However, 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 "insulation panels". It is also used to solve the sound insulation problem of 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 sound absorption of the material focuses on the amount of sound energy reflected from the sound source side, and the target is that the reflected sound energy is small. The material sound insulation focuses on the amount of transmitted sound energy on the other side of the incident sound source, and the target is that the transmitted 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; and the sound insulating material can attenuate the transmitted sound energy to 10-3 of the incident sound energy. ~10-4 or less, for ease of expression, the amount of sound insulation is expressed in decibels.
The difference in material between the two materials is that 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; it is conceivable that the material of the material should be porous, loose and Breathable, which is a typical porous sound absorbing material, which is usually made of fibrous, granular or foamed materials to form a porous structure; its structural feature is: a large number of interpenetrating materials in the material Micropores from the inside to the inside, that is, have a certain 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 acting as an acoustic absorption.
For sound insulation materials, to weaken the transmitted sound energy and block the sound transmission, 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 plates, lead plates, brick walls, etc. Class materials. The material of the sound insulation 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 absorption performance is poor.
In engineering, the target and focus of sound absorption processing and sound insulation processing 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. That is, the reverberation time; in the case of continuous noise, this reduction is manifested as a reduction in the indoor noise level, which is the same as the construction 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 increasing the sound insulation of the enclosure structure.
The sound insulation treatment focuses on the propagation of noise from the sound source room to the adjacent room to protect the adjacent room from noise.
It can be seen that the effect of insulating noise by using sound insulation material or sound insulation structure is much higher than that of noise absorption material. This means that when the noise source in a room can be separated, the sound insulation measures should be used first; the sound absorption measures should be used when the sound source cannot be separated and the indoor noise needs to be reduced. China Home Theater Network
However, the unique effects of sound absorbing materials are more manifested in the ability to shorten and adjust the indoor reverberation time, which can not be replaced by any other materials. Since 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 adjustment of the sound absorbing material is often indispensable. 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.
Sound absorption and sound insulation are fundamentally different, but in specific engineering applications, they are often combined and have a comprehensive noise reduction effect. In theory, increasing the amount of sound absorption in the room is equivalent to increasing the sound insulation of the partition wall. Commonly there are soundproof rooms, sound insulation covers, composite wall panels composed of plates, sound insulation barriers for traffic trunks, sound insulation 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 sound insulation of the sound insulating structure.
In order to rationally select materials and improve the sound absorption and sound insulation treatment of buildings, firstly, the sound absorption, sound insulation, sound absorption materials and sound insulation materials are conceptually distinguished, which should be the primary basic in building noise control. problem
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