Upon the filing of the resolution and map with the commission, it shall view the real estate to be acquired under the resolution and fix a time and place for the hearing when and where the owners and all persons interested may be heard. Notice of the time and place shall be given by at least one publication in a newspaper circulating in the municipality or municipalities in which the real estate is situated not less than ten days before the hearing. Notice of the time and place of the hearing shall also be mailed to the owners of the real estate to be taken, directed to their last known postoffice address, at least one week before the day set for the hearing, but failure to mail any notice shall not invalidate any proceedings hereunder. The notice shall be mailed and published by such clerk or other officer as the commission may designate.