The concept of "sound absorption" and "sound insulation" is often confused. Their diversity of structural features and purpose, they have great practical significance. One of the most harmful and dangerous impacts on people on the premises, is the noise generated by sources outside the building is within him. It is noise from industrial plants, the sounds of transport, machinery and utilities, etc. Internal noise in the building due to processes of human activity, as well as the work of building automation systems (elevators, plumbing and ventilation installations of heating, etc.) are two fundamentally different processes: absorption and sound insulation - is inextricably associated with a reduction of sound transmission in designs. If the sound source and receiver are in one room, the sound attenuation is due to the absorption of its enclosing structures or facilities with special devices, wall and ceiling materials with high structural porosity. Loss of energy of sound waves incident on the fence, in this case, due to the transition of the sound energy into other energy forms, mainly heat (sound absorption). If the source and receiver are in different rooms and shared walls, partitions or other structural elements of sound attenuation achieved by the properties of these barriers prevent the propagation of sound through these barriers (sound). Very often, both of these processes occur simultaneously: falling on the building envelope sound waves are partially reflected, returning to the sound source, partially absorbed, transformed into heat, partially pass through the barrier. All materials are designed to protect against noise in buildings that have common characteristics and classification differ in structure, elastic-plastic properties, flammability and shape. One of the specific, but fundamentally important characteristics of such materials is their purpose, according to which they are divided on the sound-absorbing and soundproofing. Call such a sound-absorbing material in which the solid occupies only part of the total. In this case, solid particles are relatively evenly distributed throughout the volume, creating numerous microscopic cavities interconnected. Vibrations of air caused by the effect of sound pressure at the surface of the material covered in these cavities with damping, which is due to the viscosity of air in the vapor and friction with the surface of pore walls. On structural features sound-absorbing materials are divided into fibrous and porous. Fibrous material is a set of parallel layers with a chaotic interlacing of fibers derived spunbond-blast method from molten rock, such as quartz, basalt, dolomite, as well as from molten glass. Of fiber mat produced products: mats, rolls, webs of varying thickness and semi-rigid or rigid plates, made from the same pulp with a small amount of binder and subsequent compaction. In a porous material substance is distributed in the form of solid grains or granules, forming a granular or cellular structure. Rigid porous materials, the structure dominated by intergranular porosity, made from gypsum, slag, perlite. Flexible foam made of polyester, have a cellular structure, in which the pore walls are flexible polymeric films. These materials include polyethylene foam, rubber and penopolipropileny. Fluctuations of these films cause additional losses of sound energy in the medium. Common feature for those and other absorbent materials is the presence of cross-cutting (communicating), then, through which pass relatively freely in the air flow. The main purpose of sound-deadening materials - to ensure, in indoor public places and industrial buildings (auditoriums, classrooms, sports and conference rooms, offices, agencies, stations, airports and other places of residence of a large number of people) of the optimal acoustic conditions due to an increase in their fund absorption. In this case, a fund absorption understand the product key performance indicators sound-absorbing material on the surface area of ??building envelope in which it appears. Indicator acoustic performance sound-absorbing materials - sound absorption coefficient (EWC) - a measure of an employee to assess the absorption properties of materials, unrecognized by the ratio of sound energy to the total sound energy incident on this surface. When total reflection of sound enclosures EWC is zero, and with the full-absorption unit. EWC material depends on the frequency of the incident sound, the thickness of the material and the angle of incidence of sound waves on the surface of the material. Distinguish normal EWC (at normal incidence of sound waves on the surface of the material) and reverberant bullpen defined a fall acoustic waves on the material from all sides and under all sorts of angles. Reverberant EWC is usually used in practical calculations. Both of these factors are frequency-dependent, ie in different areas of the sound frequency range, they take different values. Efficiency of sound absorption materials due to the presence of a large number of small open through pores with a large specific surface area. Using various types of raw materials and technological modes of production, create materials with specific structural characteristics - minimum density, high porosity, the maximum specific pore surface and, consequently, with the highest rates of sound-absorbing properties. Soft absorbent material is made on the basis of mineral wool or fiberglass with a minimum amount of binder or without him. These include mats or roller blade, which are usually used in combination with protective perforated sheet screens (made of aluminum, gypsum board, coated with a thin porous film. EWC these materials at medium frequencies reaches 0,7-0,85. By the semi-rigid materials include Mineral wool and glass-plate thickness from 12 to 50 mm, a density of 40-130 kg / cubic meter. for the content of the binder to 15% by weight. The surface of the plates covered with a porous paint with glass or plastic film. EWC these materials in the mid range - 0,75 -1.0. Semi-sound-absorbing materials are also considered basalt absorbent mats are produced from very thin basalt fiber coated with fiberglass. Their density in more than 25kg/m.kub. and the EWC in the mid range - more than 0.9. Unlike sound-absorbing materials the main indicators of acoustic performance soundproof (cushioning) materials are considered dynamic elastic modulus E, the coefficient of relative compression and the rate of energy loss fluctuations due to internal friction in the material during its deformation. Since all the materials in most cases are designed to isolate the waves generated by shocks and mechanical structural vibrations (shock and structural noise) and travel considerable distances to building structures, the presence or absence of through porosity in the structure of such material does not play a decisive role in assessing the acoustic performance. To soundproof materials are primarily the same fiber boards and mats on the synthetic binding agent of mineral or glass fiber and porous, soft rubber, modern flexible plastic polyethylene foam, rubber and polypropylene .. Effectiveness of an elastic strip is determined, basically, the elastic modulus of the material from which it is made, as well as its thickness and density . Since most sound-proof gasket materials are not perfectly elastic bodies, when exposed to periodic external force, laying its deformation is not time to develop during the period the impact strength and elastic modulus E becomes a complex quantity. The real part of the module, which characterizes the energy produced by unit volume and give the body for the period and is called the dynamic modulus of elasticity. The imaginary part of the elastic modulus E, called the module power losses. It characterizes that part of the energy irreversibly dissipated during deformation. The effectiveness of insulation elastic cushioning layer depends not only on the elastic modulus E, but also on thickness of the outer layer in compressed state. Therefore, when choosing a sound-proofing material is important to pay attention to the values ??of the coefficients of the relative compression of the material as soundproofing layer under stress. Since the calculation of the expected improvement of sound insulation thicknesses used soundproof layer in compressed state. Depending on the structure , method of manufacture and the type of feedstock values ??of dynamic modulus of elasticity E sound insulation materials should be in the range 105 ... 108 Pa at a load on the sound insulation layer 2000 Pa, the loss factor must have a value of not less than 0.05. In most cases the most efficient elastic layers of sound insulation materials used when constructing the so-called floating floor (tie) for improved sound insulation and overlap in part, to improve airborne sound insulation. For this purpose, ties made of concrete, plaster, asphalt and other similar materials make the thickness of 30-50 mm, thickness of the elastic layer 6 - 15 mm. Typically, the elastic layer is used the most common and relatively inexpensive foamed polymer. These materials are more effective than mineral wool pads and more cheaply than natural materials such as cork, as have a number of surprisingly high thermal and acoustic insulation properties. on construction sites they are used not only as a sound-proof seals in the construction of a floating floor, but also for facing multiple pipelines, air ducts and channels, which may spread and transmission of noise from its source to be protected. a specific role for such materials to prevent the spread of so-called structurally sound , largely in the effectiveness of sound insulation in buildings, modern buildings of reinforced concrete. We hope that this brief excursion into the building acoustics will help you understand a wide range of proposed materials for insulation and sound absorption.
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