Mechanical, acoustic and electromagnetic evaluation of the semi-implantable middle ear hearing device (SIMEHD).

The properties of the partially implantable middle ear hearing device (SIMEHD) were extensively studied. The internal unit was subjected to 5,000 cycles of bending at a force of 75 g (gravity) without failure. An accurate measurement of the force output of the SIMEHD was obtained (14-25 dynes/mA). This force is too small to cause any damage to the ossicular chain. The force resulting from electromagnetic interference over a wide frequency range (500 khz -1 Giga (10(9)) Hz) was measured and noted to be within the margin of safety. The frequency response plots (500-8,000 Hz) were also obtained and revealed an excellent ability to amplify middle and high-frequency sounds.