ACOUSTIC CEILING FOR VEHICLES Russian patent published in 2018 - IPC E04B9/00 E04B1/84 

FIELD: acoustics.

SUBSTANCE: invention relates to acoustics, in particular to means for reduction for vehicles. Acoustic ceiling for vehicles consists of a rigid frame suspended from the ceiling of the vehicle with a sound-absorbing structure inside the frame, wrapped in an acoustically transparent material. Perforated sheet is attached to the frame. Frame is made in the form of a rectangular parallelepiped with the dimensions of the sides in terms of a×b, the ratio of which lies in the optimal range of values of a:b=1:1–2:1, as well as with the optimal ratio of sizes c:d=0.1–0.5. Frame elements are attached to each other by means of brackets rigidly connected to rod, which are connected to suspensions. Perforated sheet has the following perforation parameters: perforation diameter – 3–7 mm, perforation percentage 10–15 %. Lamps are mounted in frame. Fastening the frame to the ceiling of the vehicle is performed by using dowel-screws. Sound-absorbing structure contains smooth and perforated surfaces, between which there is a multi-layer sound-absorbing structure in the form of rigid and perforated walls, between which there are two layers: a sound-reflecting layer, adjacent to the rigid wall, and a sound-absorbing layer adjacent to the perforated wall. Shape of the hole in the perforated wall can be made in the form of holes round, triangular, square, rectangular or diamond-shaped profile, at that, in case of non-circular holes, as the conditional diameter the inscribed in the polygon circle maximum diameter should be considered. Mineral wool on a basalt basis is used as a sound-absorbing material, or mineral wool, or basalt wool, or glass wool with a glass fiber cladding, or foamed polymer, the fibrous sound absorbers surface is treated with special air permeable porous paints, or is covered with air permeable fabrics or non-woven materials. 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 in the range of 0.5–0.9 kg/m³ with the following strength properties: compressive strength in the range of 5–10 MPa, flexural strength in the range of 10–20 MPa, for example, foam aluminum, or sound-proof plates based on Shumostop glass staple fiber with a material density of 60÷80 kg/m³. Sound-reflecting layer is made with perforations of sound-reflecting material of a complex profile consisting of uniformly distributed hollow tetrahedra, which allow reflecting sound waves falling in all directions. In this case, the perforation on the sound-reflecting layer is made by analogy of the throttle holes, which are the neck of the Helmholtz resonators, whose capacity is determined by the volume of the sound-reflecting layer and the rigid wall of the sound-absorbing element adjacent to it.

EFFECT: technical result consists in increasing the efficiency of noise attenuation by increasing the absorption surface and expanding the frequency range.

1 cl, 2 dwg