Sound proof materials refer to a kind of materials, components or structures that insulate, cut off and separate the noise transmitted in the air.For sound insulation materials, to reduce the transmission of sound energy and block the transmission of sound, they should not be porous, loose and breathable like sound absorption materials. On the contrary, their materials should be heavy and dense, such as steel plates, lead plates, brick walls and other materials.The sound insulation material shall be dense and free of pores or gaps;It has a large weight.Because this kind of sound insulation material is dense and difficult to absorb and transmit sound energy but has strong reflection energy, its sound absorption performance is poor.[1]
The number of decibels related to the incident sound energy on one side of the material and the transmitted sound energy on the other side is the sound insulation of the material, usually expressed by the symbol R (dB).Sound insulation materials or components will have different sound insulation effects due to different use occasions and test methods.The sound insulation material can attenuate the transmitted sound energy to 10-3~10-4 or less of the incident sound energy. For the convenience of expression, its sound insulation is measured in decibels.
Composition
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All materials that can be used to block noise are collectively referred to as sound insulation materials.Sound insulation materialThere are many kinds of bricks, reinforced concrete walls, wooden boardsplasterboard, iron plate, sound insulation felt, fiberboard, etc.Strictly speaking, almost all materials have sound insulation effect, and the difference is that the volume between different materials is different.The sound insulation of the same material varies greatly due to its different surface density.Sound insulation follows the principle of mass lawThat is, the greater the unit dense area density of the sound insulation material, the greater the sound insulation volume, and the area density is proportional to the sound insulation amount.
The airtight solid material has sound insulation effect for the sound waves propagating in the air. The sound insulation effect depends on the quality of the material per unit area.
A partition with a very large area has a mass per unit area of ms. When the sound wave is vertically incident from the left, the partition will be excited to vibrate as a whole, and this vibration will then radiate sound waves to the right space.In terms of unit area, the ratio of the sound energy transmitted to the right space to the sound energy incident on the interlayer is called the transmission coefficient τ.Define the transmission loss (also known as transmission loss) of infinite spacer material
：
(1)
In the above simple case, it can be calculated that the transmission loss is approximately:
(2)
Where ω=2 π f is the circular frequency, ρ 0 and c0 are the density of air and the speed of acoustic wave propagation.
The size of indicates the sound insulation capacity of the material.(2) An important feature of formula is that if the mass per unit area of material is doubled, the transmission loss will increase by 6db.The basic law of sound insulation is called "the law of mass", that is, sound insulation depends on weight.Therefore, materials with large mass per unit area, such as brick walls, cement walls or thick steel plates and lead plates, have good sound insulation effects.
(2) The formula also shows that the sound insulation of single layer is good at high frequency and poor at low frequency.Every time the frequency is doubled, the transmission loss increases by 6 db.
Note: transmission loss
It is the theoretical "sound insulation amount" when the partition area is infinite. As a stack of walls or floors, it has edges connected with other building components. At this time, the "sound insulation amount" is different from the transmission loss expressed in Formula (1).The sound insulation capacity is increased because the edge is close to fixed, and the vibration of the plate as the edge is fixed has a certain resonance frequency, which reduces the sound insulation effect at some resonance frequency points.As the partition or floor between two adjacent rooms, because there are multiple sound (or vibration) transmission channels between the two rooms, the sound insulation amount (only known as the sound level difference) between the two rooms cannot be represented by the transmission loss of the partition.
The sound insulation material is physically elastic to a certain extent. When the sound wave enters, it will stimulate the vibration to propagate in the insulation layer.When the sound wave is not vertically incident, but is incident at an angle θ with the barrier, the sound wave front reaches the surface of the barrier in turn, and the sound wave that first arrives at the barrier excites the flexural vibration wave in the barrier to propagate laterally along the barrier. If the propagation speed of the flexural wave is consistent with the traveling speed of the sound wave in the air that gradually reaches the surface of the barrier, the sound wave will strengthen the vibration of the flexural wave, which is called coincidence effect.At this time, the radiance of bending wave vibration is particularly large, and the energy of radiating sound waves to the air on the other side is also particularly large, thus reducing the sound insulation effect.The frequency fc producing coincidence effect is:
(3)
Where ρ, μ and e are the density, Poisson's ratio and Young's modulus of the interlayer material respectively, and h is the thickness of the interlayer.The arbitrary coincidence frequency fc is related to the incident angle θ of the acoustic wave.The sound field in most rooms is close to the reverberation sound field, and the incidence angle reaching the interlayer is possible from 0 ° to 90 °, so the coincidence frequency occurs in the
The initial frequency range, that is, the coincidence effect makes the sound insulation effect of a certain frequency range worse.Generally, this frequency range occurs in the middle and high frequencies.It is known from the mass law that the middle and high frequency sound insulation is large. Except for the metal plate with small internal damping, the phenomenon that the middle and high frequency sound insulation is reduced due to the coincidence effect will not cause much trouble.
