What Is the Sound Barrier?

Sound barriers are mainly used for sound insulation and noise reduction of highways, highways, elevated composite roads and other noise sources. It is divided into reflection-type sound barriers with pure sound insulation, and composite sound barriers that combine sound absorption and sound insulation. Refers to the wall structure on the side of railways and highways to reduce the impact of traffic noise on nearby residents. Sound insulation walls are also called sound barriers. A facility is inserted between the sound source and the receiver, so that the sound wave propagation has a significant additional attenuation, thereby reducing the impact of noise in a certain area where the receiver is located. Such a facility is called a sound barrier. Divided into traffic noise barriers, equipment noise attenuation noise barriers, industrial plant boundary noise barriers, highways and highways are the most commonly used types of noise barriers ^[1] .

Outdoor sound barriers generally use brick or concrete structures.

1. Thermal insulation performance: Good thermal insulation performance is the basic characteristic of rock wool products. The thermal conductivity of rock wool is usually between 0.03 and 0.047 W / (moK) under normal temperature conditions (about 25 ° C).

2. Combustion performance:

Sound absorption

Product features of pinhole composite sound-absorbing aluminum plate: light weight, no pollution, anti-glare, anti-aging, impact resistance, freeze-thaw resistance, stable sound absorption coefficient, moisture resistance, corrosion resistance, easy bending, easy processing, easy transportation, convenient disassembly and maintenance , Reasonable price, and can spray a variety of colors.
Technical parameters of pinhole compound sound aluminum plate:
1. Noise reduction coefficient: NRC 0.70 at 75MM cavity;
2. Sound insulation: 30dB (A);
3. Artificial accelerated weather resistance (250h): no chalking;
4. Salt spray corrosion resistance: 1000h acidity, grade 10 appearance, no pitting, blistering, peeling and other corrosion phenomena;
5. Tensile load: 1305N;
6. Fire rating: Class A non-combustible

Cement sound absorption

High-strength cement-based lightweight composite sound-absorbing and sound-insulation barrier: Light-weight high-strength cement sound-absorbing and sound-absorbing panels adopt advanced technology and raw materials to produce high-efficiency sound-absorbing and noise-reducing products with technical performance at the domestic advanced level. Various types of structures and beautiful appearance. Can meet different design requirements, widely used in highways, railways, viaducts and industrial plant boundary noise control projects.

Slate sound absorption

Perlite is a fine-pored, inorganic cement composition. It does not contain pollutants. It is basically cement, natural minerals, and other chemical materials. After special treatment, it is stirred and molded to make it durable and highly malleable. It can be adjusted to different bulk density, shape, color and appearance to suit different installation and design conditions, which can meet the different needs of practical applications. Compared with other existing sound absorption and sound insulation materials, perlite materials have the following characteristics:

Perlite sound barrier has stable sound absorption performance, with a noise reduction coefficient of about NRC 0.85. It has good sound absorption performance in the high-frequency section of noise and meets the acoustic requirements of road sound barriers.

Simple application and installation, can be prefabricated or formed in the field.

No organic ingredients, no pollution ingredients: for example, asbestos, mineral fibers,

The noise reduction of the sound barrier is related to the frequency of the noise, the height of the barrier, and the distance between the sound source and the receiving point. The noise reduction effect of the sound barrier has a great relationship with the frequency components of the noise. The high-frequency sound greater than 2000 Hz has a better noise reduction effect than the intermediate frequency sound of about 800-1000 Hz, but for low-frequency sound of about 25 Hz. Because the wavelength of the sound wave is relatively long, it is easy to diffract through the barrier, so the effect is poor. Generally, the sound barrier can reduce l0-15dB for high frequency sound. The height of the sound barrier can be designed according to the distance between the sound source and the receiving point. If the height of the barrier is doubled, the amount of noise reduction can increase by 6dB. Source or receive point.

1. Sound waves People call the mechanical waves that can cause hearing sound waves (audio). The frequency is between 20 and 20000 Hz.

