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Mo. Code Regs. tit. 8 § 50-5.060 : DEPARTMENT OF LABOR AND INDUSTRIAL RELATIONS — Division of Workers' Compensation — Determination of Disability —5.060 - Evaluation of Hearing Disability

PURPOSE: The purpose of this rule is to establish the procedures to evaluate hearing disability, setting forth methods for its measurement and calculation.

(1) The following are definitions relating to this matter and rule:
(A) Hearing loss-the general condition of reduced auditory sensitivity;
(B) Loss of hearing or threshold shift-a change for the worse in auditory sensitivity;
(C) Threshold-the weakest sound that can be heard;
(D) Decibel (dB)-a unit conventionally used to measure the magnitude of sound. In the testing of hearing, it is used to measure the threshold of a listener relative to the standard threshold (U.S. audiometers);
(E) Audiometer-a device for the measurement of the threshold of hearing in decibels relative to a standard;
(F) Hearing level or hearing threshold level-the reading on an audiometer in decibels corresponding to the threshold of hearing of the individual being tested;
(G) Frequency-the number of regular fluctuations made by a sound wave in one (1) second;
(H) Cycle-one (1) of a repeated series of regular fluctuations made by a sound wave;
(I) Audiogram-a chart showing hearing levels at different frequencies;
(J) Hearing disability or disability of hearing-a malfunction or abnormality of hearing of sufficient severity to constitute a practical handicap such as would justify compensation; particularly a reduction of efficiency in everyday communication by speech;
(K) Deafness-term reserved to designate very severe or total disability of hearing;
(L) Presbycusis-a loss of hearing occasioned by the aging process; and
(M) "Hearing level" is a technical term that refers to the point (or threshold) in decibels when a testing sound is first detected by the listener. The "lowest hearing level," therefore, represents best hearing not worst hearing. The "lowest measured loss," therefore, is reflected by the lowest decibel rating at which the listener heard the test tone.
(2) Weeks of compensation for hearing loss due to a traumatic incident (that is, a single accident such as an explosion, a blast or a blow on the head) shall be those provided in items 27 and 28 of subsection 1 of section 287.190, RSMo. (Complete deafness of both ears-one-hundred eight (180) weeks; complete deafness of one (1) ear, the other being normal-forty-nine (49) weeks.)
(3) Weeks of compensation for hearing loss due to prolonged exposure to harmful noise in employment (that is, an occupational disease) shall be those provided in subsection 3 of section 287.197, RSMo.
(4) Traumatic occupational hearing loss(es) shall be measured as prescribed in section 287.197, RSMo and this rule.
(5) When both ears show hearing disability, the computation of disability shall be on the basis of binaural loss as provided in subsection 5 of section 287.197, RSMo.
(6) Liability for occupational hearing loss occurs only when an employee has been exposed to the hazard of such loss for a period of ninety (90) days or longer and the loss becomes exclusively that of the employer in whose employment such exposure took place.
(7) Each employer is liable for all of the occupational hearing loss to which his/her employment contributed, subject to the limitations of the measurement of hearing loss provisions, but no employer is liable for hearing loss sustained prior to employment with him/her nor for any hearing loss for which compensation previously was awarded or paid (section 287.197.8).
(8) The date of disability of occupational hearing loss is the last day of a one (1)-month period following separation from the employment in which the employee was exposed to harmful noise (section 287.197.7).
(9) Claim for compensation for occupational hearing loss, if maintained, must be made within two (2) years of the date of disability, as defined in section (8) of this rule. The provision of medical attention and/or the payment of compensation will toll the statute, as in other workers' compensation cases (section 287.197.7).
(10) Only pure-tone air-conduction audiometric instruments that meet the standards calibrated to the American National Standards Institute (ANSI) occupational hearing loss reference level standards, including ANSI S3.6, as referred to in section 287.197.2 shall be used for measuring hearing levels.
(11) In the evaluation of hearing disability, only the hearing levels at the frequencies of five hundred (500), one thousand (1,000) and two thousand (2,000) cycles per second shall be considered; provided, however, that if a subject does not hear the test tone at the ninety-five (95) decibel hearing level in any or all of the three (3) frequencies, the value of one hundred (100) decibels shall be used for such frequency(ies) in calculating the average hearing level.
(12) Three (3) separate audiograms, each on different days, shall be made including at least the frequencies of five hundred (500), one thousand (1,000) and two thousand (2,000) cycles per second and the lowest hearing level measured at each of the three (3) frequencies shall be used for the computation of hearing disability. The lowest hearing level at each of the three (3) frequencies shall be added together and the sum divided by three (3) to determine the average hearing level in decibels. If the audiograms show a lowest hearing level at any of these three (3) frequencies that is greater than one hundred (100) decibels, or else no response at all, the value of one hundred (100) dB shall be used for the level at such frequencies in calculating the average hearing level.
(13) In order to allow for the average amount of hearing loss due to nonoccupational causes found in the population at any given age (including presbycusis), there shall be deducted from the average hearing level one-half (1/2) decibel for each year of the employee's age over forty (40) at the time of his/her audiogram. The result shall be termed the corrected average hearing level.
(14) For every decibel that the corrected average hearing level exceeds twenty-six (26) decibels based on the ANSI reference levels, an allowance of one and one-half percent (1 1/2%) shall be made up to the maximum of one hundred percent (100%) which is reached at ninety-three (93) decibels based on the ANSI reference levels. The allowance thus calculated is the monaural percentage disability of hearing in that ear.
(15) Binaural disability of hearing shall be determined by multiplying the percentage of disability in the better ear by five (5), to which result is added the percentage of disability in the poorer ear and dividing the sum of the two (2) by six (6). The result is the evaluation in percentage of binaural hearing disability.
(16) 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.
(17) An employee may work in successive employments where s/he is exposed to harmful noise and sustain an accumulated hearing loss, only a part of which may be the liability of the last employer. Section 287.197.8, RSMo provides that an employer is liable only for the hearing loss to which his/her employment contributed. Each subsequent employer who hires an individual who already has some hearing disability is liable only for the additional disability that develops in its employment, subject to the correction according to age.
(18) The best level of hearing at each of the three (3) frequencies of five hundred (500), one thousand (1,000) and two thousand (2,000) cycles per second is determined by selection from all available audiogram(s) made within six (6) months prior to or three (3) months after the date of employment. Earlier audiogram(s) may be used for this purpose only if none is available that were made during that nine (9)-month period.
(19) The pre-employment average hearing level for the three (3) frequencies is calculated for each ear (section (12) of this rule).
(20) The correction for nonoccupational hearing loss (section (13) of this rule) is applied by subtracting from the average hearing level for each ear one-half (1/2) decibel for each year of the employee's age over forty (40) at the time of his/her audiogram.
(21) If the corrected average hearing level of the pre-employment audiogram(s) in either ear exceeds twenty-six (26) decibels, the percentage of disability is calculated as in sections (14) and (15) of this rule. The employer is liable for the difference in percentage of disability between this value and the percentage of hearing disability calculated from post-employment hearing tests.

8 CSR 50-5.060

AUTHORITY: section 287.650, RSMo 2000.* Original rule filed Sept. 11, 1959, effective Sept. 22, 1959. Amended: Filed Aug. 18, 1967, effective Aug. 29, 1967. Emergency amendment filed Oct. 20, 2005, effective Oct. 30, 2005, expired April 27, 2006. Amended: Filed Oct. 20, 2005, effective May 30, 2006.

*Original authority: 287.650, RSMo 1939, amended 1949, 1961, 1980, 1993, 1995, 1998.