All adjudicative proceedings shall be open to public observation except that a party may apply for a protective order to close part or all of a hearing. The party making the request shall state the reasons for making the application to the presiding officer. If the other party opposes the request, a written response to the request shall be made to the presiding officer. The presiding officer shall determine which, if any, parts of the proceeding shall be closed, and state the reasons therefor in writing.