Double layer sound insulation structure
According to the mass law, if the frequency is reduced by half, the transmission loss will be reduced by 6db;To improve the sound insulation effect, the mass is doubled and the transmission loss is increased by 6db.Under the rule of this law, if we want to significantly improve the sound insulation capacity, it is obviously not effective or even impossible to simply increase the quality of the partition, such as increasing the thickness of the wall, such as the sound insulation structure on the aircraft.At this time, the solution is mainly to use double-layer or even multi-layer sound insulation structure.
Double layer sound insulation structure, with the mass per unit area of m1 and m2, and the thickness of the middle air layer of l.The transmission loss of the double-layer structure can be calculated theoretically, and the results are relatively complex. Different simplified expressions can be obtained in different frequency ranges. Here, only qualitative introduction is made.
Two compartments and the middle air layer form a resonance system, and the resonance frequency is fr (the unit of m is kg/m2, and the unit of l is m):
(4)
Near this resonance frequency, the sound insulation effect is greatly reduced.However, for heavy walls, this frequency is lower than the audible frequency range.For example, m1 is a half brick wall of 250kg/m2, m2 is a brick wall of 500kg/m2, and the thickness of the air layer is 0?5 m, then the resonance frequency is about 7 hz.
For light structure double-layer sound insulation, the resonance frequency may fall within the audible frequency range, for example, the two aluminum plates are 5?2kg/m2 and 2?6kg/m2, the middle air layer is 5cm, and the resonance frequency can be calculated to be about 200hz.At this time, it should be filled between the two platesDamping materialTo suppress the vibration of the plate.Generally, if the steel plate is used as a double-layer sound insulation structure, the damping layer is coated on the steel plate to suppress the vibration of the steel plate.
Below the resonance frequency fr, the sound insulation effect of double layers is the same as that of a layer (m1+m2) without air layer;In the frequency range above fr, the double-layer sound insulation effect is close to the sum of the transmission losses of two single-layer sound insulation;At higher frequencies, when the thickness of the air layer l is an odd number of times of a quarter of the wavelength, the double-layer sound insulation effect is equivalent to the sum of the transmission losses of two single layers plus 6 db. When l is an even number of times of the wavelength, the double-layer sound insulation effect is equivalent to the transmission loss of two single layers together plus 6 db. At other frequencies, the transmission loss is between these two values.Therefore, in general, when the frequency is greater than fr, the double-layer sound insulation structure significantly improves the sound insulation efficiency.
Generally, two layers of double-layer sound insulation structure do not use the same material with the same thickness to avoid the sameCoincidence frequency。
In the design and construction, special attention shall be paid to that there shall be no rigid connection between the two floors.The double-layer structure of solid air solid is destroyed, and the two layers of solid partitions are connected by rigid members, so that the vibration of the two partitions is connected together, and the sound insulation is greatly reduced.Especially for double-layer light structure sound insulation, when they must be supported or connected with each other, they must be supported or suspended by elastic components. At the same time, it should be noted that there should be no seams or holes between the two spaces that need to be divided."Air leakage" means sound leakage, which is a practical problem of sound insulation.
Production process
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Through cutting, gluing, cutting, molding and other deep processing methods.Manufacture various specifications and irregular specifications to meet the needs of industrial manufacturers or other supporting enterprises such as hall decoration design, home appliance quality inspection, instrument testing, automobile molding, etc., and develop different specifications and models of sound insulation materials according to user needs. The sound insulation materials have the structural characteristics of compactness, weight, strong damping, high elasticity, water resistance, weather resistance, oil resistance, and flame retardancy.[2]
application area
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TV stations, cinemas, opera houses, concert halls, conference centers, gyms, sound rooms, homes, shopping malls, hotels, karaoke bars, lounges, restaurants, etc.
