Unless otherwise provided by any statute the rules of evidence observed by courts need not be observed, but the rules of privilege recognized by law shall be given effect. Objections to evidentiary offers may be made and shall be noted in the record. Irrelevant or unduly repetitious evidence or cross-examination may be excluded. Subject to these requirements, for the purpose of expediting hearings and when the interests of parties will not be substantially prejudiced thereby, the submission of all or part of the evidence in written form may be permitted, provided that nothing herein shall be construed as requiring that such a submission be permitted.