A noninvasive method and system are provided for assessing the performance
of implanted actuators of semi or fully-implantable hearing aid systems.
The invention utilizes an externally positioned measurement device to
obtain a test measure of the electrical signal passing through an
implanted actuator when driven by a test signal of predetermined
characteristics. In one embodiment, the measurement device may comprise a
pair of coils for measuring the magnetic field generated by an implanted
actuator utilized to simulate the middle ear of a patient. The magnetic
field strength is directly related to the amount of current passing
through the actuator. In turn, such current is inversely related to the
electrical impedance present at the implanted actuator. Such electrical
impedance is directly related to the mechanical impedance present at the
interface between the implanted actuator and middle ear of a patient. As
such, by driving an implanted actuator at one or more predetermined
frequencies the resultant magnetic field measures may be utilized to
assess whether the implanted actuator is operative and whether a desired
interface between the actuator and the middle ear of patient (e.g. the
ossicular chain) is present.