highway-to-get-noise-barrier-to-protect-birds/
Example images of in-situ testing of a barrier wall according to ISO 10847 and acoustic simulation.
For walls that are installed at the actual site or simulate outdoor installation, they can also be tested for acoustic properties, that is, by measuring the Sound Insertion Loss (SIL) value using the ISO 10847 test standard to see the sound attenuation when passing through the wall as shown in the image above. Currently, there is also technology to test the sound absorption value in-situ or testing in a format where a real wall has been installed at the site using the Local Plan Wave method that uses an Array microphone to scan the surface of the material to measure the sound wave absorption value.
Image of sound barrier test using SONOCAT instrument
Peeters, F., Peeters, B., & Wijnant, Y. (2016). Determination of Acoustic Properties of Noise Barriers
Soundproof wall testing standards
Noise barriers can be tested in laboratories according to standards like ISO 10140-2, EN1793, or ASTM E90, measuring Sound Transmission Loss (STL) across frequencies (e.g., 125Hz to 4000Hz). The results are processed into a rating that indicates the material’s soundproofing performance. In Thailand, testing can be done at ALT Acoustic Laboratory Thailand. But when using sound barriers in real environments, one important thing to consider when evaluating how much sound a wall can block is testing the Sound Insertion Loss (SIL) value using the ISO 10847 test standard. The principle is to measure the difference between with and without a wall. The test standard specifies the distance of the microphone installation and the reference microphone point, as well as the selection of the sound source.
Illustration from Acoustic Laboratory Thailand Co., Ltd.
In addition, some types of walls that are designed to absorb sound waves or absorb sound, Sound absorption, can also be tested for these values in the laboratory, which will use the ISO354 or ISO11654 or ASTM E423 test standards, using a reverberation chamber or echo chamber in the test, which will be tested as the coefficient of sound absorption NRC and the Sound absorption value at each frequency.
Soundproof wall design principles
To effectively protect against noise, we need to take the following important steps:
1. Assess the noise situation
We need to know the noise level that needs protection by measuring the noise level in the affected area or checking from noise complaints from nearby communities. This assessment will help us understand the nature of the problem and clearly define the scope of the sound barrier wall design.
2. Choose the right sound barrier materials
The selection of materials used to build sound barriers is the key. Sound barrier materials can be divided into 2 main types:
Reflective Materials: Help reflect sound back to the direction of the sound source, reducing the spread of sound to areas that need silence.
Absorptive Materials: Reduce the sound that hits the wall by absorbing sound to reduce echoes and reverberations.
Alternative Materials can also be considered with special properties, such as composite materials or materials that have been tested in the laboratory for acoustic properties or Acoustic Engineering calculations to maximize the sound barrier efficiency.
3. Using Mathematical Modeling (SoundPLAN Modeling)
SoundPLAN is a sound simulation tool that is widely used in many countries, including in Thailand. Using SoundPLAN helps to design sound barriers accurately by analyzing data and creating mathematical models that simulate real situations, using calculations according to the ISO 9613-2 standard.
This software is used by leading organizations such as:
- Department of Highways and Expressway Authority of Thailand: for the design and installation of sound barriers in expressway and highway projects
- Large construction companies: for construction projects that require noise reduction from construction projects
- Environmental consulting firms: for Environmental Impact Assessment (EIA)
- Academic institutions and research: for the research and development of new soundproofing technologies
Designing with SoundPLAN allows you to see the results of sound barriers before actual construction, allowing us to improve and customize the design for maximum efficiency, meeting both efficiency and cost-effectiveness.
The modeling process involves various types of sound analysis. Result Analysis After the simulation, SoundPLAN generates noise maps and graphs showing the noise reduction results:
- Noise Contour Maps: Shows the noise levels in the area before and after the installation of the sound barrier
- Community Impact Analysis: Helps assess whether the sound barrier can reduce noise levels below a specified threshold
- Sensitivity Analysis: Helps improve the design by analyzing how changes in the material or size of the barrier affect the noise reduction.
SoundPLAN allows you to optimize and improve the efficiency of your sound barrier based on the analysis:
- Wall size and shape adjustment: Adjust the height, thickness, and length of the wall to achieve maximum efficiency.
- Appropriate material selection: If the analysis shows that the selected material does not reduce the noise as desired, you can choose a material with better sound absorption or sound insulation properties.
- Cost Analysis: Assess the cost of construction and materials to make the design cost-effective and budget-saving.
In many projects where acoustic consultants are hired to calculate and design according to the principles mentioned above, it is possible to ensure that the sound barrier wall that is installed is of the highest efficiency and also helps save unnecessary budget.