No construction or alteration operations shall be carried on between the hours of ten p.m. and six a.m. if the same are accompanied by loud or annoying noises, in any block in which more than one-half of the buildings on either side of the street are used for residential purposes; provided, however, that nothing in this section shall be construed to prohibit any work necessary at any time to prevent imminent injury to persons or property. (Ord. 1977-10 § 6-6, 1977)