Standardization of calibration scheme in NB Chirp ABR Hearing Assessment: A Preliminary Study Based on Normal Hearing Soldiers

Abstract Background: Optimal medical intervention for veterans suffering from military noise-induced hearing impairment is a major concern of the specialists in military medicine, otology, and audiology sectors. Thus, it is important to objectively and accurately reflect the hearing level of the subject in the intervention to aid hearing and improve the existing hearing disability evaluation program. Purpose: The present study intends to identify the optimal correction scheme by comparing the accuracy and range of deviation of narrow-band chirps evoked auditory brainstem responses (NB Chirp ABR) corrected by different schemes in estimating the hearing level of people with normal hearing. Methods: A total of 66 individuals could hear sounds of a frequency <25dB hearing level (HL) in the pure tone audiometry were randomly divided into a model group (26 subjects), test group 1 (with 20 subjects), and test group 2 (with 20 subjects). The mean threshold difference and the regression equation at each frequency were obtained through the model group, and the correction results of the “mean threshold difference scheme (S1)” and the “regression equation scheme (S2)” were compared in the test groups 1 and 2. All data were analyzed using SPSS 24.0. Results: 1) The accuracy of the estimated hearing level (eHL) of non-corrected NB Chirp ABR was significantly higher than that of NB Chirp ABR corrected by S1 or S2; 2) The range of deviation of the eHL of non-corrected NB Chirp ABR from the pure tone audiometry threshold was greater than that of NB Chirp ABR corrected by S1 or S2 from the pure tone audiometry threshold at 500 and 1000 Hz, while at 2000 and 4000 Hz, the values were similar. Conclusion: Among people with normal hearing, it was necessary to correct NB Chirp ABR at 500 and 1000 Hz for higher accuracy of the eHL, but the strengths of different correction schemes were not defined. For clinical convenience, the “mean threshold difference scheme,” with the correction values of 7 and 4 dB, was recommended for correction. At 2000 and 4000 Hz, it was not necessary to correct NB Chirp ABR. Thus, additional subjects with different HLs should be included in future studies to discuss the differences between the two schemes.