In those circumstances where a subject has conductive or mixed hearing loss due to inefficient sound transmission through the external and/or middle ear one system, one potential mode of treatment is direct acoustic cochlear stimulation (DACS). This involves the use of an implantable medical device incorporating an actuator which directly stimulates the inner ear fluid (perilymph) by simulating the operation of a normally functioning middle ear. In this way, a DACS actuator can circumvent damage to the outer and/or middle ear of a recipient to treat hearing loss.
As the DACS actuator is essentially replicating in whole or in part the operation of the middle ear, these devices are necessarily extremely finely balanced electromechanical systems. One area of sensitivity of these devices is their susceptibility to variations in the surrounding or environmental pressure conditions such as would be experienced where there is change of altitude or weather conditions. Accordingly, while a DACS actuator may be optimised for operation at sea level and normal weather conditions, a recipient may find the performance of the actuator affected by variations in these conditions leading to degradation in the performance of the hearing aid device.
It is desirable to improve upon any one or more of the above identified shortcomings.