1. An at least partially implantable system for rehabilitation of a hearing disorder comprising: at least one acoustic sensor for picking up acoustic sensor signals and converting the acoustic sensor signals into corresponding electrical audio sensor signals, an electronic signal processing unit for audio signal processing and amplification of the electrical sensor signals, an electrical power supply unit which supplies individual components of the system with energy, at least one electromechanical output transducer which has an electrical input impedance and which, when implanted, is coupled via a coupling element to at least one of a middle ear and an inner ear for mechanical stimulation thereof, and means for objectively determining the quality of coupling between the at least one output transducer and the least one of the middle ear and the inner ear, said determining means comprising impedance measuring means for measuring the mechanical impedance of a biological load structure which, upon implantation of the output transducer, is coupled to the output transducer.