Sound Theory

• In order to understand how muffler baffles work, one must first understand the differences between pressure waves and fluid flow. A fluid follows the path of least pressure resistance to flow to a point of zero resistance.
  
  A pressure wave is a harmonic vibration that passes through a fluid and is unaffected by the movement of the fluid vector; it travels only in straight lines until it meets some external resistance. A good metaphor would be that of a flashlight beam in a hurricane. No matter how hard the wind blows, the beam of light will never change until it dissipates or reflects off of something.
  
  

Muffler Geometry

• The inside of a baffled muffler is consciously designed to reflect high-frequency sound waves back onto themselves. It does this by employing a series of angled plates, usually in a chevron pattern in the center of the muffler that allow the exhaust to flow smoothly, but reflect the waves back into the wall. Large areas are intentionally left open to allow the exhaust gases to expand, and to allow the longer waved sound to pass through unhindered.
  
  

Muffler Sound Tuning

• Every turn inside of a muffler is designed to cancel out a certain sound frequency, which is dictated by the distance from one turn to the next. A competent sound engineer will include a number of these turns inside the muffler, tuning it to deliver the highest volume of sound in the lowest bass register possible.
  
  

Expansion Chambers

• In order to duct the exhaust through the path of least resistance without being unduly slowed by the baffles, the exhaust must be chambered to provide several opportunities for expansion. Once the exhaust stream has been slowed sufficiently, it is less affected by the sharp angles and less aerodynamic features of the intermediate baffles.
  
  

Baffled vs. Packed

• Baffled mufflers are generally lighter than fiberglass-packing types and are better geared to performance applications. Some straight-through packed designs flow better than their baffled counterparts. But the best of them are in fact a hybrid design, as they include a few baffles within the fiberglass itself to bias the exhaust note toward the bass register.