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General rules of sound insulation of building components
1. Law of mass
There is a general rule for sound insulation of partition walls, that is, the heavier the material (the greater the surface density, or the mass per unit area), the better the sound insulation effect.For single-layer dense and uniform wall, the sound insulation will increase by 6dB theoretically every time the area density is doubled, which is called the quality law.For double-layerPaper faced gypsum boardFor walls, the mass law plays an important role, that is, increasing the number of layers or thickness of the board can improve the sound insulation.Because the sound frequency vibration form of the keel double wall system is very complex, the embodiment of the mass law is more complex than that of a single wall.The sound insulation effect of single-layer gypsum plasterboard is very poor, for example, the standard sound insulation amount of 12mm thick gypsum plasterboard with a surface density of 10kg/m2 is Rw=29dB.In theory, Rw can only reach 41dB even if four layers of gypsum plasterboard are stacked together.Light homogeneous wall, such as gypsum blockAerated concrete slab, expanded perlite plate, light round orifice plate, etc., the surface density is mostly 60-100kg/m2, limited by the mass law, and the sound insulation amount Rw=35-40dB.For single-layer heavy walls, the surface density is more than 250kg/m2, such as 120 brick walls, 90 thick hollow concrete blocks, 100 thick concrete wallboards, etc., the sound insulation amount Rw can reach about 45dB, and the sound insulation amount of 240 brick walls and 200 thick concrete walls with the surface density more than 500kg/m2 can reach about 50-55dB.
2. Resonance frequency
Any partition has an inherent resonance frequency. When the frequency of acoustic wave is consistent with the resonance frequency of the wall, the whole wall will have resonance, and the sound insulation amount of this frequency will be greatly reduced.Generally, the thicker the wall is, the lower the resonance frequency is. When the resonance frequency is lower than the lowest reference frequency of sound insulation evaluation, 100Hz, the impact on the sound insulation amount Rw is greatly increased because the auditory characteristics of the human ear are very sensitive to low frequencies.For 12mm and 15mm thick two different surface densitiesPaper faced gypsum boardThere are different resonance frequencies.The surface density of 12mm paper faced gypsum board is 10kg/m2, and that of 15mm paper faced gypsum board is about 12kg/m2.The resonance frequency of the 15mm thick gypsum plasterboard wall is basically lower than the minimum frequency range of 100Hz, so the resonance frequency has little impact on the sound insulation performance of the 15mm thick gypsum plasterboard wall components.However, for the 12mm plate, the sound insulation performance near 100Hz has a great impact, resulting in the sound insulation at the low-frequency 100Hz, 125Hz and 200Hz is much lower than that of the 15mm plate, mainly because of the resonance frequency.
3. Anastomotic effect
After the acoustic wave contacts the wallboard, in addition to the forced vibration in the vertical direction, there is also the forced bending vibration along the board surface direction.At a certain frequency, the forced bending vibration will coincide with the natural free bending vibration of the plate. At this time, the plate will bend very obediently with the incident sound, resulting in a large amount of sound energy transmitted to the other side, forming a low valley of sound insulation. This phenomenon is called the coincidence effect, and this frequency is called the coincidence frequency fc.
Both theory and experiment show that the light, thin and flexible wall fc is high, and the coincidence effect is weak;Thick, heavy and rigid walls have low fc and strong coincidence effect.12mm、15mmPaper faced gypsum boardThe fc of is about 3.15KHz and 2KHz respectively.The sound insulation of the 12mm plate decreases at 3.15KHz, and the sound insulation of the 15mm plate decreases more seriously at 2KHz, even the downward trend is stronger than the law of mass, resulting in a much lower sound insulation at this frequency position than that of the 12mm plate.The coincidence frequency fc of the superposition of double layers of the same plate is basically the same as that of the single layer plate. Because of the vibration superposition of double layers, the coincidence effect is more intense, and the coincidence valley will become deeper.If plates with different thicknesses are used for lamination, the inosculating valleys will be staggered from each other, and each inosculating valley is shallow, which is beneficial to the sound insulation performance.The intense matching effect of the double-layer board is very obvious, which will cause the sound insulation of the partition with the double-layer 15mm board structure to be lower than that of the partition with the double-layer 12mm board at 3150Hz.The area density of the partition with one layer of 12mm and one layer of 15mm boards is lower than that of the double-layer 15mm partition, but the sound insulation will increase instead, which is the result of the weakening of the coincidence effect.
