5-5-5: USE DISTRICT NOISE LEVELS:
   A.   Maximum Permissible Sound Levels: It shall be a violation of this chapter for any person to operate or permit to be operated any stationary source of sound which creates a sound level greater than fifteen (15) dB(A) above the ambient sound level (L90) for any measurement period which exceed the limits set forth for the following receiving land use districts when measured at the boundary or at any point within the property affected by the noise:
      L90      L10
   Use District   9PM - 7AM   7AM - 9PM   9PM - 7AM   7AM - 9PM
   Residential   50 dB(A)   55 dB(A)   60 dB(A)   65 dB(A)
   Commercial   55 dB(A)   60 dB(A)   65 dB(A)   70 dB(A)
   Industrial   65 dB(A)   70 dB(A)   75 dB(A)   80 dB(A)
When a noise source can be identified and its noise measured in more than one land use category, the limits of the restrictive use shall apply at the boundaries between different land use categories. For the purpose of enforcing these provisions, a measurement period shall not be less than ten (10) minutes nor more than thirty (30) minutes.
   B.   Correction For Character Of Sound:
      1.   For any stationary source of sound which emits a pure tone, cyclically varying sound or repetitive impulsive sound, the limits set forth in subsection A above shall be reduced by five (5) dB(A).
      2.   Notwithstanding compliance with subsection B1 of this section, it shall be a violation of this chapter for any person to operate or permit to be operated any stationary source of sound which emits a pure tone, cyclically varying or repetitive impulsive sound which creates a noise disturbance. (1984 Code § 23A-4)