Every deaf person whose appearance at a proceeding entitles the person to an interpreter shall notify the appointing authority of the person’s disability at least two weeks prior to any appearance and shall request the services of an interpreter. An appointing authority may require a person requesting the appointment of an interpreter to furnish reasonable proof of the person’s disability when the appointing authority has reason to believe that the person is not so disabled. Reasonable proof shall include but not be limited to a statement from a doctor, an audiologist, the vocational rehabilitation division of the public education department, the commission for deaf and hard-of- hearing persons or a school nurse that identifies the person as deaf or as having hearing so seriously impaired as to prohibit the person from understanding voice communications.