The regulations imposed under the authority of this Division 14 may be amended from time to time by ordinance after the ordinance establishing the regulations has gone into effect, but no amendment shall be made without a hearing before a commission or committee designated by the corporate authorities of the municipality. A notice of the time and place of such a hearing shall be given at least once, not more than 30 nor less than 15 days before the hearing, by publishing a notice thereof in one or more newspapers published in the municipality, or, if no newspaper is published therein, then in one or more newspapers with a general circulation within the municipality. In municipalities with less than 500 population in which no newspaper is published, publication may instead be made by posting a notice in 3 prominent places within the municipality. An amendment shall not be passed except by a favorable vote of two-thirds of the members of the city council then holding office in cities or members of the board of trustees then holding office in villages or incorporated towns.