[Home Theater Network HDAV.com.cn] A good hall, in order to get good sound quality, architectural acoustic design must meet two conditions: the appropriate intermediate frequency reverberation time and the ideal reverberation time curve. Therefore, we need to carefully select different acoustic materials during the renovation process. A variety of acoustic decoration materials can not only create an excellent acoustic environment for us, but also bring a wonderful sound. At the same time, the fashionable design and rich colors also bring us artistic visual enjoyment.
Overview
The sound absorbing material refers to a material having an average sound absorption coefficient of more than 0.2 for the frequency. Most of the sound absorbing materials are loose and porous materials such as slag wool and blankets.
The role of sound absorbing materials and sound absorbing structures:
1. Shorten and adjust the reverberation time;
2. Control the reflected sound;
3. Eliminate echoes;
4. Improve sound quality and change the sound field distribution.
working principle
Since the sound originates from the vibration of the object, it causes vibration of the adjacent air to form an acoustic wave and propagates around in the air medium. The sound absorbing material is that when the sound is transmitted to the surface of the member material, part of the sound energy is reflected, a part of the sound is penetrated, and a part is rubbed into the heat energy by the vibration of the material or the sound of the sound in the surrounding medium. The sound energy is lost, that is, the sound is usually absorbed by the material.
Sound absorption coefficient :
The sound absorption performance of the material is represented by the sound absorption coefficient α. Α is the sum of the loss factor E/E0 and the penetration coefficient E/E0.
The sound absorption properties of the material are related to the structure, thickness and surface characteristics of the material, as well as the direction and frequency of the sound.
application
Sound absorbing materials are commonly used for indoor volume and sound quality control. The larger the room size, the longer the reverberation time, the worse the speech intelligibility. In order to ensure the clarity of the language, it is necessary to do sound absorption indoors and control the reverberation time. Such as auditoriums, classrooms, stadiums, cinemas.
The requirements for sound-absorbing materials used in music architecture are stricter. The use of sound absorbing materials is to ensure a certain fullness of the sound and to properly extend the reverberation time. In order to prevent acoustic defects such as echo, acoustic feedback, and sound focusing, sound absorbing materials can be used on the rear wall surface, the second floor railing surface, the side wall surface, and the part.
The sound absorbing materials used in the design of the acoustic environment of the building also need to consider the use of materials comprehensively, including sound absorption performance and decorative, strength, fireproof, moisture absorption, processing and many other aspects.
Structure type of sound absorbing material
There are many types of sound absorbing materials and structures. According to their different material structures, they can be divided into the following categories:
(1) Porous sound absorbing material: fibrous sound absorbing material, granular sound absorbing material, foamy sound absorbing material;
(2) Resonance sound absorption structure: single resonator, perforated plate resonance sound absorption structure, thin plate resonance sound absorption structure;
(3) Special sound absorption structure: thin film resonance sound absorption structure;
Types of
Resistive decay type
Resistant attenuating soft porous materials are widely known as glass wool and rock wool; rigid porous materials are metal, ceramic, synthetic resin porous materials, among which aluminum sound absorbing materials have received attention. The reason is that the porous metal material is a rigid body, and it is not necessary to protect the perforated surface layer material like a soft porous material, and it will not aging or scattering to pollute the environment for a long time, and the sound absorption coefficient after moisture absorption or wetting will not affect its sound absorption performance. .
Film vibration type
The film vibration type sound absorbing material is usually attached to other materials such as aluminum foil in an aluminum fiber sound absorbing material. There is also a micro-perforated polyethylene film that can be attached to the glass of a normal window. Sound absorption performance: It has excellent mid-frequency sound absorption characteristics.
Space sound absorber
The difference between a spatial sound absorbing body and a general sound absorbing structure is that it is not combined with a rigid wall such as a ceiling or a wall surface to form a sound absorbing structure, but is self-contained. The indoor sound absorption treatment generally installs the sound absorbing materials on the indoor and outdoor surfaces in the construction and decoration. However, it can be prefabricated as a sound absorbing member: a spatial sound absorbing body for on-site lifting. In essence, the sound absorbing body is not a new sound absorbing structure, but the sound absorbing characteristics are different due to different use conditions. Hanging in a position where the sound energy flow density is large (for example, near the sound source and where the reflection is focused) can achieve better results.
Strong sound absorption
The sound absorbing tip is a strong sound absorbing structure commonly used in the anechoic chamber, and the interface is tiled porous material.
Curtain
The curtain has a certain distance from the wall and the window glass, just like the air layer is placed behind the porous material. Although it is not completely closed, it has a certain sound absorption effect on the medium and high frequency.
Hole
The opening to the outdoor free sound field is completely sound-absorbing from the indoor point of view, and the sound absorption coefficient is 1 for all frequencies. It has a greater impact on room acoustics. If the hole is not facing the free sound field, its sound absorption coefficient is less than 1.
People and furniture
People and furniture can also absorb sound, so people and furniture are actually sound absorbing bodies. A general sound absorbing material and structure can determine the suction volume by the product of its sound absorption coefficient and effective area. Therefore, the sound absorption characteristics are expressed by the suction volume of each person or each piece of furniture, and the product of the number (or the number of pieces) is the total suction volume.
With the rapid development of modern science and technology, the types and functions of acoustic materials will increase. In order to meet the growing needs of people for sound absorbing materials, the application of sound absorbing materials will become more and more widespread.
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