Whoever shall knowingly and wilfully utter any false air raid alarm signal or warning or who shall simulate any official air raid signal or warning or shall wilfully break, injure or remove any mechanical warning or signal device used therefor shall be guilty of a misdemeanor, and, upon conviction thereof, shall be sentenced to pay a fine not exceeding one thousand dollars ($1,000), or imprisonment for a term not exceeding two (2) years, or both: Provided, however, That any air raid alarm signal or warning uttered by any person in connection with any duly authorized air raid drill or practice blackout shall not be deemed to be a false air raid alarm signal or warning within the meaning of this section.