[Home Theater Network HDAV.com.cn] Room acoustic design is a system discipline with a wide range of aspects. Its acoustic principle comes from physical acoustics, and at the same time it is blended with materials science, psychology, architecture, etc. The human and listening environment is at the core, focusing on the scientific branch of the hall sound quality and noise control. In order to ensure the sound quality of the interior, especially the audio-visual space, it is necessary to properly design the acoustics and arrange the decorative materials correctly according to different acoustic properties. Basic concepts of sound absorption and sound insulation We know that when a sound encounters a large barrier in the transmission path, part of its energy is reflected by the barrier, another part is absorbed by the material, and some part is transmitted to the other side through the barrier, so It has created two different acoustic concepts of sound absorption and sound insulation, as follows: Completely different in acoustics Sound absorption refers to the use of sound absorbing materials or sound absorbing structures to absorb the incident sound energy and reduce the reflected sound, thereby reducing the noise inside the volume. Sound insulation is to use sound insulation structure to block the sound, reduce the transmission of noise, and separate the noise environment from the environment that needs to be quiet. For example, noise reduction box, sound insulation room, sound insulation screen, etc. are commonly used sound insulation devices. . The privacy of the indoor environment has been guaranteed to reduce the influence of external sounds. Sound absorption and sound insulation measures are different What is paying attention to sound absorption is the amount of sound energy reflected back on the barrier side. The smaller the reflected sound, the better the sound absorption effect of the clothing; the sound insulation pays attention to the amount of sound energy transmitted through the other side of the barrier. The smaller the sound energy, the better the sound insulation effect. In specific applications, the use of sound insulation materials or sound insulation to isolate noise is much higher than the noise reduction effect of sound absorbing materials. 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. Sound absorption and sound insulation are different materials The sound absorption uses a lot of bulky and porous materials, and the sound insulation uses a dense and non-breathable material. Sound absorbing material and sound insulation material For a single acoustic material (not a specially designed composite), the sound absorption and sound insulation effects are often not compatible. Such as brick walls or steel plates, although it can be used as a sound insulation material, but the sound absorption effect is very poor; in turn, if a sound-absorbing material (such as glass wool) is used as a sound insulation material, even sound waves pass through the material. When the sound can be absorbed by 99% (this is difficult to achieve), only 1% of the sound energy is transmitted to another space, then the sound insulation of this material is only 20dB, which is not a good sound insulation material. Therefore, it is wrong to mistake the sound absorbing material as "sound insulation material". Sound absorbing material Sound absorbing materials refer to building decoration materials with relatively high sound absorption coefficient. If there are many inter-connected fine spaces inside the material, the air passage formed by the voids can be modeled as a duct structure composed of a plurality of thin tubes or capillaries formed between the solid frames. When the sound wave is introduced, the acoustic vibration velocity in the thin tube near the tube wall and the tube is different, and the internal friction caused by the velocity difference between the media causes the acoustic vibration energy to be converted into heat energy and absorbed. Good sound absorbing materials are mostly fibrous materials, called porous sound absorbing materials, such as glass wool, rock wool, mineral wool, cotton and rayon cotton, special metal fiber cotton, etc., including foams with voids. Plastic and the like. The sound absorption performance is related to the fiber void structure of the material, such as the thickness of the fiber (better to tens of micrometers) and the material density, the ratio of the air volume to the volume of the material (called the void ratio, and the porosity of the glass wool is 90). % or more), the shape and structure of the voids in the material, and the like. From the point of view of use, regardless of the mechanism of sound absorption, it is sufficient to consult the experimental results of the sound absorption coefficient of the material. Of course, we must pay attention to other requirements such as moisture, fire and decorative. Generally, the low-frequency sound absorption performance of flat sound-absorbing materials is a common law. An improved method is to cut a monolithic sound absorbing material into a pointed shape. When the sound wave propagates to the pointed material, the ratio of air to material