This provision is an "objective emission" control. It can define the method of vehicle operation that is used to define the maximum permitted sound level. It can have a curfew. Some states exempt motor vehicle racing events from noise disturbance litigation or prosecution. Arizona (Section 28-955.03) exempts racing motorcycles from maximum sound levels and muffler requirements. Illinois {Section 35.903} had detailed regulations on racing vehicles It required a 14 dB reduction in sound output, limited sound output at half mater to 115 dB(A), and no more than 105 dB(A) at 50 feet.