2. Mechanical waves with infrasound frequencies below 20 Hz are called infrasound waves.

3. Mechanical waves whose ultrasonic frequency is higher than 20000Hz are called ultrasonic waves.

4. Waves in which the particles move in the direction of propagation in longitudinal wave media.

5. Particles in transverse wave media are waves that move perpendicular to the direction of propagation.

6. Surface waves are waves that propagate along the surface layer of the medium and whose amplitude decreases rapidly with depth.

7. Plane wave wave front is a wave whose plane is perpendicular to the direction of propagation.

8. Cylindrical wave fronts are coaxial cylindrical waves.

9. Spherical wave fronts are concentric spherical waves.

Sound barriers are mainly used along railways and highways,

Sound barriers are mainly used for sound insulation and noise reduction in transportation and municipal facilities such as expressways, elevated composite roads, urban light rail subways, etc.

The general principles for the selection of sound barrier materials are good noise reduction performance, safe and reliable structure, economical materials, low installation costs, durability, long service life, harmonious landscape, elegant appearance and so on. The details are as follows:

(1) Large sound insulation: The average sound insulation should not be less than 35dB;

(2) High sound absorption coefficient:

1. The sound barrier foundation built on the subgrade shall be constructed simultaneously with the subgrade, and shall not be damaged due to its construction, affecting the stability and safety of the subgrade. The foundation construction of the sound barrier should be performed after the road basic body is formed, before the track is laid and the cable groove is constructed. Before construction, the positions of various pipelines on the roadbed should be checked. According to the foundation size of the sound barrier and its position on the shoulder of the road, cut and slot, It is strictly forbidden to damage all kinds of pipelines when the tank is slotted.

2. The sound barrier foundation shall be constructed in accordance with the design requirements of location, shape, size and depth. The excavation of the foundation shall not damage the surface of the foundation bed.

3. The materials and construction methods used in the construction of sound barrier foundation buried anchor rod and anchor hole grouting shall meet the design requirements and shall not affect the safety and stability of the roadbed.

4. The sound barrier foundation should be constructed with expansion joints according to design requirements. An expansion joint is set for the sound barrier foundation every 20m ~ 30m long. The specific expansion joint position should be determined during the construction according to the site terrain.

5. The sound barrier foundation shall be embedded with drainage pipes in accordance with design requirements, and the drainage outlet shall not scour the subgrade; the foundation concrete construction at the intersection with the drainage well of the water collecting well between the ballastless track line shall not damage the drainage pipes. Every 2m of the foundation is embedded with & oslash; 100mm L-shaped PVC pipe to discharge rainwater on the shoulder of the road inside the sound barrier; every 4m in the middle of the foundation is embedded with & oslash; 75mm straight PVC pipe at a 2% slope to eliminate the water leakage and The cable trough is leaking water; the connection drainage pipe of the water collecting well between the baselines of the ballastless track line can be poured into the foundation. The subgrade sound barrier should be provided with drainage facilities, and the outer drainage outlet should avoid scouring the subgrade slope and prevent sound leakage.

6. After all the sound barrier foundation is filled with concrete and compacted, its surface should be smooth with the subgrade surface.

7. The strength test of sound barrier foundation concrete shall comply with the provisions of Article 11.2.18 of this standard.

8. The gap between the sound barrier foundation and the cable trough, the catenary support pillars, and the road shoulder surface should be waterproofed according to the design requirements. Asphalt concrete is used as the waterproof layer between the foundation and the cable trough, the gap between the catenary struts and the gap between the road shoulder.

9. The position of the sound barrier foundation from the center line of the line, the cross-sectional size, the allowable deviation of the embedment depth , the number of inspections and the inspection methods shall comply with the requirements of Table 13.4.9.