The factors of coincidence effect are complex, which are not only related to the surface density of the material, but also related to the elastic modulus, thickness, Poisson's ratio and other conditions of the material.
Paper faced gypsum boardThe foaming condition in the manufacturing process will affect these factors, including the most direct surface density.From a large number of experiments, we found that if the area density is reduced within a certain range, the coincidence frequency will become higher, and the coincidence effect will become weaker, which is beneficial to sound insulation.
There are light partition walls with large surface density and thickness, such asAerated concrete slab, gypsum blocks, etc., the coincidence frequency often occurs in the range of 250-2000Hz. The heavier and thicker the lightweight board, the deeper the "coincidence valley" appears in the low-frequency range of the sound insulation curve, which severely limits the sound insulation of the wallboard.Even if it is made into a double-layer wall with an air layer in the middle, the sound insulation is not high because of the superposition of the coincidence effect. For example, the double-layer 90 aerated concrete slab is 50 mm hollow, and the sound insulation amount can only reach about 48 dB, while the sound insulation amount of the double row keel six layer 12 mm gypsum board wall with the same weight can reach 60 dB, which is mainly because of the high coincidence frequency of 12 gypsum boards,The coincidence effect is not as strong as that of 90% aerated concrete slab.
4. Acoustic bridge
When the plate is directly fixed on the keel, the vibration of the plate on the side receiving the sound will be transmitted to the plate on the other side through the keel. This phenomenon of transmitting sound energy like a bridge is called sound bridge.The more sound bridges, the larger the contact area, and the stronger the rigid connection, the more serious the sound bridge phenomenon, and the worse the sound insulation effect.Add elastic pads between plates and keels, such as elastic metal strips or elastic material padsPaper faced gypsum boardThere is a certain amount of improvement in wall sound insulation, which can be increased by 3dB at most.In addition, the stiffness of the light steel keel itself is relatively small, and the sound bridge effect on the plates on both sides is better than that of the wooden keel and gypsum keel with rectangular section. The sound insulation effect of the light steel keel gypsum board partition is better than that of the wooden keel and gypsum keel partition with the same structure.
For light steel keel gypsum board wall, sometimes the keel structure is made into staggered structure and double-layer structure in order to reduce the sound bridge and obtain higher sound insulation.The staggered structure is that the vertical keels are staggered and separated, the plates on both sides are not fixed on one keel at the same time, and the heaven and earth keels share one set;The double-layer structure is that the heaven and earth keel and the vertical keel are made into two layers respectively, without any connection in the middle, and the plates are fixed on their respective keels.Theoretically, the sound insulation of staggered keel partition is better than that of ordinary keel partition, which can be increased by 1-3dB;The sound insulation of double-layer keel partition is better than staggered keel partition, which can be 7-8dB higher than ordinary keel partition.The increased sound insulation is due to the weakened sound bridge.
5. Slab joints and holes
If there are gaps and holes on the partition, the sound insulation of the partition will be greatly reduced.If the sound insulation of the partition wall itself reaches 50dB, and there are 1/10000 gaps and holes on the wall, the comprehensive sound insulation will be reduced to 40dB.In order to prevent the gap between the gypsum board wall and the original structure, plastic elastic adhesive strips are usually padded when installing keels around the wall.In addition, when there are two layers of gypsum boards on each side, they should be installed in staggered joints. The inner layer can not be pointed, but only the outer layer, which has little impact on the sound insulation of the partition.However, one layer of board on each side must be pointed, otherwise the sound insulation will decrease by 12-17dB.
Difference between sound insulation material and sound absorption material
At present, noise has become a major environmental pollution, and the acoustic environment of buildings has attracted more and more attention.It is one of the most common and basic technical measures in building noise control engineering to select appropriate materials for sound absorption and insulation treatment of buildings.
Due to the lack of understanding of the means of noise control, "sound absorption" and "sound insulation", as completely different concepts, are often confused.Glass wool, rock mineral wool and other materials with good sound absorption but poor sound insulation performance are mistakenly called "sound insulation materials"Plant fibreThe sound absorption board made of raw materials is named "sound insulation board" and used to solve the sound insulation problem of buildings.In order to reasonably use materials and improve the noise control effect of buildings, it is necessary to further understand and clarify the concepts of "sound absorption" and "sound insulation".
