Comparison of thresholds acquired with ASSR and PTA in normal-hearing subjects

Objective: To provide new objective technology in evaluating hearing loss for forensic expert by comparing the thresholds acquired with auditory steady-state responses (ASSR) and pure tone audiometry (PTA) in our laboratory.

Methods: Twenty-seven subjects with normal hearing (54 ears, 18-28 years) were tested with PTA and ASSR at 500, 1000, 2000 and 4000 Hz. Paired t-test analysis was performed on threshold of ASSR and PTA at difference frequency (500, 1000, 2000 and 4000 Hz).

Results: At each frequency (500, 1000, 2000 and 4000 Hz), the thresholds acquired with ASSR were higher than those acquired with PTA (P<0.05). The mean difference of each frequency were (22.04+/-5.79) dB (500 Hz), (11.02+/-5.44) dB (1000 Hz), (12.59+/-5.89) dB (2000 Hz) and (17.78+/-7.25) dB (4000 Hz). The mean difference between the system automatically adjusted threshold of ASSR and PTA were (-3.96+/-5.79) dB at 500 Hz, (0.02+/-5.44) dB at 1000 Hz, (-0.41+/-5.89) dB at 2000 Hz, and(-1.25+/-7.25) dB at 4000 Hz.

Conclusions: At each frequency (500, 1000, 2000 and 4000 Hz), the thresholds acquired with ASSR were higher than those acquired with PTA. The mean difference is 16.9 dB. As an objective and mature method, ASSR could be used in evaluation of hearing-loss degree for forensic expert. But adjusted threshold value should be established when ASSR is used to estimate hearing threshold in each laboratory.