gradually changes from the tip to the base, that is, the acoustic impedance gradually changes, and the sound wave propagates beyond the limit of the effective thickness of the flat material to reach the base of the material. Improve low frequency sound absorption performance. Of course, such sound absorbing structures are generally not suitable for interior decoration, and are mainly used in acoustic laboratories or special noise control projects. Resonance sound absorption structure The resonant sound absorption structure uses different resonance sound absorption mechanisms to design various types of resonance sound absorption structures, so that the absorption peak is selected at the desired frequency position, and the sound absorption amount of different frequencies is satisfied, especially the low frequency sound absorption is insufficient. problem. Mainly use several professional structural clothes to achieve the sound absorption effect: the resonance sound absorption of the thin layer porous sound absorbing material, the film resonance sound absorption, the thin plate resonance sound absorption, and the perforated plate resonance sound absorption structure. Sound insulation material The airtight solid material has sound insulation effect on the sound waves propagating in the air. The most fundamental point to determine the sound insulation effect depends on the mass per unit area of ​​the material. The spacer material has a certain physical elasticity, and when the sound wave is incident, the vibration is excited to propagate in the interlayer. When the sound wave is not perpendicular to the incident, but is incident at an angle θ with the interlayer, the acoustic wavefront reaches the surface of the interlayer in turn, and the bending vibration wave in the acoustic excitation barrier of the first layer propagates laterally along the interlayer, if the bending wave When the speed of propagation coincides with the speed at which the sound waves in the air gradually reach the surface of the partition, the sound waves enhance the vibration of the bending waves. This phenomenon is called an anastomosis effect. At this time, the vibration of the bending wave is particularly large, and the energy of radiating the sound wave to the other side of the air is also particularly large, thereby reducing the sound insulation effect. Double layer sound insulation structure According to the law of mass, the frequency is reduced by half, and the transmission loss is reduced by 6 dB. When the sound insulation effect is improved, the mass is doubled and the transmission loss is increased by 6 dB. Under the control of this law, if the sound insulation ability is to be significantly improved, it is obviously impossible to increase the quality of the partition, such as increasing the thickness of the wall, sometimes it is impossible, such as the sound insulation structure on the aircraft. . At this time, the solution is mainly to use a double layer or even a multilayer sound insulation structure. Generally, two layers of double-layer sound insulation structure do not use the same material of the same thickness to avoid the same frequency of matching between the two layers. At the same time, special attention should be paid to the design and construction. There should be no rigid connection between the two layers. The two-layer structure of "solid-air-solid" is destroyed, and the two layers of solid partitions are connected by rigid members, so that the vibrations of the two partitions are connected together, and the sound insulation is greatly reduced. Especially for double-layer light structure sound insulation, when they must support or connect each other, they must be supported or suspended by elastic members, and at the same time, note that there is no seam or hole communication between the two spaces that need to be divided. "Leaking gas" is going to leak sound, which is the actual problem of sound insulation. Both sound absorption and sound insulation are important technical measures in noise control. The two have essential differences, but they are related to each other in practical applications, and exert comprehensive sound field optimization and noise control effects. Therefore, firstly, the sound absorption, sound insulation, sound absorption materials, and sound insulation materials are conceptually distinguished, and materials are reasonably selected to improve the sound absorption and sound insulation treatment effects of buildings, and the audio and video industry can be better consolidated. The technical strength of practitioners in the field of private custom installations to better serve consumers. More fresh and fun home theater information, please pay attention to home theater network (WeChat: cnhifi) http://, the country's most influential home theater audio player interactive media website. Note: This article is transferred from the new era of audio and video. The article is an independent view of the author and does not represent the position of the home theater network. 6.2Mm Ribbon Connector,Wire-To-Wire Connector,Ket Connectors,6.2Mm Ribbon Connectors YUEQING WEIMAI ELECTRONICS CO.,LTD , https://www.wmconnector.com
