Extended high-frequency bone conduction audiometry Calibration of bone conductor transducers in the conventional and extended high-frequency range

Abstract

Objective

To monitor ototoxicity, air conduction (AC) extended high frequency (EHF) thresholds can be measured up to 16 kHz. However, conductive hearing loss might influence these results. This is unfortunate because the EHF thresholds are important to follow the impact of ototoxic medication during therapy. Therefore a suitable bone conduction (BC) transducer and norm values for EHF BC measurements are needed.

Design

In this study three different BC transducers were used: the B71 (Radioear), the KH70 (Präcitronic), and the KLH96 (Westra). Hearing thresholds were measured from 0.125 to 16 kHz using AC transducers (Telephonics TDH39, Sennheiser HDA200), and BC thresholds from 0.25 to 8 kHz with the B71, and from 0.25 to 16 kHz with the KLH96 and KH70.

Study sample

60 ears of 30 normal hearing subjects were measured.

Results

The KLH96 showed the highest output for the high frequencies, and distortion measurements were similar to the KH70. The results show that EHF measurements are possible using the KLH96 and KH70 bone conductors.

Conclusion

EHF BC measurements are reliable when using the KLH96 and KH70 bone conductors. The extended force sensitivity of the used artificial mastoid should be determined for a proper EHF BC calibration.

Keywords:

• Calibration bone conductors
• extended high-frequency audiometry
• ‘false’ air-bone gap at 4kHz
• Bone conduction thresholds between 250Hz and 16kHz

Acknowledgments

Dr. Kimmy Snel-Smit was involved in the experimental setup, recruiting subjects, retrieving data, and presenting the preliminary results of this study. Dr. Utz Richter and Dr. ing. Thomas Fedtke are acknowledged for the discussion we had related to the calibration and the force sensitivity measurements of the B&K 4930 artificial mastoid. Ir. Sander Ubbink and Dr. ir. Emile de Kleine of the UMCG are acknowledged for loaning us a B&K8000 impedance head. Hans Versluis is acknowledged for his textual comments. Siwa A. Versnel is acknowledged for proofreading and textual editing of the final version of this paper. Prof. dr. Robert H. Margolis, the anonymous reviewer, and the Editor-in-Chief Prof. dr. De Wet Swanepoel are acknowledged for their detailed and constructive comments.

Disclosure statement

No potential conflict of interest was reported by the author(s).