S.D. Codified Laws § 62-9-5

Before determining the percentage of hearing impairment, in order to allow for the average hearing loss from nonoccupational causes found in the population at any given age, there shall be deducted from the total average decibel loss, one-half decibel for each year of the employee's age over forty-five years at the time of last exposure to occupational noise. Other appropriate deductions established by competent specialist opinion which exceed the foregoing allowance for presbycusis shall also be deducted.