RU2020107590A - SOUND ABSORPTION METHOD WITH RESONANCE INSERTS - Google Patents

Claims (13)

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 in section, the shape of a parallelogram, 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 the smooth surface and solid sections of a layer of sound-absorbing material of complex shape, as well as between the perforated surface and solid sections, resonance plates with resonant inserts are placed, which perform the functions throats of Helmholtz resonators, characterized in that the resonant 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-like shape, the upper surface of which adjoins the solid sections of the layer of sound-absorbing material, and the side faces are attached with corners to the perforated surface , while its lower surface, facing the side of the perforated surface, is set in relation to it with a gap necessary to accommodate resonant inserts that perform the functions of the necks of 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 ); s is the speed of sound in air, taking in calculations equal to 340 m / s

where n is the number of holes in the insert; S _o - the area of one hole with a diameter of do, m ² ; l _{of holes} - 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 binder materials, while in the cavities of hollow sections formed by prismatic surfaces having a toothed structure, spherical resonant elements with resonant inserts are placed n Helmholtz resonators.