Curious: What is the main reason for the sound absorption ability of the highway sound barrier?

During the propagation of sound waves, when encountering highway sound barriers, three phenomena of reflection, transmission and diffraction will occur. Prevent the propagation of direct sound, and make the total sound have sufficient attenuation, and the influence of transmitted sound can be ignored. Therefore, the sound insulation effect of the sound barrier can generally be expressed by the amount of noise reduction, which reflects the ability of the above two types of sound transmission of the sound barrier. Insert a sound barrier between the sound source and the receiving point. Set the barrier to be infinitely long. Sound waves can only be diffracted from above the barrier, and a sound shadow area is formed behind it, just as the light is blocked by the object to form a shadow. In this sound and shadow area, people can feel that the noise is significantly reduced, which is the noise reduction effect of the sound barrier.

The road sound barrier is erected between the noise source and the receiver. When the noise is transmitted to the road sound barrier, it will be rebounded, and part of it will be absorbed. So, how does the road sound barrier absorb sound?

1. Glass wool

Centrifugal glass wool is a kind of thermal insulation material that emerged in the 1980s. It is a member of the glass fiber family. It uses international advanced centrifugal blowing technology to fibrillate the glass in a molten state and spray thermosetting resin to make silk wool The material is then heat cured.

Glass wool mainly uses quartz sand, feldspar, sodium silicate, boric acid, etc. as the main raw materials, and is made of glass fiber cotton after high temperature melting.

Product characteristics of glass sound-absorbing cotton: light weight, large sound absorption coefficient, good flame retardant performance and very good chemical stability, and itself is moisture-proof.

2. Aluminum fiber

Aluminum fiber sound-absorbing board is a metal-type sound-absorbing material that is sandwiched between aluminum fiber felt and aluminum foil in the center by a double-sided aluminum plate mesh and rolled. It has excellent sound absorption function, high tensile strength, light material, convenient transportation and good weather resistance.

Aluminum fiber has the following characteristics

Ultra-thin material: The thickness of the aluminum fiber sound-absorbing board is generally between 0.8-2mm, and the density of the board surface is 1.4-3.2kg / m2. Because of its small size and light weight, the transportation

1.35mm thick noise reduction coefficient is 0.7, 1.8mm thick noise reduction coefficient is 0.9

Decorative: Various colors can be sprayed on the board surface, the color is very beautiful, with decorative effect and sound absorption as one.

Convenient processing: The aluminum plate can be processed very well, it is easy to drill, bend and cut. During construction, there will be no fiber dust flying to pollute the environment and affect the health of workers.

3. Aluminum foam

Foam aluminum is made of pure aluminum or aluminum alloy with additives, and is made by foaming technology, and has the characteristics of metal and foaming.

The aluminum foam board has a very good sound absorption function. The average sound absorption coefficient is not more than 0.64, and the noise reduction coefficient is between NRCO.75. It is very good for traffic noise that has been dominated by low and medium frequencies. The aluminum foam surface can be self-cleaned after raining without affecting the acoustic performance.

In summary, it turns out that the road sound barrier material played a key role.