Noise pollution, one of the three major public hazards in the contemporary world, has become the common enemy of mankind. Therefore, sound absorption and noise reduction has become an important issue related to high technology, environmental governance and human development that needs to be solved urgently. As a passive control method The acoustic material used has also become one of the main methods to solve the problem of sound absorption and noise reduction, and the structure, acoustic properties and application of acoustic materials are complex issues involving multiple disciplines. Therefore, this paper attempts to summarize the achievements in the application research of new acoustic materials in the past ten years, find out the deficiencies, point out the direction of future research efforts and put forward relevant suggestions for reference by the industry.
No.1 Types of acoustic materials and sound-absorbing principles
acoustic materials refer to sound-absorbing acoustic materials that can be used to reduce noise (<1kHz), improve the sound environment, and convert sound energy into heat energy. It has been widely used in industrial enterprises, urban transportation, public buildings and media communication industries. In engineering applications, people usually divide acoustic materials into the following types: such as porous acoustic materials, resonance acoustic materials and special-structure acoustic materials. Different materials have different sound absorption characteristics, such as the following:
(1) Resonant sound-absorbing materials (resonant sound-absorbing structures), which are divided into single resonators, compliant materials, perforated sound absorption, and micro-perforated plate sound absorption. Due to the poor low-frequency sound absorption performance of porous materials, in order to solve the problem of low-frequency sound absorption, resonance sound absorption structures are often used. Among the resonant sound-absorbing material structures, only the micro-perforated plate structure has the tendency of wide-band sound absorption, which can slightly make up for the shortcoming of the narrow resonance sound-absorbing frequency band.
(2) Porous sound-absorbing material: Porous sound-absorbing material has a large number of pores and continuous bubbles, the pores are interconnected, and the pores are deep inside the material, which has high sound absorption characteristics. Through the sound absorption structure composed of porous materials, the sound absorption performance of high frequency is usually better than that of low frequency, which expands the effective sound absorption frequency range.
(3) Special structure sound-absorbing material: the sound-absorbing wedge is a special sound-absorbing structure used in the anechoic chamber. The use of the sound-absorbing wedge can greatly reduce the size of the material compared with the use of porous materials; for some halls that require multi-functional use , such as multi-function halls, recording studios, studios, concert halls, etc. In order to adapt to different reverberation times and adjust the sound absorption, it is required that the indoor sound absorption conditions can be adjusted, which requires the use of adjustable sound absorption structures; space sound absorption A body is a sound-absorbing structure specially made for sound-absorbing purposes suspended in an interior space.
No.2 Research progress in the application of acoustic materials
In the past ten years, due to the unremitting efforts of the majority of scientific and technological workers, the research and application of low-frequency acoustic materials have made great progress. , attracting more and more attention.
In the review of the properties of melamine foam, it is introduced that melamine foam is a new type of foam with a three-dimensional grid structure with high open cell rate, and has excellent low-frequency sound absorption, flame retardancy, thermal insulation properties, heat and humidity resistance stability, hygienic safety and good secondary processing performance. These characteristics make the product have a wide range of applications (such as building materials, transportation, aviation, electronic information, household appliances), and also has a broad market prospect. Melamine foam has good sound absorption performance, especially the sound absorption coefficient of medium and high frequency (≥1kHz) is significantly higher than that of glass wool, slag wool and polyurethane foam, while the low frequency sound absorption coefficient is higher than that of fiber sound absorbing materials such as glass wool and slag wool. Slightly lower, not much different from the low-frequency sound absorption coefficient of polyurethane foam. Density has little effect on the sound absorption coefficient of melamine foam; increasing the thickness of the material can improve the sound absorption coefficient of the material at low frequency (<1kHz).
Due to the material characteristics of melamine foam, such as sound absorption, low density, high weight, soft texture, elasticity, heat insulation, water resistance and heat resistance, large temperature range and good interior decoration effect, it is suitable for indoor sound quality and sound environment in buildings. It has a wide range of applications in the improvement of mechanical equipment, especially in the noise reduction of transportation vehicles.
The damping performance of PVC/PNBR rubber-plastic alloy has a strong impact on the sound absorption performance of medium and low frequency noise, especially when the noise frequency is 250, 1000, 2000 Hz, the damping performance and the material’s sound absorption performance for medium and low frequency noise. There is an obvious dependence relationship, and it is expected to achieve the purpose of improving the sound absorption performance of the material to medium and low frequency noise by changing the damping performance of the material.
For the modification of the melamine foam, because the amino activity of melamine is relatively high, the two H atoms on the amino group are prone to electrophilic substitution reaction, so a linear structure modifier can be used to partially replace the H on the melamine amino group. This also puts forward a new idea for the modification of melamine resin.
Development Trends and Recommendations
As an intrinsic high-performance flame-retardant sound-absorbing foam, melamine foam has many characteristics that other additive flame-retardant foams do not have. The price advantage has broad application prospects in many fields. Countries around the world attach great importance to the development and research of this foam material, and have invested a lot of manpower, material and financial resources to conduct in-depth research on its preparation process and application, and conduct product development. The development trend of melamine foam application research mainly includes:
(1) use melamine foam materials that are easy to degrade and reuse;
(2) use new composite reinforced nanomaterials with good comprehensive properties,
(3) further expand the application field of melamine foam.
Melamine foam is a new type of foam that does not need to add flame retardants. In terms of application research, future work may focus on:
(1) The application of melamine resin that is stable in storage and use;
(2) The application of chemically modified melamine resin;
(3) Use melamine resin with good comprehensive properties to manufacture sound-absorbing material products that meet the requirements.
In addition, the majority of scientific and technological workers are also studying other new acoustic materials, such as non-woven acoustic materials for road sound barriers; carpet backing latex; sound-absorbing polyurethane foam; foam metal electrode materials and porous acoustic materials. The application fields of low-frequency acoustic materials will become more and more extensive.
Epilogue
To sum up, the use of resonant sound-absorbing structures can improve the low-frequency sound-absorbing properties of materials, but we can know from the close relationship between molecular structure and performance that if we can improve the sound-absorbing properties of materials from the molecular modification of the material body, The use of molecular structure materials with large steric hindrance to improve the internal friction of the material can improve the sound absorption performance of the material, so that the thinner material can achieve the effect of low frequency sound absorption, which is conducive to expanding the practical application field of the material. For the construction of a better living environment services.
Building spaces such as office lobbies, public canteens, classrooms, open offices, conference rooms, etc. are easily disturbed by various noises: the sounds of conversations, telephones, office equipment, etc. are continuously superimposed, forming continuous and disturbing noise pollution. . Long-term exposure to a high-noise environment often leads to difficulty in concentration, stress and fatigue, affects work efficiency and physical and mental health, and significantly reduces customer experience, comfort and satisfaction.
In response to this phenomenon, FoamTech, based on years of acoustic technology research and accumulation of experience, has successfully integrated acoustic design with artistic paintings to beautify the home, improve the acoustic environment, and make the sound system perform better. Art acoustic products and solution.
The melamine foam developed by FoamTech has significant sound absorption and noise reduction function, which can greatly improve the quality and comfort of the indoor sound environment of buildings; unique artistic taste and decorative effect can beautify the interior space of buildings; it can be cleaned and replaced from time to time, which increases the flexibility of use Sexual and decorative; it can be customized in combination with customer’s product and service posters, so as to play the value of marketing promotion.