Found the law online:
- Mufflers and exhaust systems. Prevention of noise. Every motor
vehicle, operated or driven upon the highways of the state, shall at all
times be equipped with an adequate muffler and exhaust system in
constant operation and properly maintained to prevent any excessive or
unusual noise and no such muffler or exhaust system shall be equipped
with a cut-out, bypass, or similar device. No person shall modify the
muffler or exhaust system of a motor vehicle in a manner which will
amplify or increase the noise emitted by the motor or exhaust system of
such vehicle above that emitted by the muffler or exhaust system
originally installed on the vehicle and such original muffler and
exhaust system shall comply with all the requirements of this section.
A muffler is a device consisting of a series of chambers or baffle
plates, or other mechanical design for the purpose of receiving exhaust
gas from an internal combustion engine, and effective in reducing noise.
An exhaust system is a series of mechanical devices for the purpose of
receiving exhaust gas from an internal combustion engine and expelling
it into the atmosphere.