Acoustic metamaterial-based muffler for broadband exhaust noise reduction of internal combustion engines

An acoustic metamaterial-based muffler for broadband exhaust noise reduction of internal combustion engines that is mounted on an exhaust pipe of an internal combustion engine, comprising:

• an exhaust flow pipe that is formed of an inlet on one side through which exhaust of the internal combustion engine flows in, an outlet on the other side through which the exhaust flows out, and a flow passage on an inside through which the exhaust flows from one side to the other side;
• and
• a plurality of noise reduction units that are provided inside along a longitudinal direction of the exhaust flow pipe to attenuate noise in the corresponding frequency band among the exhaust noises flowing along the exhaust flow pipe,
• wherein the plurality of noise reduction units includes a first noise reduction unit that attenuates exhaust noise in the frequency bands of 296 to 367 Hz, 374 to 804 Hz, 962 to 1349 Hz, 1401 to 1784 Hz, and 1824 to 2000 Hz among the frequency ranges of 1 to 2000 Hz, and
• wherein the first noise reduction unit includes:
• a first front outer wall that is formed orthogonal to a longitudinal direction of the exhaust flow pipe,
• a first rear outer wall that is spaced apart from the first front outer wall at a certain distance, and formed orthogonal to the longitudinal direction of the exhaust flow pipe,
• a 1-1 inner wall that is formed by a first pair of opposing walls formed at respective ends of the first front outer wall and the first rear outer wall to have a length toward an inner center between the first front outer wall and the first rear outer wall, and of which length is parallel to the longitudinal direction of the exhaust flow pipe,
• a 1-2 inner wall that is spaced apart from the 1-1 inner wall at a corresponding distance in an outer circumferential direction on an inside between the first front outer wall and the first rear outer wall, and is formed by a second pair of opposing walls formed at the first front outer wall and the first rear outer wall, respectively, to have a length toward the inner center between the first front outer wall and the first rear outer wall, and of which length is parallel to a length of the 1-1 inner wall,
• a 1-3 inner wall that is spaced apart from the 1-2 inner wall at a corresponding distance in the outer circumferential direction on the inside between the first front outer wall and the first rear outer wall, and is formed by a third pair of opposing walls formed at the first front outer wall and the first rear outer wall, respectively, to have a length toward the inner center between the first front outer wall and the first rear outer wall, and of which length is parallel to the length of the 1-1 inner wall, and
• a 1-4 inner wall that is spaced apart from the 1-3 inner wall at a corresponding distance in the outer circumferential direction on the inside between the first front outer wall and the first rear outer wall, and is formed by a fourth pair of opposing walls formed at the first front outer wall and the first rear outer wall, respectively, to have a length toward the inner center between the first front outer wall and the first rear outer wall, and of which length is parallel to the length of the 1-1 inner wall.