Presented herein are directed to techniques for using objective measurements to determine a combined efficiency of an implantable actuator and a mechanical coupling of the implantable actuator to an auditory structure of an ear of a recipient. In particular, the implantable actuator is activated so as to deliver, via the mechanical coupling, mechanical stimulation to the auditory structure to effect a pressure change in an inner ear of the recipient. At least one stimulation device, that is separate from the implantable actuator, is configured to deliver secondary stimulation to the recipient to also effect a pressure change in the inner ear of the recipient. Objective measurements are performed to intra-operatively capture auditory evoked responses of the recipient in response to the mechanical stimulation and in response to the secondary stimulation. These auditory evoked responses are analyzed to determine a vibratory coupling efficiency.