Advantage prospects

Advantage:

1. Low cost: Not only the low production cost of the product, but also the light weight of the product can greatly reduce the load-bearing load of the elevated light rail and elevated road and reduce the cost of the project;

2. Strong wind load: high strength and light weight, which can meet the requirements of wind load under different climatic conditions in various regions of China;

3. Superior acoustic performance: The average sound insulation of magnesite sound barrier is greater than 35dB and the average sound absorption coefficient is greater than 0.84, which meets the requirements of sound barriers in various fields;

4. Good fire resistance: Magnesite cementitious materials are inorganic incombustible materials, and composite sound-absorbing glass wool, perlite and other materials also have good fire resistance, which makes the products have excellent fire resistance, which is a national class A incombustible material;

5. Good durability: Magnesite sound barrier is water-resistant, fire-resistant, corrosion-resistant, UV-resistant, and is not affected by harsh weather such as rain, snow, wind, and sand, and has a long service life;

6. Easy installation: Magnesite sound barrier is light in weight, can be assembled for construction, has high efficiency, short construction period, and can save a lot of labor costs;

7, beautiful and plastic: according to different needs can be used in combination with metal materials and light-transmitting structural forms, can also be sprayed with various colors and patterns to achieve landscape decoration requirements.

8. Energy saving and environmental protection: The raw materials used for magnesite sound barrier are non-toxic and harmless, and the production process does not require high-temperature heating and no toxic gas release. It is an environmentally-friendly product encouraged by the country;

9. Wide application range: According to different needs, it can process and produce magnesite sound insulation board and magnesite sound-absorbing board. It is suitable for highways, light rails, railways, culverts, tunnels and other transportation fields, as well as various industrial plants, workshops and residential areas.

Prospects: With the rapid development of China's economy and the acceleration of urbanization, transportation methods such as expressways, railways, and urban rail transit have developed rapidly. These roads will inevitably pass through densely populated residential areas during construction. Traffic noise has caused some interference to the work, life and study of residents near the road. National environmental monitoring results show that about 17% of cities with road traffic noise are moderately polluted and 49% of cities are lightly polluted. Establishing sound barriers to solve traffic noise pollution has become the main way to control urban road noise. Magnesite sound barriers have developed rapidly due to their unique advantages and have been widely used in cities such as Beijing, Zhengzhou, Guangzhou and Chongqing.

1.Diffraction

The sound energy that is diffracted across the top of the sound barrier to the receiving point is lower than the direct sound energy when there is no barrier. The difference between the sound level of the direct sound and the diffraction sound is called the diffraction sound attenuation, and its value is represented by the symbol Ld, and it increases with the increase of the angle. The diffraction sound attenuation of the sound barrier is a function of the geometric relationship and frequency of the sound source, the receiving point and the sound barrier, and it determines the height of the sound barrier.

2. Transmission

The phenomenon that the sound wave from the sound source is transmitted to the receiving point through the sound barrier. The sound energy that penetrates the sound barrier depends on the areal density of the sound barrier, the angle of incidence, and the frequency of the sound wave. The ability of the sound barrier to isolate sound is evaluated by the sound transmission loss TL. The larger the TL, the smaller the transmitted acoustic energy; the smaller the TL, the larger the transmitted acoustic energy. The transmitted acoustic energy may reduce the insertion loss of the sound barrier. The reduction in the insertion loss due to transmission is called the transmitted sound correction amount. It is represented by the symbol Lt. Usually in the acoustic design, TL- Ld 10dB is required, and the transmitted sound energy can be ignored, that is, Lt0.

3.Reflection

When there are sound barriers on both sides of the road, and the sound barriers are parallel, the sound waves will be reflected between the sound barriers multiple times and diffracted across the top of the sound barrier to the sound receiving point. The amount of reduction in the insertion loss is called the reflected sound correction amount, and is represented by the symbol Lr.

In order to reduce the reflected sound, a sound-absorbing structure is generally added to the side of the sound barrier on the side of the road. The amount of reflected sound energy depends on the sound absorption coefficient of the sound absorption structure, which is a function of frequency. In order to evaluate the overall sound absorption effect of the sound barrier sound absorption structure, the noise reduction coefficient NRC is usually used. The main physical quantity of barrier insertion loss ^[1] .