The difference between sound absorption and sound insulation of materials is that,Sound absorption of materialsFocusing on the size of the reflected sound energy on the side of the sound source, the goal is to reduce the reflected sound energy.The attenuation and absorption of the sound absorbing material to the incident sound energy is generally only a few tenths, so its sound absorption capacity, that is, the sound absorption coefficient, can be expressed in decimal numbers;Material sound insulationFocusing on the size of the transmitted sound energy on the other side of the incident sound source, the goal is to reduce the transmitted sound energy.
The two materialsdifferenceYes:
The reflection of the sound absorbing material on the incident sound energy is very small, which means that the sound energy can easily enter and pass through this material;The material should be porous, loose and breathable, which is typicalPorous sound-absorbing material, onTechnicallyIt is usually in the form of fiber, granule orFoaming materialTo form a porous structure;structure characteristicsYes: The material has a large number of interconnected micropores from the surface to the inside, that is, it has certain permeability.When sound waves incident onporous material On the surface, it causes the air vibration in the micropores. Due to the friction resistance, the viscous resistance of the air and the heat conduction, a considerable part of the sound energy is converted into heat energy, thus playing the role of sound absorption.
Sound insulation materials can not be as porous, loose and breathable as sound absorption materials to reduce the transmission of sound energy and block the transmission of sound. On the contrary, their materials should be heavy and dense, such as steel plate, lead plate, brick wall and other materials.The sound insulation material shall be dense and free of pores or gaps;It has a large weight.Because this kind of sound insulation material is dense and difficult to absorb and transmit sound energy but has strong reflection energy, its sound absorption performance is poor.
In engineering, sound absorption treatment and sound insulation treatment have different goals and emphases. The goal of sound absorption treatment is to reduce the repeated reflection of sound in the room, that is, to reduce the reverberation in the room, and to shorten the duration of reverberation, that is, the reverberation time;In the case of continuous noise, this reduction is reflected in the reduction of indoor noise level, which is for the sound source and sound absorption materials to be located in the same building space.The sound absorption materials also absorb the sound from adjacent rooms, which is equivalent to improving the sound insulation of the enclosure structure.
Sound insulation treatment focuses on isolating the transmission of noise from the sound source room to the adjacent room, so as to prevent the adjacent room from noise interference.
It can be seen that the noise reduction effect of sound insulation materials or sound insulation structures is much higher than that of sound absorption materials.This indicates that when the noise source in a room can be separated, sound insulation measures should be taken first;Sound absorption measures shall be taken only when the sound source cannot be isolated and the indoor noise needs to be reduced.
The special function of sound absorption materials is more reflected 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 reverberation time of the large building space is long, which affects the indoor hearing conditions. At this time, it is often inseparable from the adjustment of the reverberation time by the sound absorption materials.For large halls such as cinemas, auditoriums and concert halls, appropriate sound absorption materials can be selected according to their different listening requirements, and the reverberation time can be adjusted in combination with the shape to meet the requirements of different subjective feelings such as clear and full listening.From this point of view, sound absorption material shows its unique importance, so the acoustic material usually refers to sound absorption material.
Sound absorption and sound insulation are essentially different, but in specific engineering applications, they are often combined and play a comprehensive noise reduction effect.Theoretically, increasing the indoor sound absorption is equivalent to improving the sound insulation of partition walls.The common ones are sound insulation rooms, sound insulation covers, composite wallboards composed of plates, sound insulation barriers on main roads, sound insulation screens in workshops, pipe wrapping, etc.
If used alone, sound absorbing materials can absorb and reduce the noise in the room where the sound source is located, but they cannot effectively isolate the noise from the outside.When sound absorption materials and sound insulation materials are used together, or when sound absorption materials are used as a part of sound insulation structure, the beneficial result is generally shown as the improvement of sound insulation capacity of sound insulation structure.
Building partition materials and sound insulation components
In order to reasonably select materials and improve the effect of sound absorption and insulation treatment of buildings, it should be the primary basic problem in building noise control to distinguish sound absorption, sound insulation, sound absorption materials and sound insulation materials from each other.
