ABR Threshold Determination
ABR threshold was determined in accordance with ABR Guidance (version
2.1) issued by British Newborn Hearing Screening Program (NHSP) in
2013(15). For NH subjects, 70 dB SPL was used to elicit a clear response
(CR). A CR was defined as the amplitude of the response exceeded 40nV
and at least 3 times of background noise level(15). For CHL subjects, a
higher start stimulation level of 80 to 90 dB SPL was used according to
their PTA results to gain a CR. The intensity level was then decreased
by10 dB until there was no repeatable response, then smaller increment
and decrement were implemented to determine the real threshold in a
precise step of 5dB. Two experienced audiologists analyzed the results
independently to ensure exact recognition of the threshold.