Sec. 351.6. Proper deductions for presbycusis and other nonindustrial causes of hearing impairment

With respect to presbycusis, no allowance should be made for the possible effect of age on the hearing level. With respect to the possible effect of nonindustrial causes of an individual's hearing impairment other than presbycusis, determination of the amount of loss due to such other causes should be made by the examining otologist. The opinion of the examining otologist as to the etiological factors responsible for the patient's hearing loss, and the extent to which each contributed to such loss, together with all other pertinent data, should be taken into consideration in fixing the amount of the award to be paid.