For buildings built in most countries in the 1980s and before, most of the partitions are made of clay bricks. The sound insulation capacity of 240 mm clay brick walls is above 50 dB, and the sound insulation effect is good.But today's building partitions have undergone fundamental changes. On the one hand, in order to meet the needs of environmental protection, the use of clay bricks in buildings has been prohibited, because the production of clay bricks will damage farmland;On the other hand, because the new building system and high-rise buildings require light weight, the partition structure tends to be thin.Light wallThe sound insulation amount of is generally low, and the single-layer wall is generally less than 50dB. It is usually below 45dB, which makes the sound insulation effect worse than the traditional clay brick wall.
There are five main categories of partition materials and components commonly used at present[3]Their sound insulation conditions are generally as follows:
(1) Concrete wall
The sound insulation of cast-in-place solid reinforced concrete wall with a thickness of more than 200 mm is close to that of 240 mm clay brick wall. The sound insulation of concrete wall with a thickness of 150~180 mm is about 47~48 dB, but the sound insulation of reinforced concrete perforated plate with a surface density of 200 kg/m2 is less than 45 dB
(2) Block wall
There are many kinds of blocks, including load-bearing and non load-bearing blocks according to their functions.Common blocks mainly include hollow and solid concrete blocks such as ceramsite, fly ash, slag, sand and gravel;Gypsum, calcium silicate and other blocks.
The sound insulation of block wall varies with the weight and thickness of the wall.The sound insulation performance of load-bearing block walls with similar surface density to clay brick walls is also similar to that of clay brick wallscement mortarThe sound insulation performance of plastered lightweight block filled partition wall depends to a large extent on the thickness of the plastering layer on the wall surface. The sound insulation amount of 15mm-20mm thick cement mortar plastered on both sides is about 43-48dB, and the sound insulation amount of lightweight block wall with surface density less than 80kg/m2 is usually below 40dB
(3) Slat wall
The batten for building partition wall is generally 60mm~120mm thick, and the surface density is generally less than 80kg/m2, which has the advantages of light weight and convenient construction
The slat wall can be further divided into two categories:Inorganic cementitious materialSolid or perforated slats made with aggregates, such as (reinforced)Lightweight aggregate concreteSlabs, autoclaved aerated concrete slats, steel mesh ceramsite concrete slats, gypsum slats, etc. The sound insulation of such single-layer lightweight slat walls is generally between 32 and 40dB;The other type is prefabricated sandwich panels pre compounded by dense surface materials and light core materials in the factory, such as concrete rock wool or polystyrene sandwich panels, fiber cement lightweight sandwich panels, etc.The sound insulation of prefabricated sandwich panel walls is generally between 35 and 44 dB
(4) . Sheet composite wall
The thin plate composite wall is formed by fixing the thin plate on both sides of the keel at the construction siteLight wall。The thickness of the thin plate is generally 6mm~12mm. The thin plate is used as the wall face laminate, and rock wool or glass wool is filled between the wall keels.Sheet varieties includePaper faced gypsum board、Fiber gypsum board、Fiber cement board, calcium silicate board, calcium magnesium board, etc
The sound insulation of the thin plate itself is not high, and the sound insulation of the single layer plate is between 26 and 30dBLightgage Steel JoistThe double-layer hollow cotton filled composite wall composed of rock wool, rock wool (or glass wool) can achieve good sound insulation effect. Their sound insulation capacity is usually 40~49dB. The sound insulation capacity of the wall can be greater than 50dB by increasing the number of thin layers
(5) . Field sprayingcement mortarCore board wall of surface course
This kind of partition is sprayed with cement mortar on both sides of the core plate after the finished core plate is installed on the construction site.Common core material plates include steel wire mesh polystyrene plate, steel wire mesh rock wool plate, and plastic hollow internal formwork.
