Middle ear implants can be effective alternatives to in-ear aids for people with severe hearing loss. The major downside to embedding these devices is the invasive surgery required because of their large size. A collaboration of scientists from a number of German research institutions has developed a new middle ear device that makes implanting it easy.
The tiny transducer that generates sound vibrations can be implanted with a small incision in an outpatient procedure, as opposed to multi-hour operations that are considerably more dangerous. According to Fraunhofer Institute, the transducer takes advantage of “wireless, optical signal and energy transmission” coming from an external microphone. Plans are in the works to refine the original prototype and complete the entire system to begin testing it sometime next year.
“Our goal is to take the better sound quality of implantable hearing aids and combine it with a much simplified operation,” says Dominik Kaltenbacher, engineer at IPA. “To implant our system, all surgeons have to do is make a small incision at the side of the eardrum and then fold it forward. This can be done in outpatient surgery.”
The electro-acoustic transducer, which takes the form of a piezoelectric micro-actuator, is then placed directly at the connection between the middle and inner ear known as the “round window”. From there it transmits acoustic signals to the inner ear in the form of amplified mechanical vibrations, thereby enhancing the hearing capacity of patients. “The electro-acoustic transducer works on the same principle as bending actuators,” explains Kaltenbacher. “The bending elements, which are arranged in the shape of a pie, consist of a laminated composite made from piezo-ceramics and silicon. If voltage is applied, the elements bend upwards and generate a mechanical vibration. This spreads to the membrane of the round window and the inner ear, stimulating the auditory nerve.”
The effect: although the round window implant is no larger than a pinhead, it can output volumes of up to 120 decibels, which is roughly the noise a jackhammer makes. “This high performance is necessary for very good speech comprehension, particularly for high-pitched sounds, which people who are severely hard of hearing find especially difficult to pick up,” says the IPA researcher.