Due to the lack of understanding of the means of noise control, "sound absorption" and "sound insulation" are often confused as completely different concepts. Glass wool, rock and mineral wool, which have good sound absorption properties but poor sound insulation properties, have been mistakenly called "sound insulation materials". In the early years, some sound-absorbing panels made of plant fibers were named "sound insulation panels" and were used to solve them. Sound insulation problems in buildings... In order to rationally use materials and improve the noise control effect of buildings, it is necessary to further understand and clarify the two concepts of “sound absorption†and “sound insulationâ€.
The difference between material sound absorption and material sound insulation is that the material sound absorption focuses on the amount of reflected sound energy on the side of the sound source, and the target is that the reflected sound energy is small. The absorption and absorption of the incident sound energy by the sound absorbing material is generally only a few tenths. Therefore, the sound absorbing ability, that is, the sound absorbing coefficient, can be expressed by a decimal number; the material sound insulation focuses on the size of the transmitted sound energy on the other side of the incident sound source, and the target is the transmitted sound. Can be small. The sound insulating material can attenuate the transmitted sound energy to 10-3 to 10-4 or less of the incident sound energy. For the convenience of expression, the sound insulation amount is expressed by a decibel metering method.
The difference in material between the two materials is:
The sound absorbing material has little reflection on the incident sound energy, which means that the sound energy can easily enter and penetrate the material; the material of the material should be porous, loose and breathable, which is a typical porous sound absorbing material in the process. Generally, a fibrous, granular or foamed material is used to form a porous structure; the structural feature is that the material has a large number of interpenetrating micropores from the inside to the inside, that is, a certain gas permeability. When sound waves are incident on the surface of the porous material, the air in the micropores is caused to vibrate. Due to the frictional resistance and the viscous resistance of the air and the heat conduction, a considerable part of the acoustic energy is converted into heat energy, thereby functioning as a sound absorbing.
The sound-insulating material can reduce the transmission sound energy and block the transmission of sound. It cannot be as porous, loose and breathable as the sound-absorbing material. On the contrary, its material should be heavy and dense, such as steel plate, lead plate, brick wall and so on. The material of the soundproof material is dense and has no pores or gaps; it has a large weight. Since such a sound-insulating material is dense, it is difficult to absorb and transmit sound energy and the reflection energy is strong, so its sound absorbing performance is poor.
In engineering, the target and focus of sound absorption treatment and sound insulation treatment are different. The goal of sound absorption processing is to reduce the repeated reflection of sound in the room, that is, to reduce the reverberation sound in the room and shorten the duration of the reverberation sound, ie reverberation. Time; in the case of continuous noise, this reduction is manifested by a reduction in the indoor noise level, which is the same as the building space where the sound source and the sound absorbing material are located. The sound absorbing material also absorbs the sound transmitted from the adjacent room, which is equivalent to improving the sound insulation of the enclosure structure.
Sound insulation is focused on the isolation of noise from the source room to adjacent rooms to protect adjacent rooms from noise.
It can be seen that the use of sound-insulating materials or sound-insulating structures to isolate noise is much higher than that of sound-absorbing materials. This means that when noise sources in a room can be separated, sound insulation should be used first; sound absorption measures should be used when the sound source cannot be separated and the indoor noise needs to be reduced.
The unique role of sound absorbing materials is more manifested in the ability to shorten and adjust the indoor reverberation time, which can not be replaced by any other materials. Because the volume of the room is proportional to the reverberation time, the large building space has a long reverberation time, which affects the indoor listening conditions. At this time, the reverberation time of the sound absorbing material is often inseparable. For large halls such as cinemas, conference halls, concert halls, etc., according to their different listening requirements, appropriate sound-absorbing materials can be selected, and the reverberation time can be adjusted according to the body shape to achieve different subjective feelings such as clear and full listening. From this point of view, the sound absorbing material shows its unique importance, so the acoustic material usually referred to is the sound absorbing material. China Home Theater Network welcomes you to have a fundamental difference between sound absorption and sound insulation, but in specific engineering applications, they are often combined and have a comprehensive noise reduction effect. In theory, increasing the suction volume in the room is equivalent to increasing the sound insulation of the partition wall. Commonly, there are soundproof rooms, soundproof covers, composite wall panels composed of plates, noise barriers for traffic trunks, soundproof screens in workshops, pipe wrapping, and so on. Sound absorbing materials, if used alone, can absorb and reduce the noise of the room where the sound source is located, but cannot effectively isolate noise from the outside world. When the sound absorbing material and the sound insulating material are used in combination, or the sound absorbing material is used as a part of the sound insulating structure, the advantageous result is generally manifested as an increase in the soundproofing of the sound insulating structure.
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