A Novel Method of Using Passive Electronics to Drive Piezo Transducers in Bone Conduction Hearing Implants

Karl-Johan Fredén Jansson,1 Johannes Kocher,2 Martin L Johansson2,31Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden; 2Research and Technology, Oticon Medical AB, Gothenburg, Sweden; 3Department of Biomaterials, Institute of Clinical Sciences, Gothenburg University, Gothenburg, SwedenCorrespondence: Karl-Johan Fredén Jansson, Chalmers University of Technology, Department of Electrical Engineering, Gothenburg, 41296, Sweden, Tel +46 31 772 1783, Email [email protected]: Piezoelectric transducers are gaining prominence in hearing implants due to their compatibility with magnetic resonance imaging, but commercial alternatives suffer from excessive power consumption. The objective of this study was to propose and evaluate a method of exclusively using passive electronic components in an implanted electronic circuit with low current consumption for driving of a piezo transducer-based hearing aid implant system.Methods: The study sample was a hearing aid system of a prototype piezo transducer and a commercially available sound processor. Output force level and total harmonic distortion were measured by a skull simulator inside an anechoic test chamber at constant sound pressure levels of 70, 80 and 90 dB SPL. Current consumption measurements and a continuous sound exposure test determined the battery lifetime.Results: The current consumption was 5.6 mA (a battery lifetime of 7– 9 days), the maximum total harmonic distortion was 2.15% at 70 dB SPL and maximum power output was 111.7 dB re. 1 μN at 90 dB SPL.Conclusion: The findings of the passive design presented in this study indicate that piezo transducers can be driven by significantly lower current consumption than today’s commercially available alternatives that are based on active electronics.Keywords: piezo transducer, hearing implant, bone conduction, MR-conditional