Okla. Stat. tit. 47, § 47-12-402: Mufflers or other noise-suppressing systems -

Prevention of excessive or unusual noise.

A. Every vehicle shall be equipped, maintained, and operated so

as to prevent excessive or unusual noise. Every motor vehicle shall

at all times be equipped with a muffler or other effective noise-

suppressing system in good working order and in constant operation,

and no person shall use a muffler cut-out, bypass or similar device.

No person shall modify the exhaust system of a motor vehicle in any

manner which will amplify or increase the noise or sound emitted

louder than that emitted by the muffler originally installed on the

vehicle.

B. The engine and power mechanism of every motor vehicle shall

be so equipped and adjusted as to prevent the escape of excessive

fumes or smoke, or both.