CC BY-NC-ND 4.0 · Laryngorhinootologie 2018; 97(S 02): S201
DOI: 10.1055/s-0038-1640407
Otologie: Otology
Georg Thieme Verlag KG Stuttgart · New York

Using the Floating Mass Transducer (FMT) as a microphone – a possibility to develop a fully implantable CI?

S Kaulitz
1  HNO Universitätsklinik Würzburg, Würzburg
M Cebulla
1  HNO Universitätsklinik Würzburg, Würzburg
A Bahmer
1  HNO Universitätsklinik Würzburg, Würzburg
R Hagen
1  HNO Universitätsklinik Würzburg, Würzburg
› Author Affiliations
Further Information

Publication History

Publication Date:
18 April 2018 (online)



Loudspeakers and microphones share common characteristics. Consequently, in early intercommunication systems loudspeakers were used as microphones. Utilising the FMT of the Vibrant®Soundbrige® (VSB) as a microphone has interesting potential applications such as within fully implantable CI.

Material and Methods:

Using an earcanal-eardrum-model, measurements were recorded using the FMT as a microphone via the Direct-Drive-Stimulator. Standard pure tone- and CCITT-signals from 250 Hz up to 8 kHz and Click- and Chirp-Signals were generated via an intra-aural earphone (EAR3A) and recorded and analysed using a professional Digital Audio Workstation (Studio One, Presonus). Additionally, soundtracks and speech-signals were also recorded.


The signal to noise ratio was good over the entire frequency range. Optimal sensitivity was obtained at 1,5 – 2 kHz and decreased at lower and higher frequencies. Recordings of music and speech-signals were also clear and comprehensible.


It is possible to use the FMT as a microphone. The frequency response is nonlinear which could be balanced in this setup using an EQ. The FMT as a middle ear microphone is an interesting new potential application. Temporal bone measurements are currently being performed.