Cochlear implantation can restore a certain degree of auditory impression of patients suffering from profound hearing loss or deafness. Furthermore, studies have shown that in case of residual hearing, patients benefit from the use of a hearing aid in addition to the cochlear implant. The presented studies aim at the improvement of this electromechanical stimulation (EMS) approach by substituting the external hearing aid by an internal stimulus provided by miniaturized piezoelectric actuators. Finite element analyses are performed in order to derive fundamental guidelines for the actuator layout aiming at maximal mechanical stimuli. Further analyses aim at investigating how the actuator position inside the cochlea influences the basilar membrane oscillation profile. While actuator layout guidelines leading to maximized acoustic stimuli could be derived, some of these guidelines are of complementary nature suggesting that further studies under realistic boundary conditions must be performed. Actuator positioning inside the cochlea is shown to have a significant influence on the resulting auditory impression of the patient. Based on the results, the main differences of external and internal stimulation of the cochlea mechanism are identified. It is shown that if the cochlea tonotopy is considered, the frequency selectivity resulting from the mechanical cochlea stimulus may be improved.
Keywords: Cochlear implant; Cochlear mechanics; EAS; EMS; Piezo actuator; Vibration analysis.