High-Frequency Audiometry: Comparison of Electric Bone-Conduction and Air-Conduction Thresholds

Abstract

Thresholds have been measured with two commercially available high-frequency (HF) audiometers providing respectively air-conduction (AC) and electric bone-conduction (EBC) stimulation. Normative values for the latter have been obtained, and the reduction of HF sensitivity with both stimulus modes documented in two groups aged 50-59 and 70-79 years. EBC reproducibility is of the same order of magnitude as the AC signal through 14 kHz, while the dynamic range is limited to 50 dB. Lateralization of the EBC signal occurs up to at least 17 kHz. The logarithmic conversion factor of Tonndorf and Kurman [Ann. Otol. Rhinol. Lar. 93: 576-582, 1984] does not result in equivalent AC and EBC thresholds at all frequencies, but does provide similar loudness sensation increases. The 40 log (i) re 1 mA conversion factor must be adjusted with a frequency-dependent additive correction.

Key Words:

• High-frequency hearing
• Air conduction
• Electric bone-conduction
• Electrical stimulation
• Bone-conduction theories