Muffler

A muffler comprising:

• a case having opposed ends closed;
• at least one partition plate installed in the case to divide an interior of the same into two chambers;
• a sound shielding wall structure installed in one of the two chambers to divide the same into first and second sound chambers allowing the other one of the two chambers to serve as a third sound chamber;
• and
• pipe members projected into the case passing through the partition plate and the sound shielding wall structure to define in the case a sound silencing path including the first, second and third sound chambers,
• wherein the sound shielding wall structure comprises:
• first and second partition plates;
• a positioning structure that puts the first and second partition plates together to keep a given distance therebetween;
• a first group of projections defined by the first partition plate and projected toward the second partition plate, each projection of the first group having a first opening formed therethrough;
• and
• a second group of projections defined by the second partition plate and projected toward the first partition plate, each projection of the second group having a second opening formed therethrough, the projections of the second group respectively facing the projections of the first group having a given clearance kept therebetween.