# US 11,441,456 B2 · Tuning a sound profile of a muffler > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,441,456 B2 - Document ID: US11441456B2 - Status: Granted - Kind: B2 - Application number: 16/458,875 - Filed: 2019-07-01 - Published: 2021-01-07 - Granted: 2022-09-13 - Earliest claimed: 2019-07-01 - Assignees: Toyota Motor North America, Inc. - Applicants: Toyota Motor North America, Inc. - Inventors: Stephen E. Freeman; Tyler J. Kass - Web page: https://patentgrep.com/patent/US11441456B2 ## CPC - F01N 1/026: {Annular resonance chambers arranged concentrically to an exhaust passage and communicating with it, e.g. via at least one opening in the exhaust passage} - F01N 1/089: {using two or more expansion chambers in series (F01N1/083, F01N1/084, F01N1/086 take precedence)} - F01N 13/082: {of tailpipe, e.g. with means for mixing air with exhaust for exhaust cooling, dilution or evacuation (F01N13/20 takes precedence)} - G10K 11/162: Selection of materials - G10K 11/1752: {Masking} - F01N 2340/00: Dimensional characteristics of the exhaust system, e.g. length, diameter or volume of the exhaust apparatus; Spatial arrangements of exhaust apparatuses - F01N 2470/00: Structure or shape of exhaust gas passages, pipes or tubes - F01N 2470/02: Tubes being perforated - F01N 2470/16: Plurality of inlet tubes, e.g. discharging into different chambers - F01N 2470/20: Dimensional characteristics of tubes, e.g. length, diameter - F01N 2490/02: Two or more expansion chambers in series connected by means of tubes - F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16) - 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 ## Abstract Apparatuses and methods for tuning a muffler. An apparatus comprises a housing for a muffler, a first inlet pipe, and a second inlet pipe. The housing includes a coupling chamber. The first inlet pipe has a first set of physical features and carries exhaust to the coupling chamber. The second inlet pipe has a second set of physical features and carries the exhaust to the coupling chamber. The first set of physical features varies from the second set of physical features with respect to at least one physical feature such that a first sound waveform passing through the first inlet pipe and a second sound waveform passing through the second inlet pipe are uniquely tuned to thereby tune an overall sound waveform emitted by the muffler. ## Claims ### Claim 1 An apparatus comprising: a housing for a muffler, the housing including a coupling chamber; a first inlet pipe having a first set of physical features, wherein the first inlet pipe opens into the coupling chamber to carry exhaust to the coupling chamber; a second inlet pipe having a second set of physical features, wherein the second inlet pipe opens into the coupling chamber to carry the exhaust to the coupling chamber; and an outlet pipe having a first end that opens into the coupling chamber to receive the exhaust from the coupling chamber, wherein the outlet pipe extends from the first end within the coupling chamber to a second end in an environment outside of the housing, wherein the first set of physical features varies from the second set of physical features with respect to at least one physical feature such that a first sound waveform passing through the first inlet pipe and a second sound waveform passing through the second inlet pipe are uniquely tuned to thereby tune an overall sound waveform emitted by the muffler. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the first sound waveform and the second sound waveform are uniquely tuned with respect to a time domain by a first portion of the first inlet pipe and a second portion of the second inlet pipe that extend through the housing and to the coupling chamber having different lengths. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the first sound waveform and the second sound waveform are uniquely tuned by a first portion of the first inlet pipe and a second portion of the second inlet pipe that extend through the housing and to the coupling chamber having different diameters. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the first sound waveform and the second sound waveform are uniquely tuned by a first portion of the first inlet pipe and a second portion of the second inlet pipe that extend through the housing and to the coupling chamber having different perforation patterns. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the first sound waveform and the second sound waveform are uniquely tuned by either a first portion of the first inlet pipe that extends through the housing and to the coupling chamber or a second portion of the second inlet pipe that extends through the housing and to the coupling chamber having a perforation pattern. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the first sound waveform and the second sound waveform are uniquely tuned by a first portion of the first inlet pipe and a second portion of the second inlet pipe that extend through the housing and to the coupling chamber being at least partially covered by different types of absorption materials. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the first sound waveform and the second sound waveform are uniquely tuned by either a first portion of the first inlet pipe that extends through the housing and to the coupling chamber or a second portion of the second inlet pipe that extends through the housing and to the coupling chamber being at least partially surrounded by an absorption material. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the outlet pipe extends from the coupling chamber to the environment outside of the housing and through which the overall sound waveform is emitted from the muffler, wherein the overall sound waveform is formed by a summation of the first sound waveform and the second sound waveform. