# US 11,441,515 B2 · Sound absorber > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,441,515 B2 - Document ID: US11441515B2 - Status: Granted - Kind: B2 - Application number: 16/572,885 - Filed: 2019-09-17 - Published: 2020-05-07 - Granted: 2022-09-13 - Earliest claimed: 2018-10-08 - Assignees: ROLLS-ROYCE plc - Applicants: ROLLS-ROYCE plc - Inventors: Paul B. Murray - Web page: https://patentgrep.com/patent/US11441515B2 ## CPC - F02K 1/827: {Sound absorbing structures or liners} - G10K 11/172: using resonance effects - B64D 33/06: {Silencing exhaust or propulsion jets} - F02C 7/045: having provisions for noise suppression - F16L 55/033: Noise absorbers (F16L55/027 takes precedence) - G10K 11/162: Selection of materials - G10K 11/168: Plural layers of different materials, e.g. sandwiches - F02K: JET-PROPULSION PLANTS (features of jet-propulsion plants common to gas-turbine plants, air intakes or fuel supply control of air-breathing jet-propulsion plants F02C7/00, F02C9/00) - 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 - B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT - F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00) - F16L: PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL ## Abstract A sound absorber for an engine of an aircraft, the sound absorber comprising: a base body having a bottom plate, a wall enclosing the bottom plate and an opening enabling entry of air into the base body; and a porous tongue having a fixed end connected to the wall and a free end; wherein the tongue is porous. ## Claims ### Claim 1 A sound absorber for an engine of an aircraft, the sound absorber comprising: a base body having a bottom plate, a wall enclosing the bottom plate and an opening enabling entry of air into the base body; and a tongue having a fixed end connected to the wall and a free end; wherein the tongue is porous, and wherein the tongue has a normalised specific acoustic resistance not less than 0.5 ρc and not more than 10.0 ρc, where ρ is the density of the air and c is the speed of sound through the air. ### Claim 2 (depends on 1) The sound absorber of claim 1, wherein the tongue has a normalised specific acoustic resistance not less than 1.0 ρc, where ρ is the density of the air and c is the speed of sound through the air. ### Claim 3 (depends on 1) The sound absorber of claim 1, wherein the tongue has a normalised specific acoustic resistance not less than 2.0 ρc, where ρ is the density of the air and c is the speed of sound through the air. ### Claim 4 (depends on 1) The sound absorber of claim 1, wherein the tongue has a normalised specific acoustic resistance not less than 3.0 ρc, where ρ is the density of the air and c is the speed of sound through the air. ### Claim 5 (depends on 1) The sound absorber of claim 1, wherein the tongue has a normalised specific acoustic resistance not more than 5.0 ρc, where ρ is the density of the air and c is the speed of sound through the air. ### Claim 6 (depends on 1) The sound absorber of claim 1, wherein the tongue has a central portion disposed between the fixed end and the free end, the tongue further having a longitudinal direction (L) extending from the fixed end towards the free end, a width direction (Br) extending substantially perpendicularly to the longitudinal direction (L), and a transverse direction (Q) extending substantially perpendicularly to the longitudinal direction (L) and substantially perpendicularly to the width direction (Br), the central portion having a first free edge extending in the longitudinal direction (L) from the fixed end towards the free end, and a second free edge opposite to the first free edge and extending in the longitudinal direction (L) from the fixed end towards the free end. ### Claim 7 (depends on 6) The sound absorber of claim 6, wherein the tongue divides a space of the base body into a partial space adjacent to the bottom plate and a partial space adjacent to the opening, the two partial spaces being connected to each other via a gap, the free end being disposed at a first distance from the wall in the transverse direction (Q) and at a second distance from the bottom plate in the longitudinal direction (L), such that the first and the second distances determine a size of the gap. ### Claim 8 (depends on 6) The sound absorber of claim 6, wherein the central portion is configured to extend at least partially straight along the width direction. ### Claim 9 (depends on 1) The sound absorber of claim 1, wherein at least the central portion has two lateral portions extending in the longitudinal direction, with the lateral portions being connected with the wall. ### Claim 10 (depends on 1) A sound absorber assembly for an engine of an aircraft, the sound absorber assembly comprising a plurality of sound absorbers of claim 1. ### Claim 11 (depends on 1) A gas turbine engine for an aircraft comprising the sound absorber of claim 1. ### Claim 12 (depends on 10) A gas turbine engine for an aircraft comprising the sound absorber assembly of claim 10. ### Claim 13 (depends on 11) The gas turbine engine of claim 11, comprising: an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades; and a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft. ### Claim 14 (depends on 13) The gas turbine engine according to claim 13, wherein: the turbine is a first turbine, the compressor is a first compressor, and the core shaft is a first core shaft; the engine core further comprises a second turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor; and the second turbine, second compressor, and second core shaft are arranged to rotate at a higher rotational speed than the first core shaft. ### Claim 15 A sound absorber for an engine of an aircraft, the sound absorber comprising: a base body having a bottom plate, a wall enclosing the bottom plate and an opening enabling entry of air into the base body; and a porous tongue having a fixed end connected to the wall and a free end, wherein the tongue is bent along a longitudinal direction in an arcuate shape and wherein the tongue has a normalised specific acoustic resistance not less than 0.5 ρc and not more than 10.0 ρc, where ρ is the density of the air and c is the speed of sound through the air. ### Claim 16 (depends on 15) The sound absorber of claim 15, wherein the tongue has the shape of a branch of a parabola in the longitudinal direction, and wherein the tongue is straight in a width direction substantially perpendicular to the longitudinal direction. ### Claim 17 (depends on 16) The sound absorber of claim 16, wherein the tongue comprises a foam or a fiber filling.