Reference zero for the calibration of bone-conduction audiometric equipment using short-duration signals

Area of Science:

• Audiology
• Auditory Neuroscience
• Biomedical Engineering

Background:

• Auditory brainstem responses (ABRs) are crucial for assessing hearing function.
• Standardized calibration for ABRs, particularly tonebursts, relies on ISO 389-6 (2007).
• Current standards lack specific bone-conduction (BC) transducer values, necessitating estimations in clinical practice.

Purpose of the Study:

• To provide empirical bone-conduction (BC) values for toneburst stimuli used in ABR testing.
• To supplement the existing ISO 389-6 (2007) standard by offering missing BC calibration data.
• To establish a reliable reference for BC measurements in ABR assessments.

Main Methods:

• Employed a RadioEar B81 bone vibrator to determine Equivalent Threshold Vibratory Force Levels (ETVFLs).
• Followed test procedures aligned with ISO 389-9 (2009).
• Utilized the peak-to-peak equivalent method for level characterization in 27 otologically normal adults.

Main Results:

• Median thresholds for 0 dB HL were determined across various frequencies (0.5, 1, 2, 4 kHz).
• Specific toneburst values with contralateral masking were found to be 68 dB re: 1 µN (0.5 kHz), 60.5 dB (1 kHz), 47.5 dB (2 kHz), and 44.5 dB (4 kHz).
• The click reference value with contralateral masking was established at 58 dB re: 1 µN.

Conclusions:

• The generated empirical BC values can form a basis for updating ISO 389-6 (2007).
• These data address the current deficit in standardized BC calibration for ABRs.
• Provides clinicians with empirical data for more accurate BC threshold estimations.