It is unlawful for any person willfully to cause, or, being in possession of real property, a motor vehicle, equipment or other source of sound willfully to allow sound to emanate from such property, vehicle or equipment which is plainly audible within any dwelling unit located within a residentially zoned district of the city and which sound is of such loudness, frequency, duration, or unreasonable time of the day as to unreasonably disturb the peace and comfort of owners or possessors of dwelling units within such residential district when such owners or possessors are within such dwelling units. Provided, however, that this prohibition shall not apply to sounds created by emergency equipment operated by law enforcement, fire department or medical emergency personnel. A violation of this section shall constitute a misdemeanor. (Ord. 913 §1, 1991).