Walker CV Technical Support

U.S. EPA Noise Regulations For On Road Trucks

The first nationwide regulation of truck noise was established with the Noise Control Act of 1972 (P.L. 92-574-86 STAT.1234). Regulations apply to trucks greater than 10,000 lbs GVW. Noise regulations apply to total truck noise, not just exhaust noise. The five major sources of noise in trucks are:

Fan Noise
Air Intake
Mechanical Noise (Engine and Drive Train)
Tires
Exhaust

Aftermarket Regulations For Total Truck Noise When Measured at 50 Feet Are:

Trucks 1986 model year and newer 83dBA

Trucks 1985 model year and older 86dBA

Usage of the mufflers as recommended in the noise charts by engine application and as recommended in the individual exhaust schematic contained by application will help ensure compliance with the regulations.

Maintenance Tips to Assist in Reduction of Exhaust Noise:

Check flex tubing regularly. Repair worn or leaking tubing.
Make sure the exhaust system is properly supported with required brackets, clamps, and braces.
Check strap seal band clamps to ensure properly tightened to avoid leaks.
Consider acoustic compound when repairing OD-ID connections.

Noise Reduction Tips :

Make sure your muffler is recommended by the muffler manufacturer for the engine it is installed on. To meet most new noise laws, the "universal" muffler must be replaced by a muffler designed specifically for the engine.
Tail pipes on horizontal exhaust systems should be tipped toward the center of the vehicle to avoid noise reflection off the road.
If you have curved stacks, replace them with straight stacks. Noise coming from a pipe outlet is directional and straight stacks will throw the noise up, not to the side. Rain caps and 45 degree cut stacks do not appreciably affect noise levels.
The length of the stack installed on the muffler can be critical. If an irritating "rap" is heard at certain engine speeds, try stacks with different lengths.
On exhaust systems with piping exceeding 10 feet in length, the muffler is suggested to be installed where the exhaust pipe to the muffler is either one-half or four times the length of the tail pipe.
A resonator can be used in-line with the recommended muffler for additional noise reduction.
If you have increased the size of the exhaust piping or made a dual out of a single system, check recommendations for piping size. Over-sized systems are excessively noisy! Holes or poorly clamped connections on exhaust piping are also noisy.
The vehicle operator, to a certain extent can control his vehicle noise. The greater the engine load the louder the noise. Certain engine speeds may be more noisy than others. High vehicle speed causes more tire noise. Operating an engine brake when it's not needed may cause extra noise.
If the above-mentioned techniques do not solve your problem, contact Walker for specific recommendations.