Around 17 million people in Germany suffer from impaired hearing. A new device being developed at the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA), Stuttgart, Germany, can, researchers say, improve patients’ hearing and can be implanted during outpatient surgery. Hearing aids are a must for the almost one in every two people over the age of 65 in Europe whose hearing is poor. For those with severe hearing impairments, hearing can only be helped by an implant, which amplifies sounds more effectively than conventional systems and boasts better sound quality. But, middle ear implants require complex surgery lasting several hours, with high risk, and high costs.
The new device, being developed at IPA, is significantly easier to implant, making it affordable for large numbers of people. It is composed of three parts: a case with a microphone and battery; wireless, optical signal and energy transmission between the outer and middle ear; and an electro-acoustic transducer, which functions as the centerpiece and loudspeaker of the implant.
The electro-acoustic transducer is 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. The bending elements 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.
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 performance is necessary for very good speech comprehension, especially for high-pitched sounds, the researchers say.
The optimized individual components should be ready by June of this year, with testing of the overall system is planned for 2014, they say.
