(a) For purposes of Section 2538.36 of the Code, a significant air-bone gap is defined as a difference of 15 decibels or more between the higher air conduction and the lower bone conduction pure tone thresholds at 2 or more succeeding octave frequencies of 500 Hertz through and including 4000 Hertz.

(b) Tests for significant air-bone gap shall be performed in a suitable environment using appropriate equipment to establish threshold values and with appropriate masking procedures employed.