The difference between sound-absorbing materials and soundproofing materials

The difference between sound-absorbing materials and soundproofing materials. Currently, noise has become a major environmental pollution, and the acoustic environment of buildings is receiving increasing attention and attention. Choosing appropriate materials for sound absorption and insulation treatment of buildings is one of the basic technical measures commonly used in building noise control engineering. However, due to a lack of understanding of noise control methods, sound absorption and insulation, as completely different concepts, are often confused. Materials such as glass wool and rock mineral wool that have good sound absorption performance but poor sound insulation performance are mistakenly referred to as sound insulation materials. In the early years, some sound-absorbing boards made from plant fibers were named sound insulation boards and used to solve the sound insulation problems of buildings. In order to use materials reasonably and improve the noise control effect of buildings, it is necessary to further understand and clarify the concepts of sound absorption and insulation.

The difference between sound-absorbing materials and soundproofing materials is that the sound absorption of materials focuses on the size of the reflected sound energy on one side of the sound source, with the goal of reducing the reflected sound energy. The sound insulation of materials focuses on the size of the transmitted sound energy on the other side of the incident sound source, with the goal of reducing the transmitted sound energy. The attenuation and absorption of incident sound energy by sound-absorbing materials are generally only a few tenths, therefore, their sound absorption capacity, i.e. the sound absorption coefficient, can be expressed as decimals; The sound insulation material can attenuate the transmitted sound energy to 10-3-4 or less of the incident sound energy. For the convenience of expression, its sound insulation amount is expressed in decibels. The difference in material between these two materials is that the absorption material has very little reflection of incident sound energy, which means that sound energy is easy to enter and pass through this material; It can be imagined that the material of this material should be porous, loose, and breathable, which is a typical porous sound-absorbing material. In terms of technology, it usually uses fibrous, granular, or foaming materials to form a porous structure; Its structural feature is that the material has a large number of interconnected micropores from the surface to the inside, which means it has a certain degree of breathability. When sound waves incident on the surface of porous materials, they cause air vibration in the micropores. Due to frictional resistance, viscous resistance of the air, and thermal conduction, a considerable portion of sound energy is converted into heat energy, thereby playing a role in sound absorption. For sound insulation materials, in order to reduce the transmitted sound energy and block the propagation of sound, they should not be as porous, loose, or breathable as sound absorbing materials. On the contrary, their materials should be heavy and dense, such as steel plates, lead plates, brick walls, and other materials. The requirement for sound insulation material material is to be dense without pores or gaps; It has a large weight. Due to the compactness of this type of sound insulation material, it is difficult to absorb and transmit sound energy while reflecting it strongly, resulting in poor sound absorption performance.

In engineering, the goals and focus of sound absorption treatment and sound insulation treatment are different. The goal of sound absorption treatment is to reduce the repeated reflection of sound in the room, that is, to weaken the reverberation sound in the room, and to shorten the duration of reverberation sound, that is, reverberation time; In the case of continuous noise, this weakening manifests as a decrease in indoor noise level, which is when the sound source and sound-absorbing material are located in the same building space. And for the sound transmitted from adjacent rooms, sound-absorbing materials also have an absorption effect, which is equivalent to improving the sound insulation of the enclosure structure.