The sound insulation of such walls is related to the type of core material and the thickness of cement mortar surface layer, and their sound insulation is generally between 35 and 42 dB
To sum up, at present, a considerable number of lightweight partitions at home and abroad have poor sound insulation performance. The sound insulation capacity of single layer walls cannot meet the minimum sound insulation requirements of residential household walls, and can only be used for interior partitions.In order to improve the sound insulation of lightweight partitions, architectural acoustics workers at home and abroad have carried out a lot of research work and accumulated some experience.The following are some basic characteristics and rules of sound insulation of wallboard:
1. Sound insulation varies with different materials
The sound insulation amount of single-layer uniform dense wallboard obeys the "sound insulation quality law" of architectural acoustics, that is, the sound insulation amount is proportional to the weight of the unit area of the component, and the sound insulation amount increases by about 4~5dB every time the area density is doubled. When the sound wave is projected on the wallboard, the heavy wall is less likely to excite vibration than the light wall, and the low frequency is easier to excite vibration than the high frequency. Therefore, the sound insulation of the heavy wall is better than that of the light wall,High frequency is better than low frequency for sound insulation
The surface density of light partition walls is limited. To improve their sound insulation, double-layer or multi-layer composite structures should be used
2. Setting of air layer
The double wall structure is adopted, and a certain air layer gap is left between the two walls. Because of the elastic layer of the air layer, the total sound insulation of the wall can exceed the mass law
3. Application of sound absorbing materials
Placing sound absorption materials in the air layer of the double wall will further improve the sound insulation of the double wall. The greater the thickness of the sound absorption materials, the better the sound absorption performance of the sound absorption materials, the more significant the improvement of the sound insulation
The sound absorption material placed in the air layer of the double wall is more effective for the light double wall than for the heavy double wall
4. Attention should be paid to the appearance of sound bridge
The rigid connection of solid sound bridge between the air layers of the double wall shall be avoided as far as possible. If there is sound bridge, the elastic layer of the air layer will be destroyed and the sound insulation will be reduced
The hollow part of the hollow slab partition or the hollow block partition can reduce the weight of the wall, but it is not good for sound insulation. For building components such as hollow slabs and hollow blocks and the built hollow bucket walls, their internal cavities cannot be mistaken for the air layer that can play the role of sound insulation, because the surrounding of these cavities is a 100% rigid connection sound bridge,It does not play the elastic role of the air layer at all. Compared with the solid plate, the sound insulation of the hollow plate of the same material will be lower or approximately equal to the sound insulation of the solid plate when the surface density is the same
5. The plastering layer can increase the sound insulation
Holes and gaps have a great adverse impact on sound insulation. Small holes and gaps on the wall will reduce high-frequency sound insulation. With the increase of holes or gaps, high-frequency sound insulation will gradually decrease, and the impact will expand to the middle and low frequencies
For some light aggregate hollow block walls, since there are a large number of interconnected holes and small joints in the block materials, the wall surface must be plastered (sealed) after the completion of block masonry, otherwise the sound insulation is very low. For example, a 190mm thickCeramsite hollow blockFor the masonry wall, the sound insulation is less than 20dB when the surface is not plastered. When the thickness of the plastering layer is increased to 30mm, the sound insulation of the wall will reach 50dB
6. Plates made of different materials can avoid "fit" phenomenon
When the wallboard is excited by sound waves for bending vibration, the coincidence effect will occur at a certain frequency band, forming a sound insulation trough. The coincidence frequency is not only related to the stiffness and surface density of the wallboard, but also moves down with the increase of the thickness of the board
For the wall panels on both sides of the double-layer thin composite wall, two panels with different thicknesses or materials are selected to prevent the coincidence of the two panels at the same time, so that the coincidence valleys of the two panels are staggered, thus improving the sound insulation performance of the wall
Sound absorption, for the same space, changes the characteristics of the indoor sound field.The main function of sound absorption is to absorb the reverberation in the room, which has no effect on the direct sound, that is to say, sound absorption can improve the sound quality, but has poor effect on noise reduction;The sound absorbing material is porous and evacuated, and the sound insulation is mainly dense;
Sound insulation is relative to two spaces. The main function of sound insulation is to cut off sound from one space to another and prevent noise interference.The specific requirements of sound insulation materials are: dense, without pores, and with large weight
However, noise reduction is generally handled by combining sound absorption and insulation, that is, sound insulation is used to isolate external noise and indoor noise from the outside, and then sound absorption is used to mediate indoor reverberation. The sound insulation of building enclosure structures, such as walls, doors, windows, floors and roofs, directly involves the introduction of outdoor traffic, construction, neighborhood living noise, and factory production equipment noiseThe outward spread of high noise in the machine room, discotheque and other rooms will affect the surrounding environment.Therefore, building sound insulation materials are the technical guarantee for obtaining quiet acoustic environment, and low indoor environmental noise is also the basic condition for good indoor sound quality
Sound insulation is to reduce the sound pressure level from the source to the destination. From the perspective of activity, sound insulation measures can be divided into active and passive;But the passive method is often used - even if the sound energy is converted into another form of energy consumption.
