# US 9,752,494 B2 · Noise suppression systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,752,494 B2 - Document ID: US9752494B2 - Status: Granted - Kind: B2 - Application number: 14/045,657 - Filed: 2013-10-03 - Published: 2014-09-18 - Granted: 2017-09-05 - Earliest claimed: 2013-03-15 - Assignees: Kohler Co. - Applicants: Kohler Co. - Inventors: Tyler W. Le Roy; Todd A. Baumann; Dale D. Snyder; Amy Adams - Web page: https://patentgrep.com/patent/US9752494B2 ## CPC - F01P 11/12: Filtering, cooling, or silencing cooling-air - F04D 29/4213: {suction ports} - F04D 29/424: {Double entry casings} - F04D 29/582: {specially adapted for elastic fluid pumps} - F04D 29/665: {by means of resonance chambers or interference} - F01P: COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES (arrangements in connection with cooling of propulsion units in vehicles B60K11/00; heat-transfer, heat-exchange or heat-storage materials C09K5/00; {cooling of gas-turbine engines F02C7/12}; heat exchange in general, radiators F28) - F04D: NON-POSITIVE-DISPLACEMENT PUMPS (engine fuel-injection pumps F02M; ion pumps H01J41/12; electrodynamic pumps H02K44/02) ## Abstract An apparatus or system includes a component that generates or transfers noise having a frequency within a noise frequency range. The component may include a boundary. The apparatus or system may be an engine in some examples. The engine may additionally include a micro-perforated sheet positioned a distance from the boundary. The micro-perforated sheet may include a plurality of micro-perforated holes, and may be configured to absorb sound within an absorption frequency range based on parameters of the micro-perforated sheet. The parameters may include the distance from the boundary and dimensions of the micro-perforated holes, and may be set such that the absorption frequency range overlaps the noise frequency range. ## Claims ### Claim 1 An engine comprising: a cylinder that generates or transfers noise having a frequency within a noise frequency range, the cylinder comprising a side surface; a plurality of cooling fins extending radially from the side surface of the cylinder; micro-perforated cylinder wrap comprising a micro-perforated sheet positioned a first lateral distance from the side surface of the cylinder, the micro-perforated sheet positioned proximate to ends of the cooling fins and comprising a plurality of micro-perforated holes, the micro-perforated sheet configured to absorb sound within an absorption frequency range based on parameters of the micro-perforated sheet; wherein the parameters include the distance from a boundary and dimensions of the micro-perforated holes, and wherein the parameters are set such that the absorption frequency range overlaps the noise frequency range; wherein an inner surface of the micro-perforated sheet facing the cylinder is free of acoustic insulation; and wherein the micro-perforated cylinder wrap has a shape that conforms to a shape of the cylinder. ### Claim 2 (depends on 1) The engine of claim 1, wherein the parameters are set such that the absorption frequency range overlaps a portion of the noise frequency range consisting of sound between 300-1500 Hz for tonal noise and sound between 800-3000 Hz for flow noise. ### Claim 3 (depends on 1) The engine of claim 1, wherein the micro-perforated cylinder wrap has a curved shape that conforms to the shape of the cylinder. ### Claim 4 (depends on 1) The engine of claim 1, wherein the micro-perforated cylinder wrap has a flat shape. ### Claim 5 (depends on 1) The engine of claim 1, wherein the micro-perforated cylinder wrap is formed of a metal sheet material. ### Claim 6 An engine comprising: a cylinder that generates or transfers noise having a frequency within a noise frequency range, the cylinder comprising a side surface; a plurality of cooling fins extending radially from the side surface of the cylinder; a micro-perforated cylinder wrap comprising a micro-perforated sheet positioned a first distance from the side surface of the cylinder, the micro-perforated sheet positioned proximate to ends of the cooling fins and comprising a plurality of micro-perforated holes, the micro-perforated sheet configured to absorb sound within an absorption frequency range based on parameters of the micro-perforated sheet; and a baffle wall positioned at a second distance from the cylinder wrap and collectively forming a micro-perforated panel with the micro-perforated sheet, the second distance defining a cavity creating an air space between the baffle wall and the micro-perforated sheet; wherein the parameters include the distance from a boundary and dimensions of the micro-perforated holes, and wherein the parameters are set such that the absorption frequency range overlaps the noise frequency range. ### Claim 7 (depends on 6) The engine of claim 6, wherein the second distance is selected such that the baffle wall is positioned at a distance of lowest wave pressure from the micro-perforated sheet of the cylinder wrap. ### Claim 8 (depends on 6) The engine of claim 6, wherein the second distance equals the first distance. ### Claim 9 An engine comprising: a cylinder that generates or transfers noise having a frequency within a noise frequency range, the cylinder comprising a side surface; a plurality of cooling fins extending radially from the side surface of the cylinder; a micro-perforated cylinder wrap comprising a micro-perforated sheet positioned a first distance from the side surface of the cylinder, the micro-perforated sheet positioned proximate to ends of the cooling fins and comprising a plurality of micro-perforated holes, the micro-perforated sheet configured to absorb sound within an absorption frequency range based on parameters of the micro-perforated sheet; and a baffle wall positioned at a second distance from the cylinder wrap and collectively forming a micro-perforated panel with the micro-perforated sheet, the second distance defining a cavity creating an air space between the baffle wall and the micro-perforated sheet; wherein the parameters include the distance from a boundary and dimensions of the micro-perforated holes, and wherein the parameters are set such that the absorption frequency range overlaps the noise frequency range; wherein the second distance is selected so that the cavity absorbs noise within the noise frequency range of the noise generated by the cylinder.