[Intraoperative evaluation of signal transduction of prototypes of implantable hearing aid transducers in the human].

During routine middle ear surgery prototypes of implantable piezoelectric hearing aid transducers were coupled to the ossicular chain of 28 patients. Pure tone thresholds in a broad frequency range (250 Hz-8 kHz) and perception of music were the basis of psychoacoustic evaluation of the transfer properties of the prototypes in this human study. The piezoelectric transducer reached an equivalent transducer sound-pressure level of up to 145 dB SPL and frequencies of 10 kHz. The dynamics for music reached 32 dB, which was identical with the results of the preoperative investigations using hi-fi headsets (33 dB). The low nonlinear distortions of around 0.1% and the frequency range up to 10 kHz are reflected in the positive evaluation of sound quality by 84% of the patients involved. The study is the basis for realizing a piezoelectric transducer designed for routine clinical implantations. The transducer is thought to be part of a totally implantable future hearing aid for rehabilitation of moderate and severe sensory neural hearing loss predominantly in the middle and high frequency range.