# US 11,929,053 B2 · Broadband sound absorber based on inhomogeneous-distributed Helmholtz resonators with extended necks > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,929,053 B2 - Document ID: US11929053B2 - Status: Granted - Kind: B2 - Application number: 17/011,786 - Filed: 2020-09-03 - Published: 2021-03-11 - Granted: 2024-03-12 - Earliest claimed: 2019-09-11 - Assignees: The Hong Kong University of Science and Technology - Applicants: The Hong Kong University of Science and Technology - Inventors: Jingwen Guo; Xin Zhang; Yi Fang - Web page: https://patentgrep.com/patent/US11929053B2 ## CPC - G10K 11/168: Plural layers of different materials, e.g. sandwiches - E04B 1/84: Sound-absorbing elements - G10K 11/172: using resonance effects - E04B 2001/8428: {containing specially shaped acoustical bodies, e.g. funnels, egg-crates, fanfolds} - G10K 2210/32272: Helmholtz resonators - G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR - E04B: GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS (border constructions of opening in walls, floors or ceilings E06B1/00; {electromagnetic shielding H05K9/0001}) ## Abstract Sound absorbers using distributed absorption units each having an extended neck are provided. The absorption units can be, for example, Helmholtz resonators with extended neck (HRENs). The absorption units can be distributed in a lateral fashion, for example, in a checkerboard fashion with laterally, non-diagonally adjacent units having a different extended neck length and/or diameter. Each absorption unit can be, for example, a cylinder-structure core sandwiched between a back wall and a perforated plate. ## Claims ### Claim 1 A sound absorber for noise reduction, comprising: a plurality of absorption units, each absorption unit of the plurality of absorption units comprising a cylindrical core disposed between an acoustically rigid back wall and a perforated plate extending in a radial direction of the cylindrical core, each absorption unit of the plurality of absorption units further comprising an extended neck attached to the perforated plate and extending from the perforated plate into the cylindrical core in an axial direction of the cylindrical core that is perpendicular to the radial direction, wherein the extended neck of each absorption unit of the plurality of absorption units is different from the extended neck of each laterally, non-diagonally adjacent absorption unit, wherein the perforated plate of each absorption unit of the plurality of absorption units comprises exactly one opening therein connecting an inside of the cylindrical core to an outside of the sound absorber, wherein the absorption units of the plurality of absorption units are disposed in a checkerboard fashion, where the extended neck of each absorption unit of the plurality of absorption units is the same as the extended neck of each diagonally adjacent absorption unit, wherein the plurality of absorption units comprise a first type of absorption unit with an extended neck with a first parameter value and a second type of absorption unit with a second parameter value different from the first parameter value, and wherein all absorption units of the plurality of absorption units are either the first type or the second type. ### Claim 2 (depends on 1) The sound absorber according to claim 1, wherein a length of the extended neck of each absorption unit of the plurality of absorption units is different from a length of the extended neck of each laterally, non-diagonally adjacent absorption unit, the length of the extended neck being a distance in which the extended neck extends from the perforated plate into the cylindrical core in the axial direction. ### Claim 3 (depends on 1) The sound absorber according to claim 1, wherein a diameter of the extended neck of each absorption unit of the plurality of absorption units is different from a diameter of the extended neck of each laterally, non-diagonally adjacent absorption unit. ### Claim 4 (depends on 1) The sound absorber according to claim 1, wherein the first parameter value is a first length of the extended neck and the second parameter value is a second length of the extended neck, the first length of the extended neck being a distance in which the extended neck extends from the perforated plate into the respective cylindrical core in the axial direction, and the second length of the extended neck being a distance in which the extended neck extends from the perforated plate into the respective cylindrical core in the axial direction. ### Claim 5 (depends on 1) The sound absorber according to claim 1, wherein the first parameter value is a first diameter of the extended neck and the second parameter value is a second diameter of the extended neck. ### Claim 6 (depends on 1) The sound absorber according to claim 1, wherein the second parameter value is larger than the first parameter value, and wherein a difference between the second parameter value and the first parameter value is no more than 40% of the second parameter value. ### Claim 7 (depends on 1) The sound absorber according to claim 1, wherein the second parameter value is larger than the first parameter value, and wherein a difference between the second parameter value and the first parameter value is at least 50% of the second parameter value. ### Claim 8 (depends on 1) The sound absorber according to claim 1, wherein each absorption unit of the plurality of absorption units is made of metal or a photosensitive resin. ### Claim 9 (depends on 1) The sound absorber according to claim 1, wherein each absorption unit of the plurality of absorption units achieves a peak absorption of incident acoustic energy at its resonance frequency. ### Claim 10 (depends on 1) The sound absorber according to claim 1, wherein a thickness of each absorption unit of the plurality of absorption units is smaller than a quarter wavelength of an incident wave. ### Claim 11 (depends on 1) The sound absorber according to claim 1, wherein a total thickness of the sound absorber is 30 millimeters (mm) or less, and wherein a distance in which the extended neck, of each absorption unit of the plurality of absorption units, extends from the perforated plate into the cylindrical core in the axial direction is in a range of from 2 mm to 6 mm. ### Claim 12 (depends on 1) The sound absorber according to claim 1, wherein the sound absorber is configured such that incident acoustic energy arrives from a direction parallel to an axial direction of the cylindrical core of each absorption unit of the plurality of absorption units. ### Claim 13 (depends on 1) The sound absorber according to claim 1, wherein the plurality of absorption units are disposed in a square array.