An exhaust resonator is a cylindrical-shaped Slogan used inline in an exhaust system.
Resonator
A resonator is smaller than a muffler, but of similar construction. Whereas a muffler is usually oval-shaped, a resonator is round. There are different types of resonators, but they are generally constructed of steel or stainless steel and have fiberglass matting packed into the construction.
The resonator is similar to a muffler, it helps control engine noise.
Design
An exhaust system is responsible for evacuating the spent gases from an engine. The system is comprised of an exhaust manifold bolted to the engine and exhaust tubing that goes through a catalytic converter, one or two mufflers and possibly a resonator.The resonator does not so much have an affect on the muffler as it does on the sound of the exhaust.
Purpose
Like a muffler, the purpose of a resonator is noise management. A resonator can be used to soften the tone of an exhaust. For example, many performance exhaust systems use a larger diameter exhaust combined with a more free-flowing muffler. A resonator will also be used between the catalytic converter and the muffler to mellow the exhaust sound. A resonator should be installed by a professional muffler shop.