Patent ID: 8136629

Claim:
A muffler comprising: An outer tube defining an outer wall, An inner tube provided in said outer tube and A sound absorbing material filled between said outer tube and said inner tube, and which is attached to an exhaust pipe for exhausting exhaust gas from an engine, The inner tube comprising: A flattened face portion on opposite surfaces thereof causing the inner tube to have a flattened shape, a pair of main flow paths extending in a longitudinal direction on each lateral side of the inner tube side, A recess formed in each of said flattened face portions between the pair of main flow paths, the recess causing portions of each of the flattened face portions to project inwardly toward each other, and A number of punching holes formed in each of the flattened face portions of said inner tube being greater than the number of punching holes formed at edge portion sides of the flattened face portions of said inner tube.