High-frequency air-conduction and electric bone-conduction audiometry. Comparison of two methods

Area of Science:

• Audiology
• Hearing Science
• Biomedical Engineering

Background:

• Accurate hearing threshold measurements are crucial for diagnosing hearing loss.
• High-frequency (HF) audiometry and electric bone-conduction (EBC) audiometry are advanced techniques for assessing auditory function.
• Understanding the relationship between stimulus intensity and perceived loudness is key for audiometric calibration.

Purpose of the Study:

• To compare the threshold values obtained from HF air-conduction (AC) and EBC audiometry.
• To evaluate the reproducibility of both HF AC and EBC audiometric methods.
• To investigate the necessary corrections for converting EBC stimulus units to decibels for comparable loudness sensation.

Main Methods:

• Thresholds were measured in 147 subjects (9-43 years) using an HF AC audiometer (Interacoustics AS 10 HF) and an EBC audiometer (Audimax 500).
• Reproducibility was assessed in a separate group of 24 subjects.
• Correction factors for EBC stimulus (electric current) to decibels were analyzed based on established formulas.

Main Results:

• The conversion of electric current (i) to decibels using the 40 log (i) re 1 mA factor was confirmed for the Audimax 500.
• An additional frequency-dependent correction is necessary for both AC and EBC audiometers to achieve comparable loudness sensation increases.
• EBC audiometry demonstrated superior reproducibility compared to HF AC audiometry, particularly in the high-frequency range.

Conclusions:

• While the established decibel conversion for EBC stimulus is valid, frequency-dependent corrections are essential for accurate loudness perception comparisons.
• EBC audiometry offers better measurement reliability than HF AC audiometry, especially for high-frequency hearing assessments.
• These findings contribute to refining calibration and interpretation standards for advanced audiometric techniques.