39-71-805. Determining percent of hearing loss. (1) The percent of hearing loss, for purposes of the determination of compensation claims for occupational deafness, shall be calculated as the average in decibels of the thresholds of hearing for the frequencies of 500, 1,000, and 2,000 cycles per second. Pure tone air conduction audiometric instruments, approved by nationally recognized authorities in this field, shall be used for measuring hearing loss. If the losses of hearing average 25 decibels or less in the three frequencies, as measured under ISO Standard 1964, such losses of hearing shall not then constitute any compensable hearing disability. If the losses of hearing average 92 decibels or more in the three frequencies, as measured under ISO Standard 1964, then the same shall constitute and be total or 100% compensable hearing loss.
     (2) In measuring hearing impairment, the lowest measured losses in each of the three frequencies shall be added together and divided by three to determine the average decibel loss. For every decibel of loss exceeding 25 decibels, an allowance of 1 1/2% shall be made up to the maximum of 100%, which is reached at 92 decibels.
     (3) In determining the binaural percentage of loss, the percentage of impairment in the better ear shall be multiplied by five. The resulting figure shall be added to the percentage of impairment in the poorer ear and the sum of the two divided by six. The final percentage shall be representative of the binaural hearing impairment.
     (4) Before determining the percentage of hearing impairment, in order to allow for the average amount of 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 40 at the time of last exposure to industrial noise.
     (5) No consideration shall be given to the question of whether or not the ability of an employee to understand speech is improved by the use of a hearing aid.

     History: En. 92-710 by Sec. 1, Ch. 366, L. 1971; amd. Sec. 1, Ch. 381, L. 1973; R.C.M. 1947, 92-710(1)(b) thru (f).