In this chapter, the following terms have the meanings indicated. Terms Defined. “Background sound level” means wind effects, and sound emission from sources other than the vessel being monitored. “Economic hardship” means a determination by the Department of Natural Resources that, in order to meet the noise level limits as established in Regulation .03 of this chapter: A vessel must have a new muffler installed or the engine must be physically changed; and The cost of the muffler or physical change exceeds 10 percent of the value of the vessel as shown in a national publication of used vessel values used by the Department. “Muffler” means an exhaust system installed below or above the water line and a device that is capable of reducing the noise from the engine to levels that shall meet the noise level limits established by the Department. “Service person” means a person who is employed as a marine engine mechanic, either for himself or by a bona fide engine or boat manufacturer, or marine service company.