274                              LAWS OF MARYLAND                      [CH. 155

(d)    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 15 decibels an allowance of one and one half
(1½) per cent shall be made up to the maximum of one hundred
(100) per cent which is reached at 82 decibels.

(e)    In determining the binaural percentage of loss, the percent-
age of impairment in the better ear shall be multiplied by five (5).
The resulting figure shall be added to the percentage of impairment
in the poorer ear and the sum of the two divided by six (6). The
final percentage shall represent the binaural hearing impairment.

(f)    Before determining the percentage of hearing impairment,
in order to allow for the average amount of hearing loss from non-
occupational causes found in the population at any given age, there
shall be deducted from the total average decibel loss, one half (½)
decibel for each year of the employee's age over forty at the time of
last exposure to industrial noise.

(g)    Notwithstanding any other provision of this Article, no
claim for scheduled income benefits shall be filed until the lapse of six
full consecutive calendar months after the termination of exposure
to harmful noise in employment. The time limitation for the filing OF
claims for occupational deafness shall not begin to run earlier than
the day following the termination of such six months' period. The
time for filing claim as provided under this paragraph shall be
applicable not only in respect of the last employer, but also in respect
of any prior employer who may have liability to pay compensation
for the occupational deafness.

(h) An employer, otherwise liable under this section, whose
employment has contributed to any extent to the employee's
occupational deafness shall be liable for the full extent of the deaf-
ness of the employee, unless such employer shall establish by com-
petent evidence (including the results of a professionally controlled
hearing test) the extent of the employee's deafness as it existed
prior to exposure to harmful noise in the employer's employment.
Upon such showing the employer shall be liable to the employee only
for the proportion of the deafness attributable to the employment by
him. An employer liable to the employee for the full extent of the
employee's occupational deafness may implead, in a compensation
proceeding on the employee's claim, any prior employer or employers
in whose employment the employee had been exposed to harmful
noise, and if it should be found that the impleaded employer would
have been liable to the employee under this section, had the employee
proceeded against him, under the claim being adjudicated, the
employer held liable shall be entitled to an award against the im-
pleaded employer. The impleading of an employer shall be
accomplished by notice on a form prescribed by the Commission.
Such notice shall be sent to the impleaded employer and to the
Commission. An award may be made in favor of the employer
liable to the employee, and against the impleaded employer or
employers, which award may be enforced in the same manner as
awards to employees. The impleaded employer or employers shall
bear equal shares with the employer of the employer's liability to
the employee, unless the evidence warrants a different apportion-
ment.