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the outlet pipe extends from the coupling chamber, through the housing, to the environment outside of the housing and through which the overall sound waveform is emitted from the muffler, wherein the overall sound waveform is formed by a summation of the first sound waveform and the second sound waveform. ### Claim 10 (depends on 1) The apparatus of claim 1 further comprising: a plurality of outlet pipes that extend from the coupling chamber to outside of the housing. ### Claim 11 A muffler comprising: a housing that includes a coupling chamber; a first inlet pipe having a first set of physical features, wherein the first inlet pipe opens into the coupling chamber to carry exhaust to the coupling chamber; a second inlet pipe having a second set of physical features, wherein the second inlet pipe carries exhaust to the coupling chamber; and an outlet pipe having a first end that opens into the coupling chamber to receive the exhaust from the coupling chamber, wherein the outlet pipe extends from the first end within the coupling chamber to a second end in an environment outside of the housing and that carries the exhaust from the coupling chamber to an environment outside of the housing; wherein the first set of physical features varies from the second set of physical features with respect to at least one physical feature such that a first sound waveform passing through the first inlet pipe and a second sound waveform passing through the second inlet pipe are uniquely tuned to thereby tune an overall sound waveform that passes through the outlet pipe. ### Claim 12 (depends on 11) The muffler of claim 11, wherein the first sound waveform and the second sound waveform are uniquely tuned with respect to at least one of the time domain or the frequency domain by varying at least one of a length, a diameter, a perforation pattern, or an absorption material between a first portion of the first inlet pipe and a second portion of the second inlet pipe. ### Claim 13 A method for tuning inlet pipes of a muffler, the method comprising: forming a first inlet pipe that opens into a coupling chamber and carries exhaust to the coupling chamber within a housing of the muffler such that a first portion of the first inlet pipe has a first set of physical features; and forming a second inlet pipe that opens into the coupling chamber and carries exhaust to the coupling chamber such that a second portion of the second inlet pipe has a second set of physical features; and forming an outlet pipe having a first end that opens into the coupling chamber to receive the exhaust from the coupling chamber, wherein the outlet pipe extends from the first end within the coupling chamber to a second end in an environment outside of the housing, wherein the first set of physical features varies from the second set of physical features with respect to at least one physical feature to configure the first inlet pipe and the second inlet pipe such that a first sound waveform that passes through the first inlet pipe and a second sound waveform that passes through the second inlet pipe are uniquely tuned to thereby tune an overall sound waveform emitted by the muffler. ### Claim 14 (depends on 13) The method of claim 13, wherein forming the first inlet pipe comprises: forming the first inlet pipe such that the first portion of the first inlet pipe has at least one of a different length, diameter, perforation pattern, or absorption material at least partially wrapped around the first portion of the first inlet pipe as compared to the second portion of the second inlet pipe. ### Claim 15 (depends on 13) The method of claim 13, wherein forming the second inlet pipe comprises: forming the second inlet pipe such that the second portion of the second inlet pipe has at least one of a different length, diameter, perforation pattern, or absorption material at least partially wrapped around the second portion of the second inlet pipe as compared to the first portion of the first inlet pipe. ### Claim 16 (depends on 13) The method of claim 13, wherein forming the first inlet pipe comprises: forming the first inlet pipe such that the first portion has a perforation pattern; and wherein forming the second inlet pipe comprises: forming the second inlet pipe such that the second portion has no perforation pattern. ### Claim 17 (depends on 13) The method of claim 13, wherein forming the first inlet pipe comprises: forming the first inlet pipe such that the first portion has no perforation pattern; and wherein forming the second inlet pipe comprises: forming the second inlet pipe such that the second portion has a perforation pattern. ### Claim 18 (depends on 13) The method of claim 13, wherein forming the first inlet pipe comprises: forming the first inlet pipe such that the first portion has an absorption material at least partially wrapped around the first portion; and wherein forming the second inlet pipe comprises: forming the second inlet pipe such that the second portion has no absorption material wrapped around the second portion. ### Claim 19 (depends on 13) The method of claim 13, wherein forming the first inlet pipe comprises: forming the first inlet pipe such that the first portion has no absorption material wrapped around the first portion; and wherein forming the second inlet pipe comprises: forming the second inlet pipe such that the second portion has an absorption material at least partially wrapped around the second portion. ### Claim 20 (depends on 13) The method of claim 13, wherein tuning of the first sound waveform and the second sound waveform causes the overall sound waveform that passes through the outlet pipe to have at least one of a desired sound quality or a desired sound character.