Here is what the forest service says about testing for sound
Sound Levels
Increased OHV use and the popularity of aftermarket mufflers means more noise. Noise buffers are located between residential and recreational riding areas, and are closed to motorized travel. Vehicle sound is measured by a decibel meter positioned 20 inches and 45 degrees from the exhaust outlet. Have your vehicle checked! Forest personnel are equipped to provide sound checks. Vehicles operating over the decibel limit are subject to citation
Decibel limit for Oregon Dunes National Recreation Area is 93 decibels.
Find out more about noise limits and sound tests for the Oregon Dunes .
Decibel limit for Sand Lake Recreation area is 97 decibels.