RU2019132369A - SOUND ABSORPTION METHOD WITH RESONANCE INSERTS - Google Patents

Claims (15)

1. The method of sound absorption with resonant inserts, which consists in the fact that between the smooth and perforated surfaces of the sound-absorbing element, there is a layer of sound-absorbing material of complex shape, the layer of complex shape is made in the form of alternating solid sections and hollow sections, and the hollow sections are made in the form of prismatic surfaces, having a parallelogram in cross-section, and the inner surfaces are made in the form of a toothed structure, with the tops of the teeth facing inward of the prismatic surfaces, and the edges of the prismatic surfaces are fixed, respectively, on smooth and perforated surfaces, and the cavities of the hollow sections formed by the prismatic surfaces are filled with a sound absorber, and between with a smooth surface and continuous sections of a layer of sound-absorbing material of a complex shape, as well as between the perforated surface and solid sections, resonance plates with resonant inserts are placed tions of the necks of the "Helmholtz" resonators, characterized in that the resonance plate with resonant inserts, located between the perforated surface and the solid sections of the layer of sound-absorbing material of complex shape, is made of a box-shaped form, the upper surface of which adjoins the solid sections of the layer of sound-absorbing material, and the side edges are attached with corners to the perforated surface, while its lower surface, facing the perforated surface, is set in relation to it with a gap necessary to accommodate the resonant inserts that function as the necks of the "Helmholtz" resonators, and the parameters of the resonant inserts are calculated from the following dependencies: the maximum energy absorption for a single resonator will be observed at the resonant frequency:

where k _p - the conductivity of the holes in the resonant inserts 12, 13, 14, connecting them to the resonant plate 9, which has an analogue of the resonator chamber with a volume of V _p (m ³ ); V _p is the volume of the resonator chamber (m ³ ); с - speed of sound in air, assuming in calculations equal to 340 m / sec.

where n is the number of holes in the insert; S ₀ - the area of one hole with a diameter of do, m ² ; l hole - hole depth, m; given the volume Vp of the resonator cavity, according to the overall dimensions of the resonant plate 9, as well as the resonant frequency f _{p of the} "blade" impulse noise source, for example a fan, we determine the conductivity of the holes:

and the efficiency of noise reduction by this muffler will be determined by the formula:

where F is the cross-sectional area of the resonant plate 9, m ² ; f, f _p - exciting and natural frequencies of the Helmholtz resonator, while polyester is used as a sound-absorbing material, or a porous fibrous or foamy sound-absorbing material is used as a sound-absorbing material, which is made on the basis of basalt or glass fibers, or open-cell polyurethane foam with a protective sound-transparent shell made of thin glass cloth or aluminized lavsan film, or a porous sound-absorbing ceramic material is used as a sound-absorbing material, having a bulk density of 500 ÷ 1000 kg / m ³ , and consisting of 100 mass parts of pearlite with a particle diameter of 0.5 ÷ 2.0 mm, 100 ÷ 200 mass parts of one or more sintering materials and 10 ÷ 20 mass parts of binding materials. 2. The method of sound absorption with resonant inserts according to claim 1, characterized in that in the cavities of the hollow sections formed by prismatic surfaces having a toothed structure, spherical resonant elements with resonant inserts are arranged, which function as the necks of the "Helmholtz" resonators. 3. A method of sound absorption with resonant inserts according to claim 1, characterized in that for the analysis of comparative characteristics of sound absorption, a sound-absorbing structure made in the form of rigid and perforated walls is used, between which there is a multilayer sound-absorbing element made in the form of five layers, two of which, adjacent to the walls are sound-absorbing layers of materials of different densities, and the three central layers are combined, and the axial layer is made sound-absorbing, and the two symmetrically located adjacent layers are made of sound-reflecting material of a complex profile, consisting of uniformly distributed hollow tetrahedrons, allowing to reflect falling sound waves in all directions, each of the perforated walls has the following perforation parameters: hole diameter - 3 ÷ 7 mm, perforation percentage 10% ÷ 15%, and the hole shape can be made in the form of round, triangular, square holes, rectangular or diamond-shaped profile, while in the case of non-circular holes, the maximum diameter of the circle inscribed in the polygon should be considered as the nominal diameter, and rockwool basalt-based mineral wool slabs, or URSA-type mineral wool, are used as sound-absorbing material, or basalt wool of the P-75 type, or glass wool lined with fiberglass, and the sound-absorbing element is lined with an acoustically transparent material over its entire surface, for example, with EZ-100 fiberglass or with a polymer of the "visible" type, a porous noise-absorbing material, for example, foam aluminum or cermet or shell rock with a degree of porosity in the range of optimal values: 30 ÷ 45%, or metal foam, or a material in the form of compressed crumb made of hard vibration-damping materials, such as elastomer, polyurethane, or plastic compound such as "Agate", "Antivibrit" , "Shvim", pr The size of crumb fractions lies in the optimal range of values: 0.3 ... 2.5 mm, and porous mineral piece materials can also be used, for example pumice, vermiculite, kaolin, slags with cement or other binder, or synthetic fibers, while the surface fibrous sound absorbers are treated with special porous paints that allow air to pass through, for example, of the Acutex T type or covered with breathable fabrics or non-woven materials, for example Lutrasil; a material based on aluminum-containing alloys is used as a sound-reflecting material, followed by filling them with titanium hydride or air with a density within 0, 5 ... 0.9 kg / m ³ with the following strength properties: compressive strength within 5 ... 10 MPa, flexural strength within 10 ... 20 MPa, for example, foam aluminum, or soundproof plates based on glass staple fiber of the "Shumostop" type with material density equal to 60 ÷ 80 kg / m ³ , while adjacent to the made sound-absorbing m, the axial layer, two symmetrically located layers made of a sound-reflecting material of a complex profile, consisting of evenly distributed hollow tetrahedrons, allowing to reflect sound waves incident in all directions, are made with perforations.